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Written by Steve Remington, CollectAir © All Content

Well over a half-century ago, 60 plus years. September 8, 1952. My first day at Cessna Aircraft Company where I was newly employed as an engineer in the recently formed Helicopter Division. Introduced to Cessna by Mort Brown, Chief of Production Flight Test, and interviewed by Helicopter Division Manager Sherman Graves, Chief Engineer Charlie Seibel, and ONR Project Head Sanford Hinton, I was to spend the next ten years (with a two years timeout in the Army) on a variety of helicopter tasks ranging from wind tunnel testing through design and flight test. An exciting job for a new, slide-rule slinging engineer fresh from college sporting a barely worn pocket protector, I was confidently handed varied assignments with the implied assumption that each job would be accomplished without fail which was a far cry from the university scene and its graded-on-a-scale tasks. The work environment and engineering management in the Helicopter Division was stimulating for a young aeronautical engineer at age twenty-one, poised to vote for Eisenhower's first term. That fateful day in September can be verified(!) (with Cessna President Dwane Wallace's signature) by clicking here.

More than a half-century. That seemed like a long time when I was in my twenties but somehow has shrunken in significance as the years go by. To put it in perspective, however, consider this: when I began my employment with Cessna, the entire history of heavier-than-air development was less than a half-century! The brothers Wright had only began the wonderful era of flight 49-years earlier and it had only been twelve years since Igor Sikorsky, on May 13, 1940, managed to make short free flight hops in his VS-300 helicopter (see photo in "Afterword") and fifteen-years since Dr. Heinrich Focke flew his successful Fa-61 twin-rotor helicopter in Germany. No matter how you look at it, it was an infant industry, yet hundreds of helicopter designs had been advanced worldwide in those few years (estimated at 300 just between 1939 and 1945!).

Original artist's conception of the CH-1.

Design and construction started on the little known but record setting Cessna CH-1 helicopter in 1952 at the Pawnee plant of Cessna Aircraft Company in Wichita, Kansas. The drawing above is the original artist's conception of the CH-1; more on this later. Never a commercial or military success, the history of the Cessna helicopter program, with the handicap of it being conducted within an airplane-oriented company, is generally spurned and forgotten today by this business-jet based firm which answers to corporate legions psychically far removed from the world of ancient whirly birds.

Destined for obscurity, with fifty years elapsing since the complete demise and scrapping of the Cessna helicopter program, this article is intended to stake out a little corner of the remaining pages of helicopter legends and ensure that the remarkable CH-1 is chronicled with accuracy beyond the occasional "what became of" or "aviation failures" approach to journalism. This is not intended to be a dry, definitive history of the program, but a broad view of some of the background, highlights and warts, surrounding this rotary-wing endeavor which has survived extinction by only one known remaining machine buried away in dusty storage at the U.S. Army Aviation Museum. I don't pretend to have all the information on this program; my first hand knowledge is only of parts that I was involved with. There are lots of blanks. Anyone with information or corrections to add to this article is invited to submit their offerings to help create an accurate history; this article will always be subject to additions as readers offer their input. Sadly, at this point, fifty years later, many of the key players are deceased. I have listed as many of the Helicopter Division employees, engineering and shop, as I can come up with through 1962; this list appears in the "Afterword" of this article. If you can add names that I've missed for later years, 1961 through 1962, please let me know

Most reading this article are not engineers, but to give you an idea of why engineers think a little bit differently than most people, consider this quote by President Herbert Hoover who made this comment about engineers: "The great liability of the engineer compared to men of other professions is that his works are out in the open where all can see them. His acts, step by step, are in hard substance. He cannot bury his mistakes in the grave like the doctors. He cannot argue them into thin air or blame the judge like the lawyer. He cannot, like the architects, cover his failures with trees and vines. He cannot, like the politicians, screen his shortcomings by blaming his opponents and hope the people will forget. The engineer simply cannot deny he did it. If his works do not work, he is damned. . ."

Dilbert by Scott Adams

NOTE: Although copyrighted, this text, nearly in its entirety, has been hijacked by the web thieves at Wikipedia, without any attribution to myself. I ask you to not click on any advertising on the Wikipedia site - information on that site is usually stolen from the original authors.


Charles Seibel was the Cessna helicopter program. A dynamic engineer, with a 1943 Masters Degree (Engineering - Helicopter Theory) from California Institute of Technology, part genius and part clown, with a very affable nature, but demanding, and with seemingly unbounded energy and enthusiasm for rotary-wing development, Seibel's ideas were meticulously translated into drawings and metal by the small Cessna staff. He encouraged original thinking by his engineers and prodded engineering minds to explore new avenues. Let's take a look at how Seibel (pronounced "See-bull") became part of the Cessna team.

A young engineer at the Gardenville, New York (a suburb of Buffalo) factory (a rented shop) of the early Bell helicopter, having been hired in June 1943 by Bob Stanley, Bell's Chief Test Pilot, Siebel worked on the Bell Model 30 project. While at Bell, Siebel decided to design his own, simplified and inexpensive helicopter. Living in Kenmore, N.Y., near fellow Bell employee Dick Ledwin, they began building the S-3 helicopter in the attic of the duplex building where Charlie lived. In 1945, the helicopter group moved to the Niagara Falls plant where work was commencing on the Model 42 helicopter. Note: During this period at the Niagara Falls facility, Bell was working on the XS-1; beginning with the mockup in April, 1945, the first XS-1 was rolled our near the end of December, 1945; without engine, this ship was first destined for glide tests. A Renton B-29, 45-21800, was modified to accept the XS-1 which made the first flight on January 25, 1946.

Bell Gardenville plant in 1943.

Bell Model 30 helicopter at Buffalo, New York on its maiden free flight, July 29, 1943,with Art Young at the control.

Bell Model 30, NX-41867, in NASM collection at Garber Facility - was rebuilt after crash and redesignated serial #1A -CollectAir photo.

Bell 30 "Genevieve" now at Steven F Udvar-Hazy Center - CollectAir photo 6/05.

Fighter test pilot Floyd Carlson in the Bell Model 30, obviously in the winter. Note that this is the early version of the cyclic control which has the throttle grip on the cyclic. Carlson,like Arthur Young, had no helicopter experience and learned to fly the Model 30 on a tether. Carlson became Bell's chief test pilot for the helicopter projects, and the only pilot until Joe Mashman, a Bell fixed wing production test pilot, was assigned to the helicopter division of Bell. Mashman had no helicopter experience at that point. Bell photograph 203456.

Dick Ledwin can be seen in a Bell photo of the Model 30 taken on November 15, 1946 by clicking here. Click on photo to enlarge - use the back arrow to return.

A video featuring Arthur Young and early Bell Model 30 flights may be viewed by clicking here. Use the back arrow to return. Note that the Model 30 shown is NX 41868, the follow-on to 41687 pictured above.

Seibel S-3 helicopter at Wichita, Kansas. This is the later version of the S-3 that incorporated conventional cyclic control.

Charlie decided to leave Bell in September 1946, departing the winters of upstate New York for the Mid-West, he moved with his wife Thelma and young son David, to Wichita, Kansas where he had graduated from high school, took a job as an aerodynamicist with Boeing on the XL-15 and continued work on his own S-3 design, building the innovative light helicopter in his basement with his friend "Red" Lubben who departed Bell to join with Charlie. Dick Ledwin, still in New York, machined parts for the S-3 from drawings sent east by Seibel.

Boeing L-15 Scout, Model 451.

In 1943 Seibel had made preliminary designs and patented (March 1944) his first design, the S-1, which was a twin tilt rotor that looks amazingly like the current Bell VS-22(!) - the idea preceeded his Bell employment so the patent was his. The next Seibel design, the S-2, was a co-axial design study that he shelved. He launched his first helicopter, the S-3, at Wilson Field in September 1947 for its first hovering lift-off. This design had been tested in model form, as shown below in a 1947 photo. The tethered scale model approach had previously been successfully used by the brilliant designer of the Bell Model 30 helicopter (pictured above and the genesis of the Model 47), mathematician Arthur M. Young, and Seibel obviously followed this example of a man whom he highly respected. Seibel had extensive experience at Bell operating a control-line helicopter model during testing. (The use of control-line or tethered helicopter models was more widespread than just Bell or Seibel. The used of tethered scale models for full-scale aviation research was used by many researchers, not only in the past, but currently as well. The well known Igor Benson, later of autogiro fame, worked as the Chief of Research at Kaman Aircraft Corp. in the early 1950s concurrent with Charles Seibel's helicopter efforts in Wichita. Under Benson's direction, as many as twenty models were tested, powered by compressed air, electric motor, and gas engines; a tip jet "microlaboratory" Kaman K-6 model was featured in the May 1952 issue of Air Trails magazine.)

The S-3 incorporated the Seibel-designed simplified control system wherein a moveable cabin section shifted in response to "cyclic" stick inputs thereby shifting the center of gravity and causing the machine to respond accordingly. This machine, NX735B, is pictured below as it appeared in a magazine fold-out from the May 1948 issue of Air Trails Pictorial (the Boeing L-15 appears on the other side of this foldout - this issue has one of the best articles, entitled "Basement Helicopter", appearing in any magazine of the era on the Seibel design and his efforts) and on the cover of the American Helicopter issue for December 1948 which shows the S-3 with cyclic control being flown by test pilot Johnny Gibbs. Charlie flew this machine in hover for about 8 hours without having any previous flight experience prior to obtaining the services of qualified pilots. The book, "Borne on the South Wind", by Rowe and Miner, 1994, has a few paragraphs on Seibel and the Cessna helicopter.

The October 1948 issue of MECHANIX ILLUSTRATED featured Seibel's helicopter on the front cover with the caption, "Builds Helicopter From Truck Parts - See Page 64."

Two pages of pictures and some text were devoted to the project. The entire text is reproduced here: "He Built a Helicopter in His Cellar. When Charles Seibel of Wichita, Kansas, broached his idea for a new-type helicopter to an aircraft company, they laughed at him - said construction alone would take a quarter of a million bucks.

"So he retired to his own cellar and started building. At the end of seven months he had an egg beater which flew easily and was cheap to operate and maintain. And it cost him less than $5,000.

"Seibel used Ford truck gears and clutches, odd pieces of sheet metal, aluminum tubing, wood and wiring picked up at war surplus stockpiles.

"When testing day came, he had no test-pilot so he flew it himself - successfully! And he had never flown a plane before in his life!"

CAPTIONS: "Seibel first built this model to prove his ideas. Test flight: Seibel squeezed his 6-foot frame into his helicopter. Flew it himself while family watched. Cellar Factory: In this basement workshop Seibel built his "impossible" helicopter. It was made in 3 parts so it could be removed from the cellar without having to be disassembled. To start the 65-hp Franklin engine, below, he spins it with a cord like an outboard motor (see photo above that went with this caption). Control: In his unique system the fuselage splits and moves backward or forward, changing the center of gravity of the ship and causing it to climb, lower left, or glide, lower right." Some good publicity at about the time Charlie was courting investors!

The moveable c.g. concept was subsequently abandoned on the S-3 (insufficient control and the potential for roll-over on hard landing) and a more conventional cyclic control system was installed for continued testing and promotional flying. The Seibel Helicopter Company was formed with investors from the local oil industry in 1948. Quiting his job with Boeing to work full-time on helicopter projects, the Seibel S-4, a 2-place ship, was a follow-on development utilizing a similar control system as the later S-3 and incorporated Seibel's rotor system using stacked, stainless steel "L" shaped blade attachments which carried all rotor loads and flexed for control input thereby eliminating blade pitch bearings. Also, the ship used a supercritical tail rotor shaft and simplified ring and pinion transmission. The S-4 first flew in early January 1949 with a heavy schedule of test flying for test pilot Johnny Gibbs who had a helicopter background doing crop dusting. The S-3 was still being used as a promotional demonstrator until early 1949 and it was dismantled, having accumulated 100 hours - three "pilots" had flown the S-3 (Johny Gibbs, Bob Elliott and Charles Seibel), only one of whom (Johny Gibbs) was licensed as a rotary wing pilot and had previous helicopter experience as a crop duster. The Seibel Helicopter Company moved from their Wilson Field facility to a North Broadway building (5613 No. Broadway) in the fall of 1949 and made application for a type certificate, only the 5th company in the U.S. to do so. Dick Ledwin departed Bell and joined Seibel.

Seibel S-4 Helicopter. Simplicity plus!

Certification tests were completed in March 1950; the flight test engineer from the C.A.A. on this project was San Hinton who later became part of the Cessna program. The S-4 received C.A.A. Type Certification on April 23,1950 during a celebration of the big event at the Wichita Municipal Airport - attending the ceremony was Dwane Wallace, Al Mooney, Earl Shaffer (Boeing) and Walter Beech - and the S-4 was demonstrated on a very, but typical, windy day. A larger engine, a Lycoming O-290B of 125 h.p., was subsequently installed and certificated as the S-4A with Hal Hermes as the C.A.A. test pilot. The S-4A won a contract with the Army for an evaluation quantity of two ships as the YH-24.

The first, 51-5112, was delivered in April 1951 to Fort Bragg, N.C.; the second YH-24, 51-5113 to Wright Field. The YH-24 failed to win Army approval and the two ships were later scrapped by Cessna in 1952. The single control YH-24 couldn't be used for training, so that deficiency prompted Seibel to design a new version, the S-4B in only two months. The Seibel S-4B embodied a side-by-side arrangement with skid gear and was fitted with a larger engine, the Franklin 6A4-165-B3 of 165 h.p. The S-4B was a rather basic helicopter layout with an undistinguished appearance yet it embodied the important design basics of rotor, drive system and control that would become incorporated in the Cessna CH-1 in the future. During the summer of 1951, Jack Zimmerman (who had been flying helicopters in Alaska) was hired at Seibel Helicopters as test pilot - he would become the Chief Test Pilot for the Cessna program. The S-4B was demonstrated at Fort Sill, Oklahoma after being completed in only two months and it received a glowing report from that Army Air Training Department in October 1951. Nevertheless, lack of capital prevented the Seibel Helicopter Company from pursuing further Army business, by this time having moved again to 3400 North Broadway adjacent to grain elevators (see photo below)!. The S-4B was never certificated and remained in the experimental category.

Seibel S-4B helicopter - 1951. Jack Zimmerman and U.S. Army pilot.

Jack Zimmerman in S-4B with U.S. Army pilot.

Jack testing S-4B with wheels instead of skids - 1951.

Hover demo of S-4B. Dick Ledwin standing at left, 2 employees under engine (!), and Jack and Charlie in cockpit.

Charlie Seibel in center with Dick Ledwin on his right and Jack Zimmerman on his left. The guys on the ends were the "ballast". This photo shows all of the company's employees!

Looking ahead to possible future military programs, Dwane Wallace, president of the Cessna Aircraft Company, was attracted by Seibel's local Wichita efforts and was instrumental in effecting a stock swap with the Seibel investors in the Seibel Helicopter Company by January 14, 1952. The Wichita Eagle newspaper carried a headline that day, "Cessna Moves to Take Over Seibel Helicopter Production." in March, 1952 all equipment, including the S-4B, were moved to the Pawnee Plant of Cessna.

Jack Zimmerman and Charlie Seibel delivering Seibel S-4B, N5154, to Cessna. Note that both are dressed in business suits - appropriate for this transfer of assets to Cessna. Photos of Seibel S-4B courtesy of Hal Zimmerman.

Seibel S-4B at Cessna. Helicopter Division General Manager Sherman Graves received his first helicopter ride in this machine. The S-4B was used for helicopter familiarization flights for a few months. Photo from Seibel film/video.

From the June 1952 issue of "Flying."

Personnel were hired or transferred from other departments and work began on the CH-1 design during the summer of 1952. The Seibel S-4B, N5154, was flown for several months to familiarize Cessna with helicopters, and then scrapped. Note that the Seibel S-4B "N" number was N5154; the first Cessna testbed CH-1 was N5155, a carryon of the Seibel "N" number sequence. Seibel believed that the S-4B with some Cessna aluminum wrapped around it would have made an excellent and inexpensive trainer for the Army. This would not happen.

Charles Seibel - a 1957 photo.


The artist's drawing shown above was the origin of the final CH-1 design; it was drawn by an industrial designer, Richard Ten Eyck, who consulted on most aircraft designs for Cessna. It has obvious airplane characteristics: engine in front, streamlined body, cabin seating behind the powerplant, low profile, and, in general, a sleek, non-helicopter appearance. I do not know exactly how much input Seibel had in this external design configuration but it was jelled between April and Summer 1952 from initial sketches (showing military markings!) which were for a slightly smaller cabin - possibly made by Seibel.

A preliminary sketch of the Cessna CH-1 from Seibel film/video. This sketch shows the general layout of the CH-1 but appears to be a two-place version, obviously aimed at the military from its inception!

Richard Ten Eyck reconfigured the fuselage to the final shape, large enough for a four-place. He also later helped shape the master plaster mold for the fuselage and cowling. Unlike so many aviation projects, the actual prototype CH-1 looked almost identical to this drawing. The forward engine location had some advantages such as maintenance accessibility, cabin visibility and c.g. control (permitted occupants to be near c.g.) but it also presented a problem of what to do with the exhaust, a complication that plagued the ship throughout its brief life and spawned numerous "solutions", none of which were really successful. Also, the airplane-style fuselage, although nice looking, resulted in a tail boom volume that was much too large in hover flight and required aerodynamic solutions to overcome, particularly because of pitching moments in forward flight caused by the streamlined body.

The engine-in-front configuration was certainly not unique; it was used very successfully by Sikorsky on the S-55 and S-58, and the Russian Mi-4 "Hound", where the heavy reciprocating engine was in front and the payload located on the c.g. However, the radial engines, as used on these helicopters, permitted the exhaust gas to be collected and exhausted at a convenient location which avoided grass burning and carbon monoxide contamination in the cockpit. The earliest front-engine helicopter also had a radial engine; the German Flettner, single rotor, Fl 185 flew in 1936 with a 140 h.p. Siamens-Halshe Sh 14A radial. The Fl 185 was partly a convertiplane with rotating stub wing tip propellers that also served as anti-torque rotors. In about the same time frame, the Soviet designer, Ivan P. Bratukhin, working at the Russian aeronautical laboratory, TsAGI, doing development and prototypes, designed a very similar front-engine helicopter (radial engine) with a single rotor and anti-torque rotors at the tips of stub wings; the Stalinist purges hindered development and the machine was redesigned in 1938 (the 11-EA PV) with tubular outriggers replacing the stub wings, each outrigger with two anti-torque rotors in tandem, sort of a compound helicopter. The first free flight of this ship was in 1940 but the combination of parts problems for the Curtiss Conqueror engine and Soviet disinterest doomed the project which was halted in the Spring of 1941. As a follow-on to the Fl 185, Flettner developed the intermeshing rotor Fl 265, using a front-engine 7-cylinder radial, which first flew in May 1939. This single-seat Fl 265 was service evaluated and six prototypes were built - the first "production" of a front-engine helicopter - pictured below.

The Brazilian government sponsored a helicopter design within its Departamento de Aeronaves; developed over a four year period beginning in 1954, the ship made its first flight at the Technical Center for Aeronautics in Sao Jose dos Campos on January 22, 1959. Designed by the German engineer Dr. Heinrich Focke (the first to design a successsful helicopter, the Fa-61) and his German staff (ex Focke-Wulf), the Beija-Flr BF-1 was a 2-place with a design somewhat similar to the Cessna CH-1 - flat Continental 225 engine in front and the rotor mast running vertically between the front seats. This ship was test flown but doubt whether it went into production. Do you suppose Focke might have got the idea for this configuration from the CH-1?

Four-place version of the Brazilian BF-1.

Mention should also be made of the Italian Lualdi L-59 4-place helicopter which had a front-mounted Continental 470 engine; two helicopters were built by Macchi for military testing by 1962.

Lualdi L-59.

The earliest American light helicopter with a forward mounted engine that pre-dates the CH-1 was the Aeronautical Products, Inc. (API) 1944 Model 3 of Detroit; loosely based on a lightplane, the nice looking Model 3 was powered by a Franklin 6AC-298 and had a drive system similar to the CH-1. Only one ship was flown for a short time. It is not known whether the API had any influence on the basic layout of the CH-1 (see diagram below).

The API Model 3 of 1944. Built in Detroit.

The API helicopter designed by Corwin Denny and Karl Schakel. Note the nifty P-38 in the background with pre-1947 USAF marking.

Another view of the API.

The Teicher-Hunt Humming Bird had a similar drive system layout. The Teicher Hunt Helicopters company of Brooklyn, Connecticut was headed by W.E. Hunt in 1949. Hunt had been a Sikorsky project engineer on the XR-4 and XR-5. The firm designed a front engine, single rotor helicopter which reached the prototype stage.

Sketch of the Teicher Hunt Humming Bird drive system from the 1954 publication, "Mechanical Design and Description," by Harris Campbell and edited by Eugene Liberatore of the Prewitt Aircraft Company. Office of Technical Services document PB 111632.

The T-H Hummingbird design was later purchased by Glenview Metal Products and William Hunt was retained as a consultant. The helicopter underwent some redesign and a larger engine installed. The Glenview Metal Products "Flyride", was then a contemporary of the CH-1, with the prototype flying by 1954. This New Jersey helicopter featured a 135 h.p. Lycoming engine, was a two place, and had a simplified control system. A ship with a pleasing appearance as pictured below.

The GMP-1 Flyride - 1953.

Another front-engine design that I've only recently run across in the 1960-61 Jane's, the obscure Haig-K Aircraft Corporation HK-1 pictured below. The Continental C85 is practically in the pilot's lap!

Two prototypes of the front-engined "Grasshopper" were built in the U.K. by 1962; the ship had counter-rotating rotors and two 100-hp engines. Looks a little "nose heavy".

U.K. "Grasshopper."

And, for the most bizarre approach to a front mounted engine, the French company MATRA flew this machine in 1953, designed by Mr. Cantinieau, in the same time frame as the Cessna Skyhook design effort. "Oui, each pilot has a stepladder in his flight bag in order to check the oil!"

A quarter-size wind tunnel model of the CH-1 was tested at Wichita State University. Drawings were being produced and metal being cut for static tests and a dynamic, flying test bed early in the program. I have the original memo which outlines the program and the schedule through February of 1953. This first machine did not have an enclosed fuselage or cowling - a true flying test bed. The memo, in part, states;

"The first helicopter CH1-1 is being built for the following purposes:

"1. To serve as a mock-up for control systems, fuel systems, etc.

1952 wind tunnel model of CH-1.

"2. To place machinery (clutch, free wheeling unit, transmissions, and rotor systems) into operation at the earliest possible date in order to uncover mechanical deficiencies, design errors, etc.

"3. To serve as a flying test bed to investigate hovering control and stability and other slow speed flight characteristics.

"4. To serve as a flying test bed to investigate rotor system stresses and vibration characteristics.

"5. To allow initiation of C.A.A. certification testing of the helicopter drive and rotor systems at the earliest possible date."

Drive system test stand with club rotors and flying test bed - 1953.

Jack Zimmerman flying the CH-1 test bed, N5155, Ship #1.

I came on this scene in 1952 at a time when an engineer was needed to assist project engineer, Sanford Hinton, with a U.S. Navy Office of Naval Research (ONR) helicopter research contract which had been obtained by Cessna; a system of rotor blade suction boundary layer control was to be designed and flight tested for effectiveness in delaying retreating blade stall on a Cessna CH-1 helicopter (which was only a paper helicopter at the time the contract was signed!). The announcement of this ONR contract was made in the August 22, 1952 issue of the Cessquire company magazine as presented below.

I tested two-dimensional oscillating blade sections, with varying degrees of BLC, in a four-foot wind tunnel at Wichita State University and did preliminary design work on a complete BLC system for the CH-1. I was taking a wind tunnel course at the university, using the same tunnel that I was designing a test installation for! Talk about on-the-job training. More on the BLC later in this article. The helicopter group was crammed in a second floor office at the rear corner of the main Pawnee production plant; we overlooked the small Cessna field, grass with a tiny runway aiming right at McConnell AFB, and B-47s from the AFB noisily whizzed by our windows on their take-offs from the field shared by Boeing and the Air Force. Boeing Wichita was building the B-47E and the RB-47E in 1953; the 1000th B-47 (tail number 2609) was built at Wichita in October 1954. Just below the office, a tail rotor test rig whirred away night and day, the CH-1 was being constructed and the giant rivets for all the Cessna airplane wing struts were bucked right below us. In addition to the light single-engine airplane production line (Cessna had no twins in production at this time), giant tail assemblies for the B-47 were being built, along with sections for the T-33, F-94C and F-84F under subcontract by Cessna; a real Mutt and Jeff situation that I got to see on my passage each day as I walked the production line to our office. I witnessed an important event in Cessna history on January 3, 1953, a Saturday afternoon, as test pilot Hank Waring lifted the new prototype 310 off the AFB runway under a cheery winter sun for a 30 minute first flight. A little more than a year later I became a guest of the U.S. Army, still doing helicopter work. The helicopter development group moved to and became part of the Military Division (T-37s) at the west side Prospect Plant (Cessna was awarded the development contract for the Cessna Jet Trainer Model 318 in January, 1953) and the original division manager, Sherman Graves, was tragically killed in a freak Cessna 170 ground collision with a DC-3 in Richmond , Indiana in December 1952 (see newspaper clipping below) and later, in the Spring, replaced by Jack Leonard who came from Goodyear.

Sherman Graves. Photo from Seibel video.

Taken from the "Cessna 1941 AirCrafter" yearbook.

Jack Leonard in a 1956 photo.

First T-37 model in ten-foot wind tunnel - 1953

The test bed skeleton of the CH-1 first hovered in July, 1953 (this test bed flew as high as 10,000 feet and later became the basis for the second prototype, Ship #1, N5155, with perhaps a fuselage from the static test ship) and the prototype CH-1 was tested at the Prospect plant, N5156 (ship #2) making its first flight in 1954. Of interest, this first prototype did not have a horizontal stabilizer and flew extensively before one was added - no publicity photos were released of this initial version that I know of. The photo below of the prototype without horizontal stab was taken from a 16mm film; Seibel made film records of most of the CH-1 premier events.

Cessna protoype without horizontal stab. Seibel film/video.

Prototype in-flight photo from Cessna. Seibel film/video.

Prototype CH-1 performing Height-Velocity (HV) landing tests. Seibel film/video.

Dick Ledwin (now deceased) was the shop manager and he and his crew worked magic when it came to building prototypes. I was in the Army at the time and took the photo below from an L-19 in August 1954 on a foray from Ft. Sill to Wichita. Shown on the tie-down test stand is N5156, still ten months from C.A.A. type certification - there is no horizontal tail on this ship. The next photos show N5156 in flight, in black and white and in color, both distributed for publication purposes and widely printed in magazines, newspapers and other journals at the time.

CH-1 N5156 pictured in green scheme with Jack Zimmerman's young son, Hal, standing alongside in about 1956 or so; note modified exhaust outlet ducting. Photo courtesy of Hal Zimmerman; Hal has kindly provided many photos of his dad which are used on this website.

L to R: Charlie Seibel, Jack Leonard, two Army brass, pilots Jack Zimmerman and Robert T. Shaw (Oct 2010: I was contacted by Sue Shaw, Bob Shaw's daughter, with information that her father is deceased). The interesting thing about this photo is that it shows both CH-1A prototypes, N5156 (green) and N5155.

Jack Zimmerman and Ship #2, N5156, in a fly-in interview at local TV station KAKE.

More photos of the prototype CH-1, N5156, are shown below during a publicity photo shoot. The paint scheme was a temporary livery. Can you identify the car?

Click on the Flying Farmer magazine cover from September 1954 for a full size PDF file for the cover, suitable for printing.

The prototype CH-1 had a Continental FSO-470 engine rated at 260 h.p. at 3200 rpm equipped with a belt driven supercharger and belt driven cooling fans. It should be mentioned here that Cessna was using Continental engines exclusively at this time - the company would not even consider a flat Lycoming engine. An airplane with a Lycoming engine was always lurking in the experimental hangar reportedly just to keep Continental on their toes. The CH-1 was going to have a Continental engine no matter what else was available. The high rpm, big bore Continentals were unproven in production aircraft so we were a test bed.

Portion of Continental ad from December, 1954. Copy reads, in part, "New, modern helicopters are finding it increasingly beneficial to make use of the latest Continental developments for power production. Two examples of recently tested engined built around Continental power plants are shown. One - the Sikorsky XH-39 at left, above - employs the CAE Model 220 shaft turbine; the other - Cessna's CH-1 at right - uses CMC Model FSO470 piston engine. Both are unique. The CH-1 features simplified design, using one-third fewer gears. Location of engine in the nose makes for ease of access, promotes efficient cooling, and frees the center of gravity behind the cockpit for use in disposable load."

1954 Cessna Helicopter Division Christmas Card

Collector card in the "JETS1 Spotter Series" from the 1950s. This 53x75 mm card shows the familiar photo of the prototype and states on the back that, "Cessna CH-1 is a new helicopter undergoing CAA tests...development required 2 1/2 years." Note that this is card No. 1 in the series.

Photo of the first prototype Cessna XT-37, 54-716, flying from the Wichita Municipal Airport. The first flight was made on October 12, 1954 by pilot Bob Hagan. One of two prototypes, the XT-37 was lost in a flat spin; the pilot baled successfully but the airplane "splatted." The result: fuselage strakes and the ventral fin designed by an aerodynamics whiz in military engineering.

First flight of the XT-37 piloted by Bob Hagan.

Cessna advertisement, March 15, 1955.

Factory concept drawing of T-37.

The engine exhaust exited under the helicopter with little noise attenuation. Project Engineer Bob Smith recalls the noisy exhaust on the early CH-1; "Jack (Zimmerman) complained about it right after the completed CH-1 started flying. Mel Vague and I went out to the tie-down area one afternoon to record sound readings and the temperature and humidity to correct the sound measurements. We didn't have hearing protection in those days. Jack was right! It felt like someone sticking needles in our ears! Anyway, the dB level corrected to 141; the temperature was 114 degrees F and the humidity was 3%. Good old Kansas summertime. This dB level was way above the Fletcher-Munson curve which showed the levels above which permanent hearing loss was probable. Right after that we started in earnest to design a muffler; I guess we never did get it right."

Cessna released a drawing in 1:20 scale of a 3-view of the CH-1, complete with sections, in about 1955. This drawing could be used to construct a scale model. The side view shown above is a part of this drawing - a little yellowed with age. The drawing measures 16" x 36".

The 3,000 lb. gross weight CH-1 received C.A.A. type certification, 3H10, on June 9, 1955; the new helicopter had the highest never-exceed-speed of any certificated helicopter, 122 mph (although at a reduced gross weight), and a maximum gross weight hover ceiling of 11,000 feet, exceptional numbers for the time. The CH-1 was certificated as a two-place helicopter; longitudinal stability problems at aft c.g. caused by the pitching moment of the streamlined fuselage required additional engineering and test work on the stabilizer system. The floating stabilizer stop was then linked to the lomgitudinal control and the CH-1 was then quickly certificated as a four-place and designated the CH-1A on February 28, 1956.

The ink wasn't dry on the type certificate before a record flight to Pike's Peak was made with the CH-1 and work began on the "B" model directed at even better performance with an improved engine with a military contract in mind. Continental couldn't attain sufficient belt life for the original engine and suggested a change to the FSO-526.

The following information is from the 1955 Cessna CH-1 brochure, shown above, in order to give an idea of the selling points being promoted. It wasn't intended that this basic CH-1 model would ever go into production, but this brochure certainly gives the impression: "Smart and trim, the CH-1, first Cessna helicopter, having advantages never before offered in a helicopter, employs a single lifting rotor and a single anti-torque tail rotor. Both fuselage and rotor blades are metal, combining high utility with minimum upkeep.

"Sturdy skid-type landing gear allows landings on all types of terrain. Snap-on wheel assemblies save ground handling time. The tail rotor is elevated to safeguard ground personnel and permit the CH-1 to operate in heavy brush.

"For easy installation and servicing the supercharged engine is mounted in the fuselage nose. This location also gives added cargo and passenger space in the fuselage around the main rotor shaft.

"Unusually smooth control operation is acheived through a simple, totally enclosed rotating control assembly and the aero-dynamically clean rotor assembly. A control boost system, supplied as standard equipment, eliminates cyclic feed-back to the pilot's control stick. The angle blade attaching member and spiral bevel transmission gears combine to give long operating life to the drive system."

On September 13, 1955, at 7:00 a.m., the CH-1, N5156, now certificated, landed, hovered and took off with two and three persons from Pike's Peak, Colorado, an elevation of 14,110 feet, the first helicopter ever to do so (the highest in North America). These flights were conducted with a representative from the U.S. Army to demonstrate the CH-1's amazing altitude performance capabilities, such performance totally lacking in the Army's fleet at the time and in civilian use by supercharged machines as well. The photos below were widely distrbuted by Cessna and the flights received good press. Cessna test pilot Jack Zimmerman (now deceased; Jack was a WWII helicopter pilot flying Sikorsky R-4s) was the pilot for these flights and flew off the Peak with Captain Knowles of Fort Carson and then with the commanding general of Fort Carson, Major General Van Houten. An altitude of 17,600 ft. was reached during these Colorado evaluation tests with Captain Knowles. Tests with Army personnel were conducted at Camp Hale, Colorado where Zimmerman and Captain Knowles made landings on Horn Silver Mountain (11.300 ft.), Ptarmigan Hill (12,154 ft.) and Sugar Loaf Peak (12,567 ft.). Bell Helicopter became aware of Cessna's program to land on Pike's Peak and made an attempt to beat the CH-1 with a Bell 47G-2; coming in second, Bell landed on the Peak later on that same day! Details of the helicopter landings on Pike's Peak appeared in the Denver Post evening edition that day.

CH-1A in the Rockies; from a 16mm movie frame.

Jack Zimmerman (RH seat) and Captain Knowles during altitude tests. Cessna's Dick Ledwin checks over the ship.

Bronze relief plaque commemorating Pikes Peak landing. I took this poor photo at the Wichita Air Museum. There is supposed to be a plaque on Pikes Peak; does anyone know if this is true? The plaque inscription is as follows: "SEPTEMBER 15, 1955 PIKES PEAK 14,110 FT. CESSNA CH-1 HELICOPTER. First successful landing and take-off ever accomplished by any aircraft from this peak was on September 15, 1955. The aircraft was a Cessna CH-1 helicopter manufactured by the Cessna Aircraft Company, Wichita, Kansas." Correspondent John Davis of Wichita has written that, "Bob Pickett - who was Cessna's unpaid historian - and who had the Pike's Peak plaque in his collection, always said that it was the only one, and that Cessna could not get approval to install it on the mountain because of Federal regulations."

This is the exact Bell 47G-2 that Hersey Young landed on Pike's Peak following the CH-1. Hersey picked up this G-2 at Bell on June 17, 1955 and participated in a dedication of Stapleton Field on June 19 with a demonstration carrying a passenger to 16.100 feet. The G-2 was powered by a non-supercharged Lycoming VO-435. Hersey is at the controls in this photo which was taken at Bell. This was only the second G-2 delivered, the first going to France on May 30. Jean Moine took that ship to a record in France by landing and taking off with a passenger from the 15,771-foot-summit of Mount Blanc in early June, 1955. Unfortunately there was no similar height available in the U.S. for demonstration!

Landing on Pike's Peak became popular following the Cessna and Bell ventures. Major Walter S. Makuch, in the Army H-21C helicopter 52-8686, landed on Pike's Peak on March 20, 1956; shortly afterwards, three H-21C,s from the 93rd Transportation Company (Light Helicopter)(H21), then based at Fort Riley, Kansas, perched on the 14,110 mountain top. This landing, I believe, was the first at this altitude by an Army machine.

The spacious cabin of the CH-1 was promoted using company publicity photos; a few typical interior scenes are presented below, both from 1955/56.

This cockpit scene is probably the CH-1B, not the CH-1A.


Work commenced on the CH-1B during 1955, really a design change aimed at the military, using a Continental FSO-526 engine (derated to 270 h.p.) with a gear driven supercharger and a newly designed horizontal, gear driven cooling fan. The Continental FSO-470 of the CH-1 proved to have unreliable belt life for the supercharger/fans and the FSO-526 was an option because the Cessna four-engine 620 used a similar engine. Other improvements were made to the "B" model as well, including a larger, constant chord moving stabilizer. The stabilizer free floated to a vertical position during hover and pivoted to a stop during forward flight; the stop was connected to the fore and aft cyclic control thereby altering the stabilizer incidence during flight. Also, an automatic collective pitch reducer lowered the collective pitch in the event of an engine failure. The rotor speed was increased by changing the transmission ring gear from 51 teeth to 49 (pinion gear had 6 teeth).

Cessna ad in the March 15, 1955 "Aviation Week".

One incident in 1955 with the CH-1 is a reminder of the amazing flying skill that test pilot Jack Zimmerman brought to the program.

I previously wrote an account of Jack's handling of an in-flight failure of a blade pitch horn based on my dim recollection of the events as described by Jack. I was in the Army at the time so only had conversations to rely on to tell the story. Fortunately, Sid Shannon, Sales Manger at the time, the passenger with Jack, has filled me in on the details of the event, the facts of which are no less exciting and amplify the circumstances leading up to the failure. Here is Sid's description (dated September 28, 2007): "Your story on the Cessna CH-1 is fairly complete but there is one item missing that ties the sale of the helicopter to the military. In June and July 1955 the CH-1 was flown to Washington, D.C. to demostrate it to the various branches of the service. On June 21, on the last leg of the flight to Washington from Columbus, Ohio, the failure of the Pitch Arm that is covered in your story occurred and caused a forced landing near the town of Cadiz, Ohio. I had been flying the helicopter until just a few moments before it pitched up and sideways very violently. Jack Zimmerman was fighting the controls but was having difficulty and after a few moments said he could not hold it and to get out. It took a moment to unbuckle the seat belt, open the door and crawl out over the collective control stick (passenger sits in the left hand seat on the CH-1) onto the the skid, and during tht time the forward speed had diminished a great deal; I stood on the skid, holding the door open, looking at Jack and as the speed decreased some semblence of control returned and Jack said to get in and help find a spot to put down. Already being a member of the Caterpiller Club, having bailed out of an Experimental Bomber at twenty-six thousand feet, I felt no need for a second membership and got back in and helped locate a landing spot. The helicopter was not flown to Muskegon for discussions on the engine, but several trips were made by plane.

"Jack Leonard and a couple crew members were flying in a 195 chase plane, but had gotten out of radio range so it took a few minutes to get in touch by radio relay with other pilots and ATC. He finally returned to Cadiz, we got to town and found quarters, found a good machine shop where we could do our repair, and Jack Leonard flew back to Wichita to get Dick Ledwin. When Dick and Jack returned, it took a couple of days to make the repairs and after some ground tests of the rotor, we continued on to Washington on June 24.

"Demonstration flights were made at Ft. Belvoir, Ft. Monroe, Baltimore Harbor and Annapolis until July 24 when we started our return trip to Wichita. Demonstration flights were made at Wright Field to the Air Force and we returned to Wichita on July 30.

"Shortly after arriving home from Washinton we took the helicopter to Colorado Springs for testing at altitude and about this time we received our order from the Army for helicopters. At this time it was decided that no orders would be taken for more helicopters until the Army orders had been fulfilled and experienced had been gathered. There seemed little excuse for having a Sales Manager and I resigned and left Cessna."

A pitch horn casting had failed causing the above described emergency situation. The blade attach angles had forced the blade pitch to a "neutral" postion for that blade thereby allowing flight, albeit rather scary, without any control attachment for one of the two blades! Try that on any other helicopter flying at the time. Future pitch horns were made of forgings. No panic, just cool flying and doing what ever necessary by assessing the situation and taking corrective action - that was Jack Zimmerman.

Lt. Jack Zimmerman, U.S. Army Air Corps - 1944. I have attached a biography of Jack which may be accessed here by clicking Jack Zimmerman Biography. Jack's WW2 experiences with the Sikorsky R-4 helicopter are included in this biography.

Cessna was awarded an Army contract for $1.1 million to build ten ships, designated as the YH-41 Seneca, for military evaluation purposes, this contract being signed in the spring of 1956. The contract was actually for the CH-1A using the FSO-470 engine, however this engine had already been scrapped in favor of the FSO-526 so Cessna had to bite the bullet on the price and swallow the extra engineering costs associated with the CH-1B development which would become the YH-41.

The well used prototype, N5156, a CH-1A, was painted in an Army scheme and photos released showing this as the newly ordered Army YH-41 helicopter although it was really a "lipstick" job with the old engine. Pictures of N5156 in olive drab were used into1957 for advertising and promotional purposes linked to the military evaluation order.

By the end of 1955, the Cessna helicopter program had entered a transition from the preliminary design, prototype construction, test and certification phase to one of being integrated into the company as the beginning of the manufacturing phase thereby involving departments within Cessna that previously had no contact with the helicopter division. Charlie Seibel wrote a memo dated December 16, 1955 preparing the company for the manufacturing phase where he emphasized and explained the need for the strict tolerances and manufacturing techniques required for the helicopter's dynamic components. Metal fatigue considerations weren't of the prime importance on airplanes that the helicopter demanded. The cover memo for the report, "The State of the Helicopter," stated:"The Cessna Helicopter activities are now being integrated into the Pawnee Plant departments. Del Roskam and Chris Hesse have suggested that a discussion be prepared by the helicopter engineering department as an introduction to this new field. Accordingly, the attached report - "The State of the Helicopter" is submitted to you for your information.

"During the development period of the CH-1 helicopter, those of us in the Helicopter Division have been looking forward to this day when we start to build helicopters. We believe the sun is rising on a new business at Cessna. There will be many problems, and we are looking forward to working with you in solving these problems. Please feel free to visit with us at any time concerning our mutual interest, the Cessna CH-1 helicopter. (Signed) Charlie"

Putting the Army procurement contract in the proper chronological space, note that this December 1955 report, page 11, Section VIII, states: "The evaluation order of Cessna CH-1 helicopters is being purchased for one reason only. THESE HELICOPTERS ARE BEING PURCHASED TO EVALUATE THE AIRCRAFT, TO COMPARE OUR PRODUCT WITH OUR COMPETITORS LATEST PRODUCT, TO DETERMINE IF A PRODUCTION ORDER SHOULD BE MADE. Yes, these evaluation machines are sales tools for larger production. We can't wait to get QUALITY in the 100th helicopter produced. We must have quality in the first one, and in every one." Oddly, the actual Army contract for the YH-41 wasn't placed with Cessna until May, 1956, six months later.

This was a pretty tall order for Cessna where such techniques weren't necessary for the production of Skyhawks although the military production crews were well aware of material and tolerance controls as sub-contracted tail assemblies for the B-52 rolled off the line.

In May, 1955, Seibel addressed the American Helicopter Society in Washington, D.C., and stated that the CH-1 was, "the first helicopter I ever worked on where the performance exceeded my calculations." He was elected president of the society for the 1956-57 term. In conjunction with the AHS meeting, Newsweek magazine, May 2, 1955, ran an article on the CH-1; the article is reproduced below.

Another important, but non-engineering, event happened in the fall of 1955 as my son Douglas made his grand entry into this world.

Also of lasting importance, the first photos of the Bell XH-40 mockup were released toward the end of 1955, setting the stage for Hueys for many years to come.

Before going on with the YH-41 story, the ONR BLC project concluded in 1955 so will be briefly summerized.

The four-engine, pressurized Cessna Model 620 first flew on August 11, 1956 with Ralph Harmon at the controls. This attempt at a business transport was soon dropped in 1957 as it was apparent that there were too many surplus airplanes on the market for this approach to be a financial success. By all accounts, the airplane did fly nicely. As I remember, the fuselage was sold as scrap and became a house trailer.


1955 was a big year for the CH-1. Besides achieving cerrtification of the fastest and highest flying U.S. helicopter, landing on Pike's Peak and receiving an evaluation contract from the U.S. Army for the YH-41, the CH-1 also made the first flight tests of an active suction boundary layer control system designed to delay the onset of retreating blade stall, thereby meeting the objectives of the joint ONR and Army Transportation Corps contract originally signed in August, 1952 (according to Seibel, Cessna received the contract because a previous bidder backed out). Unfortunately no follow-on contract was obtained for this ground-breaking achievement. I don't know of any other helicopter flight tests ever being made, to this day, using an active, suction BLC system on the rotor blades, or any other form of BLC (see Kaman below) for that matter.

The 1952 Aircraft Year Book publication mentions the Cessna helicopter only in connection with the BLC program. In "The Industry" section, under the "Cessna Aircraft Co." heading, the following comment is made:

A long range Department of Navy research project is now in progress for design studies, experimental construction and flight tests on the Cessna helicopter.

The CH-1 flight on June 30, 1955 marked the first forward flight of a BLC equipped helicopter. The optimum airfoil configuration was established during our windtunnel tests in 1952/53 which included the rather unusual test mode incorporating oscillation of the blade section (pivoted on the quarter chord to simulate the actual change of angle of attack six times per second that the rotor blade encounters in flight). Both the rotor blade section 632015 and a NACA 0015 were tested with varying size and location of BLC slots and cyclically phased suction (less energy expended) was investigated.

Rotor blade test section with oscillation system in four-foot wind tunnel at the University of Wichita.

Above: NACA 0015 test section in wind tunnel, oscillating at 6 cps while suction BLC is applied cyclically. Note the unstalled tufts at 22 degrees angle of attack. Frame from high speed camera film. This model was an aluminum casting machined to a fine finish with an adjustable section for varying BLC slots. Below: Test section of NACA 632015 (CH-1 blade airfoil) at 22 degrees with BLC and with slot at 12.5%. Lift and pitching moment during oscillation were measured using pressure taps which fed a specially designed electrical airfoil pressure integrator. Confirming tests were later conducted in the ten-foor tunnel.

Interesting recent development: These tests of an oscillating airfoil were conducted over 60 years ago. A recent issue of Aviation Week (March 31, 2014) ran an article about Airbus Helicopters' experimental program using the Gurney Flap on a main rotor. Part of the program still to be conducted is a dynamic test on a two-dimensional airfoil. The article states:

Next will come 2-D dynamic tests, planned for year-end in a wind tunnel at Italian aerospaace research center CIRA. This scaled airfoil section model will oscillate in pitch at rates representative of a rotor blade in normal operation. The active Gurney flap will be deployed usisng the schedule and rates anticipated for the full-scale flight system.

Pressure tap integrator.

The suction pump for the flying system was a Cessna-designed rotary vane (six) type positive displacement pump driven at 1500 rpm by a Gilmer timing belt from the main drive shaft pulley incorporating a hydraulic clutch. Boundary layer air was sucked into the rotor blade through upper surface slots located on the outer section of the rotor blade ( a boundary layer fence was installed just inboard of the slots). These slots (located at 27.5% chord) were milled in the special blade section which also acted as the duct to direct air into a plenum chamber at the hub which also incorporated a cycling valve to operate suction only at that portion of the azimuth sweep (retreating side) where stall was likely to occur based on earlier testing using tufted blades with high speed photography. The air was then exhausted on the left side just aft of the cabin door. The rotor blade structural design and fatigue test was handled by the Prewitt Aircraft Company, Clifton Heights, PA, manufacturer of the Cessna blades. The photo below shows a test slotted blade section undergoing fatigue tests at Prewitt. The blades for the BLC program were specially constructed of an aluminum layered honeycomb sandwich (to replace the aluminum hat-sections and the .009 stainless steel skin) which was then bonded to the 4140 steel "D" tube spar to provide strength in the suction slot area and to provide a smooth air duct. An aluminum insert was provided at the suction slot area.

Richard H. "Dick" Prewitt had been the Chief Engineer at the Kellett Company and had designed the 1936 Army YG-1 Autogiro amongst other projects while working for Wallace Kellett. Army people called Prewitt "Daddy of this Whirligig." Prewitt eventually became a rotor blade manufacturer; the CH-1 blades were a brilliant design, incorporating a 4140 steel "D" spar with aluminum hat sections running aft to the trailing edge and then a thin stainless steel skin (excellent protection against corrosion and abrasion) was wrapped and bonded to form the exterior of the blade. Fatigue tests proved that the .009 skin would always show cracks before the load carrying "D" spar experienced any fatigue failure. Besides being an outstanding rotary wing engineer and pioneer in the field, Dick Prewitt was just a very nice guy and a real pleasure to work with.

The clean aerodynamic lines of the CH-1 and the high installed horsepower made the CH-1 a logical test vehicle for improving forward speed gains through the use of BLC. The CH-1 rotor blade airfoil section, 632015, had a mild, progressive stall but the NACA 0015 section proved to have better response to stall delay from BLC. Two sets of blades were constructed, a standard set and a BLC slotted set. Comparison tests were run with a standard CH-1 using the unslotted blades.

Final results showed an increase of about 13% in speed by delaying the stall, from 118 mph to 133 mph. Tests were conducted at 10,000 feet where blade stall becomes a speed limiting factor in many cases - the CH-1 was one of the few helicopters at the time that could operate effectively at altitude for these test conditions. Even with its altitude capability, control and power limitations kept the speed increase to this number; estimates are that a 50 m.p.h. increase would have been possible.

CH-1 boundary layer control test helicopter in-flight with chase plane. 42 hours of flight time were accumulated and 34 flights actually had the BLC system operating. Concurrently, Cessna had a contract for fixed-wing BLC testing on a Cessna 319A.

The photos below are taken from a 16mm Seibel film/video. The ground test system is shown, along with a view of the pump, and two views of the system installed in the CH-1. A high speed camera was used to record the action of tufts as seen in the bottom photo; note the boundary layer fence located at mid span.

The flight test engineer during this flying phase was Don Lodge who was my replacement when I went into the Army. Charles Harris was the technician. The system was not practical, however, in that the installed weight and horsepower required for the BLC system was entirely too much although no attempt was made to optimize inasmuch as the objectives of the contract were met.

This abbreviated discussion of the program only scratches the surface of this technical achievement. A complete report, "Application of Boundary Layer Control to Rotor Blades," by S.H. Hinton, Sr. Project Engineer, was printed in the April, 1957 issue, Vol. 2, No.2, of the Journal of the American Helicopter Society. It is also reported by Sz Fulop that the December 17, 1956 issue of Aviation Week has a 2-page write-up on the Cessna BLC program. Update 7/04: Thanks to Aviation Week Art Director, Bob McAuley, I now have a copy of the article - send CollectAir a SASE and I'll mail you a copy.

Several other attempts at BLC were made in this time frame by other companies although they involved blowing through aft facing slots on the upper surface of the blade. The small Monte-Copter Model 14 used a cold-cycle pressure jet powered by an air compressor in the fuselage; this arrangement allowed bleeding air through the blowing slots near the tips. Doubtful whether this not-too-successful ship ever flew with the blowing BLC. I was visiting the Piasecki Helicopter Company (a few months before the name was changed to Vertol - I think it was because Frank Piaseki had started a new company, Piasecki Aircraft) in October, 1955 and saw H-21 rotor blades in the Ardmore Plant No. 7 which were being prepared for BLC test stand operation; these blades had aft-facing blowing slots on the outer 50% of the span. The 1/8 inch slots were located at about 45% chord, 2 in. each in length with about 1/2 inch spacing. The blades had duct work with a spherical connection at the inner hub area to permit flapping and lead-lag. To my knowledge, these blades were never tested in flight and I have never seen a mention of this program in any publication. Sz Fulop has informed me that he found a brief article in the March 7, 1955 issue of Aviation Week which headlines "Piasecki Helicopter Corporation is conducting experiments on boundary layer control applied to blades of the H-21 Work Horse" though little else is said. The April 2, 1956 issue, in the Industry Observer section, states that Vertol has built a prototype of a H-21 rotor blade with boundary layer control and that it is at Wright Air Development Center for whirl testing. Also, the Aviation Week article mentions that Sikorsky "is also studying helicopter BLC". Perhaps someone can come up with more information.

Although it isn't boundaary layer control (BLC) as normally thought of, the Navy's Coanda Rotor Program (CCR) used circulation control to simulate changing blade pitch. The Kaman XH-2/CCR flew briefly in the late 1970s. The cutaway of the elliptical airfoil shape with trailing edge slots, shown below, had active boundary layer blowing to create a Coanda jet.

Display at NAS Patuxent River Navy Test Pilot School.


The CH-1B was certificated on July 5, 1957. The CH-1B was the basis for the YH-41.

The CH-1B/YH-41 evaluation quantity of ten machines, serial numbers 56-4236 through 56-4245, later designated as NH-41A in 1962, was manufactured at the Cessna Pawnee plant Commercial Aircraft Division with the first delivery, 56-4237, to Edwards Air Force Base for preliminary testing in September, 1957 following acceptance flying by Lt. A.E. Lush. An "army" of government inspectors from the CAA, Army and Air Force decended upon Cessna prior to delivery; in addition, the Army and Air Force Contract Technical Compliance Inspection Board, consisting of about a half-dozen colonels, met at Cessna to study the YH-41 design.

The helicopter was shipped to Edwards onboard a C-130; the YH-41 "Seneca" was loaded intact into the "Hercules" at McConnell AFB.

1963 Lockheed-Georgia ad for the "Hercules", six years after the YH-41 loading event!

The rest of the YH-41s were delivered to the U.S. Army Aviation Center for extensive user testing; the Transportation Supply and Maintenance Command to determine logistical support needs, and the Army Aviation School at Fort Rucker (two ships) for trainer suitability and service testing by the Army's Test Board. All deliveries took place in 1957 and 1958. Six "Senecas" were assigned to the Army by the end of 1957, the balance in early 1958.

YH-41 at Fort Rucker, Alabama. Seibel film/video.

YH-41A 56-4239.

Cessna built eleven CH-1B/YH-41 helicopters in total at the Pawnee plant, finishing production at the end of January, 1958. All jigs and fixtures were moved to the new Wallace plant along with helicopter engineering. The YH-41 Flight Handbook pictured above is dated 1 August 1957.

The Cessna brochure, shown above, carries photos, three-views, specifications and performance figures on all Cessna products from around 1958, including the 172, 175, 180, 182, Skylane, 310B, L-27A, T-37A, L-19E and the YH-41 Helicopter. The back cover invites you to "...try a drive in the sky!" The YH-41 page has a photo of 64237 and a three-view of the YH-41 (CH-1B) with cross sections. You can view and print out this page in PDF by clicking here.

YH-41 factory model displayed at the Kansas Air Museum in Wichita.

YH-41 factory model in the National Air & Space Museum collection when located on the 3rd floor of the NASM.

YH-41 model at the Udvar-Hazy Center. Note that this is really the CH-1A, not the CH-1B design used for the YH-41. CollectAir photo 2013.

Cessna factory model owned by Keven Smith.

Factory proposal model for Army. This model is the CH-1A, not the YH-41 (note stabilizer). The vertical "fin" for tail rotor is a bit too slim and the rotor hub is totally incorrect. Model from Allyson Vought collection.

The Edwards AFB test ship, 4237, was used for altitude testing at sites near Bishop, California. The YH-41 met performance figures at test sites ranging to 9,500 feet (Coyote Flats) and was flown by Air Force pilots with data gathering and maintenance by Edwards personnel. In late September, 1958, 4237, flown by Maj. R.G. (Bob) Ferry, made a dramatic rescue near Mt. Whitney. A man injured in a fall from a horse was picked up at an altitude of 9,300 feet and Ferry made a vertical takeoff from a 30 degree slope between tall pines. A news article stated, "He (Maj. Ferry) said the rescue mission could not have been accomplished without the exceptional high altitude performance of the YH-41 which permitted a vertical takeoff and climb from the high elevation of the rescue area."

The Cessna YH-41, 56-4237, tested at Edwards AFB.

Cessna YH-41 56-4238.

Cessna YH-41 at Edwards AFB in 1958.

The Army evaluation tests did not result in any further military contracts. The details of the Army's use of the YH-41 and reports (Project Nr AVN 3057)concerning the assessment of its utility for the Army are not really suitable (lengthy) for this article. If anyone can add personal information about the Army's operation I will be pleased to print the details. The 1995 book, Cessna Warbirds, by Walt Shiel has a lengthy section on the YH-41 including information on the Army's evaluation; more information on this book, and how to order it, can be found below in the "Afterword" section. Undoubtedly, the Army would have been reluctant to add another helicopter manufacturer to its contractor lists at the time, even with the YH-41's obvious performance advantages. Some comments published have indicated that the Army experienced problems with maintainability and there is no question that the CH-1B/YH-41 had stability and control deficiencies (detailed in the military reports) which were addressed later on the production CH-1C.

Painting by Cary Shiel entitled "YH-41 Seneca". 12" x 15" prints of this oil painting are available at Note that this is the CH-1A prototype, N5156 with the 470 engine.

The following extract from an appendix to the Army's official YH-41 report is from an article by Charles Siebel: "Captain R.G. Ferry (FTFOB) and Mr. V. K. Putnam (FTFEE) visited the Cessna Aircraft Company on 15-17 July 1958 to review progress on fixes being developed by this company for items deemed unsatisfactory on the YH-41 helicopter by Army and Air Force test agencies...

"Cessna personnel demonstrated fixes for every major problem area that has been found on the H-41....AFFTC personnel were highly impressed with this contractor's comprehensive and open-minded approach to the solution of these problems, and outstanding progress which has been made in a short period of time. This progress is commendable compared to past experience with other contractors in the rotory wing industry." The final military evaluation reports came out about two years later; by that time, turbine helicopters were on the horizon.

A "Check Test" of the commercial CH-1C version was made in 1959 by personnel of the US Army Aviation Board, US Army Aviation School and US Army Transportation Aircraft Test and Support Activity in the vicinity of Fort Rucker, Alabama. 57 hours of testing over a three week period were flown to evaluate correction of deficiencies noted in the YH-41 evaluation report, Project Nr AVN 3057. The CH-1C was maintained by Cessna personnel during the test period. In general, the test report stated that most of the YH-41 major deficiencies had been corrected but that there were characteristic and performance issues that precluded any further Army interest. In particular, the payload was insufficient, vibration was an issue (which should have been corrected by Cessna mechanics at the time), cyclic position in relation to the seat and anti-torque pedals was unsatisfactory and several other issues. The Army report, "Report of Test, Project Nr AVN 959 Check Test of the CH-1C (Modified YH-41) Helicopter," is available from CollectAir as a PDF file. If you would like to view this 7-page Army report, send CollectAir an email requesting that this file be emailed.

YH-41 during U.S. Army evaluation.

From the "Wichita Eagle", July 13, 1958.

From the "Wichita Eagle," August 10, 1958.

Some Army YH-41s were continued to be operated into the 1960s and some were either scrapped or repurchased by Cessna in the 1960s with the exception of 56-4244 which was retained as a museum piece. This machine is now in deep, dusty, poorly lighted storage at the U.S. Army Aviation Museum at Fort Rucker, Alabama. The pictures below appeared in the Mar/Apr 1977 issue of Aerophile in an article on the United States Army Aviation Museum, and the second photo appeared in the "Warbird Report" in the May 1979 issue of Air Classics. Note that this exhibit in the open changed drastically to dingy conditions at the museum by the time I took the pictures described in the next paragraph.

I took the photos of 56-4244 below in 1996 (compare to 1977 and 1979 pictures above). I know that 4236 (used for the instrument certification program) and 4245 were at Cessna in 1961 (they're in my logbook) so perhaps they both were bailed back to Cessna at the time for some test programs. As I recall, they were returned to the factory on flatbed rail cars and the engine mounts had been broken by the "g" forces of humping. Several references cite that six Senecas were purchased by Cessna from the Army to be rebuilt as CH-1C commercial models. The disposition of Army Senecas which were continued to be flown by the Army, other than the museum example, is unknown; they were probably scrapped.

The photos of 56-4244 shown below were taken recently by a visitor to the museum; a little less dusty than in 1996.

The United States Army Aviation Museum has a proposed expansion wing which would house and exhibit the experimental and prototype machines now in storage. The photos below show a model of the proposed building and a close-up of the YH-41 helicopter which would be part of the exhibit (a Hiller OH-5A is also included). Note the "layering" on the model's horizontal surfaces which suggests that 3-D printing was used. The photos were taken in June 2015.

The CH-1B (YH-41) was certificated with an unusual airspeed indicator; the redline maximum speed was adjustable, based on gross weight and altitude. This is the only instance for a helicopter that I'm aware of where the airspeed instrument markings (green arc and redline) can be adjusted in flight (mechanical as opposed to electronic). In addition, the CH-1B maximum airspeed (Vmax) chart had a discontinuity at 8,000 feet where the rotor minimum rpm was increased at that point (323 rpm to 343 rpm) resulting in the odd circumstance of the Vmax limitation increasing by 23 knots above 8,000. This resulted in the airspeed indicator having two adjustable verniers of altitude and gross weight, each having a distinctive color. The later civil production CH-1 version, the CH-1C, adopted a uniform minimum rpm with altitude and the instrument then had only a single adjustable scale.

RARE YH-41 ARTIFACT The production quantity of the airspeed indicator for the YH-41 would have been very limited based on two aircraft at the factory and the small evaluation quantity delivered to the Army in 1957/58. Shown below is one of those instruments, serial number 7 of Garwin's part number G1212A which is Cessna part number 1-332-147-1; unexplainably, this same Cessna part number was used for the CH-1C instrument with a different face. Also presented below is the Maximum Airspeed VS Altitude chart from the YH-41 Flight Handbook and an instrument marking diagram from the same source Note that this instrument is dated "July 9, 1957" which is within two days of the CH-1B certification date; the first YH-41 was delivered in September 1957. This is indeed a rare artifact from the YH-41; I would be interested in learning of any other parts which may exist in private hands.

Panel of YH-41 56-4244. Airspeed indicator at upper left.

The Cessna T-37 jet trainer for the USAF was operational in 1957 with production examples rolling out of the Prospect plant. The ad shown below is from the September 2, 1957 issue of Aviation Week.

The most interesting promotion of the YH-41 by Cessna and the Army occurred in December, 1957 as we set an absolute world's altitude record for helicopters with a modified CH-1B, ostensibly a YH-41 for publicity purposes. Details of this challenging record feat follow in the next section.

This photo of a CH-1B was taken by the well known photographer, Howard Levy, on May 29, 1957 at the Aviation Writers Association convention, McConnell Air Force Base. I show it because the ship has a color layout scheme that I don't recall seeing at the time. I guess the company threw on a new paintjob to impress the writers.


The high altitude capabilities of the CH-1 prompted Charlie Seibel, in 1957, to explore the possibility that a modified version of the ship could actually beat the existing absolute altitude record for helicopters. At that time, the three post-WWII record holders were turbine powered helicopters. First, the Sikorsky XH-39, using a Continental CAE Model 220 shaft turbine, flew to 24,500 feet in 1954, then the French Alouette II, piloted by Jean Boulet, with a record flight of 26,932 feet in June,1955 from the Buc airport which was soon beaten by a Sud-Aviation Djinn at 27,830 feet on March 22, 1957. Though not mentioned as a NAA record holder, a Piasecki YH-21 (reciprocating powered) went to a record altitude of 22,289 feet at the 1953 Dayton Air Show, piloted by USAF Captain Russell Dobyns, a remarkable feat.

Alouette II powered by Artouste IIB 400 h.p. turbine. From Republic Aviation Helicopter Division brochure, December 1957.

The idea that Cessna could beat these turbine records with a reciprocating engine was audacious, but Seibel was convinced. At stake was the potential of a military contract and Cessna was going all out to gain approval for the new helicopter on the block.

The concept was to put a record winning ship in the air with an Army pilot at the controls for the record attempt and then promote the heck out of the achivement, touting it as an Army record in a Cessna helicopter. That is exactly what we did.

Work on the record machine began with my Test Proposal No. 18, "Altitude Record Attempt", issued on September 20, 1957, the same month that the first YH-41 was delivered to Edwards AFB. The introduction to this proposal read as follows: "An attempt is to be made to establish an altitude record with a specially equipped CH-1B helicopter. Major modifications to the aircraft in preparation for the record attempt will be:

"(1) Engine modifications to include higher supercharger blower ratio and installation of altitude magnetos and high tension leads.

"(2) Removal of all unnecessary equipment to reduce the empty weight of the helicopter."

The proposal also stated, "Two flights will be made. The first flight will be a preliminary attempt to determine if the altitude record can be broken. Data will be taken with a gun camera during this flight. If satisfactory results are obtained on the first flight an official record attempt will be made with the cooperation of the NAA."

This effort had been preceeded by a preliminary altitude flight on July 2, 1957 in N5157 (ship #3) which was not extensively modified but somewhat lightened by removal of seats, engine cowl, upholstery, L.H. controls etc. for a T.O. gross weight of 2421 lbs. which included a single pilot and 20 lb. of ballast. An altitude of 23,100 feet was attained with the standard engine; Jack Zimmerman was the test pilot. Extrapolating this test data for a further weight reduction and using a power chart for a higher blower gear ratio engine, it was concluded that a record could possibly be set thereby setting in motion the proposal of September 20th.

The helicopter was stripped of nearly everything that wasn't essential for flight or pilot safety. Some examples: Most of the electrical system, batteries, relays, generator etc. were replaced with two dry cells to operate instruments. The auxiliary fuel pump was eliminated. The starter relay, vibrator, and the starter itself were removed after starting. The entire landing gear was replaced with two small scuff tubes on belly. The exhaust system was removed and only short pipes remained. Doors were replaced with vinyl with a zipper emergency exit on rh side. The transmission oil cooler was removed. The engine fan was lightened with removal of the fan ring and dome. Engine filter, air box and CAH removed along with miscellaneous baffles etc. All this change required tail ballast which consisted of a lead weight mounted on a braced tail skid; the F-1 oxygen tank was also installed on the tail skid for ballast. The final configuration had to be flown off of a special dolly. Approximately 266 lbs were removed with about 27 lb. added including ballast. I was assisted on this project by two other flight test engineers, Frank Robinson (yes, the helicopter entrepreneur who now builds more nifty helicopters than the rest of the industry) and John Parks; we were all under the age of 27.

Ship #3 was prepared for an instrumented test flight on December 18, 1957 with Jack Zimmerman at the controls - see photo below for color photo of this flight at takeoff.

Ship #3 December 18, 1957 on test flight. Seibel film/video.

The special Continental FSO-526-2X engine was installed and most weight control items removed with the exception of the landing gear which was retained for this flight. Fuel load was a full 59.2 gallons for a takeoff gross weight of 2408 lbs. Jack flew the prepared flight profile and reached an altitude of 26,860 feet with 42 gallons of fuel remaining in the tanks. It should be mentioned that the decision had been made to terminate the final altitude attempt with the Army pilot when the onboard fuel reached ten gallons. Prevailing winds caused the ship to head east and Jack landed in Augusta, Kansas, about 18 nautical miles. Following his return flight from Augusta, there were 32 gallons of fuel remaining. With this information, we were certain that the record could be broken and arrangements were made for an Army pilot and NAA certification of the record flights.

The altitude record flights were made on December 27, 1957. Captain James E, Bowman, U.S. Army Aviation Board, Fort Rucker, Alabama was the pilot for the record attempts; he was the evaluation pilot for the YH-41 at the Test Board. Two flights were made in order to qualify for two weight categories. The helicopter was weighed with the NAA representative in attendance, M.J. (Jerry) Gordon from Beech Aircraft, who witnessed the figures. The T.O. weight for Flight #1 was 2108.7 lbs which included a reduced fuel load and a recording barograph. This flight qualified for the 1,102-2,204 lbs category. A beautiful winter day between Christmas and New Year's; the record flight went off without incident. Captain Bowman flew the profile, narrowly squeezed in airspeed where the best rate of climb speed can also be limited by compressibility and retreating blade stall at the high angle of attack required. Reaching an indicated altitude of 30,355 feet, Bowman returned to the Wichita airport now known as Wichita Mid Continent. The photo below is one of the only existing photographs of this record breaking ship, taken as Captain Bowman returned from Flight #1 and landed on the dolly. The second photo shows it hovering several feet above the dolly.

This photograph was marked "Not for Release" and neither the public, the Army, nor the press was aware of what this modified ship looked like; Captain Bowman later had his picture taken for publicity with a standard YH-41 in the background giving the impression that the record flight was in that helicopter. This publication of this photo of N5157 is the first time to my knowledge that the photo has been shown outside of Cessna except for a video made by Charles Seibel in 1990 which shows a hovering scene (still) as Bowman made his landing (see photo below). A second record attempt was made with a takeoff gross weight of 2229.1 lbs. by adding about 20 gallons of fuel; this qualified for the 2,204-3,858 lb. category in which there was no previous record. Bowman reached an altitude of 28,200 feet on this flight. Of special interest is the fact that the CH-1 left a contrail! Caught in the edge of the jetstream, Bowman was carried east and had to land at El Dorado, about 31 nautical miles from takeoff. He caught the wrath of the airport manager as he landed on the tarmac and burned holes in the asphalt with the abbreviated straight exhaust pipes!

Photo from Seibel film/video.

No still photos were taken of the ship in forward flight or at altitude. I did the painting below (alkyd) to show this barebones helicopter at 30,000 feet laying down a contrail, a common sight over Kansas prairies , but not by helicopters. I titled this scene as "No Place for a Helicopter."

CH-1B setting world's altitude record - "No Place for a Helicopter".

The press release on this record flight featured Bowman's picture with a YH-41 as shown here in a newspaper clipping. This picture was taken by Bill Webster from the Cessna Wallace Plant and was picked up by the wire services and widely distributed.

Captain Bowman was presented the Distinguished Flying Cross by General Maxwell Taylor in Washington, D.C. on January 2, 1958. The same day, Bowman appeared as a guest on the Arthur Godfrey show and gave an account of his altitude feat. If I remember correctly, Captain Bowman was seriously burned in in a crash of an Army L-23 in St. Louis some time later.

Previous to the Cessna record flight, Captain Bowman participated in several record flights in the Piasecki CH-21C, tail number 55-4150, in 1956 while he was also with the Army Aviation Test Board 6 at Fort Rucker. Bowman was one of the three pilots who established the first non-stop coast-to-coast flight by a helicopter, being refueled in flight or in hover by ground personnel. Prior to the cross country flight, Bowman, along with Joseph Givens, broke the closed-circuit sustained flight record with a 30-hour endurance stint, along with other record flights in the CH-21C. The photo below is from the book, The Piasecki H-21 Helicopter, by Robert Brandt and William Davies; Captain Bowman is the sixth man from the left.

CH-21C, "Amblin Annie," on the non-stop, coast-to-coast flight. Shown being refueled from a U1A Otter. Photo courtesy of USAAM Museum Fort Rucker.

Capt. Bowman was featured on the cover of the January 24, 1958 issue of the Cessna news, Cessquire. You can view this employees newsletter by clicking here.

The final official NAA (acting as the U.S. representative for Federation Aeronautique Internationale) altitude figure was given to Cessna as 29,777 feet as measured by their sealed recording barograph, a device with a rotating drum, lamp blacked surface and a barograph needle scribing a mark. I did not agree with this lower figure inasmuch as we had established an altimeter error of less than 29 feet at the altitude and airspeed attained. As expected, our absolute world's altitude record was beaten the following year, again by a turbine powered Sud Aviation Alouette II flying from the French Air Force test center at Bretigny, near Paris; an altitude of 36,501 feet was reached. Turbine helicopters dominated the altitude records during the 1950s with the single exception of the Cessna. In December,1959, Capt. Walter J. Hodgson and Maj. William J. Davis USAF flew a standard Kaman H-43B with a Lycoming T-53-L-1B engine to an altitude of 30,100 feet at Bloomfield, Connecticut, an unofficial record for Class E-1-D Helicopter.

Records are only set to be beat. It's exciting to be able to do something "first" but the realization is that constant development results in "records" becoming commonplace as time goes by, so while no other helicopter/pilot had ever been to 30,000 feet when we set a record, the world of turbine helicopters changed everything. Standard military versions of working helicopters left the 30,000 foot mark far behind. In 1964, a group of pilots from the Army Test and Evaluation Command's Edwards AFB and the Fort Rucker Test Board set a new record for weights up to 9,921 lbs. in a Bell UH-1D Huey by reaching 35,150 feet. The absolute altitude record for heliopters (E-1) without payload was set by a French SA 315 Lama, piloted by Jean Boulet, on June 21, 1972; the Lama attained an altitude of 12,442 m (40,814 ft.). A model of the SA 315 is shown below; more on this model can be viewed on the Helicopter Display Model Annex page. Update: Jean Boulet died on February 15, 2011 at the age of 90.

Prewitt Aircraft Company ad from the AHS Newsletter of May, 1958; shown is one of the jigs used to mold the CH-1 rotor blade.

The YH-41 was modeled in 1:40 scale in 1958 by Adams Action Models. Although the YH-41 configuration was reasonably accurate, Adams elected to add a popular new missile to the model which resulted in a ridiculous installation. To Adams credit, the building instruction sheet included information on Capt. Bowman's record flight; this section is shown below. The molds for the Adams kit were later purchased by Life-Like and the instruction sheet omitted reference to Cessna or Capt. Bowman (more details on these kits are covered later in this article).


The Helicopter Division began a concentrated effort in 1958 to further refine the CH-1 by addressing various flight stability and control deficiencies (from military evaluation), exhaust problems, a new tail rotor and raising the gross weight by 100 lbs. Additionally, the U.S. Navy and the U.S. Army were seeking a new helicopter instrument trainer and the CH-1 was, in our view, the perfect ship for the job, if and when we could engineer sufficient changes to meet instrument flight requirements. This ongoing department effort resulted in the Cessna CH-1C Skyhook which eventually became the civilian production version with initial deliveries in July 1961. An instrument variant of the CH-1C, equipped with additional stability devices, was licensed by the FAA for instrument flight, making it the very first helicopter to ever receive IFR certification and the only one, to this day, to be qualified for instrument flight without an autopilot installation or the need for electronic stabilization. The instrument program was aimed solely at a military contract as there was no real market for a light, civilian instrument rated helicopter. Unfortunately, the Navy elected to purchase the Bell HTL-7 (Bell 47K) for instrument training and took delivery of 18 ships in 1958. The Bell HUL-1 was already in Navy inventory. However, an Army need for instrument trainers was still in the works.

Navy Bell HUL-1.

Pre-production CH-1C paint scheme - 1959.

The CH-1B's poor lateral stability and unwanted roll inputs caused by the combination of power changes with the high tail rotor position was the prime deficiency to be taken aim at. Seibel and the design department under project engineers Mel Vague and Bob Smith, with design engineer Harold Bull and others, came up with a mechanical roll rate gyro which was driven off the main transmission; the nearly 4-lb., 10 in. single-axis gyro's inputs were fed into the lateral boost system through mixing linkage to effect significant damping of roll excursions.

March 1960 advertisement.

To correct the tail rotor thrust rolling moment, a mechanical feedback from a cylinder sensing the pressure differential across the engine supercharger fed into the lateral boost valve through a mixing linkage; this lateral cyclic pitch input counteracted the rolling moment from the high tail rotor thrust line very effectively. Longitudinal stabilty was improved by use of a larger, 9-ft. span stabilizer which was free floating in hover to a vertical position caused by the downwash. The stabilizer was rotated about its pitch axis in response to forward speed by a ram air pressured bellows linked to the stabilizer torque tube (spar). At about 40-50 mph the stabilizer reached a stop which, in turn, was linked to the collective pitch. A drop in collective pitch, such as entry to autorotation or a change in power moved the stabilizer stop and permitted the stab to change incidence to achieve longitudinal trim. The ram air bellows damped the stabilizer response during the transistion stage.

CH-1C image from Cessna 16" x 20" color promotional litho - 1959.

A true color view of the 1959 CH-1C as photographed for the color promotional litho. The litho copy that I have is faded.

The CH-1C received FAA Type Certificate approval on July 28, 1959, the "Airplane Flight Manual" being signed by FAA engineering test pilot Harold H. Hermes (1920-1989) from the Kansas City regional office. Hermes was a Wright Field Army Lieutenant in 1943 and was a pilot on the Army team that demonstrated landings and Takeoffs in a Sikorsky XR-4 off a deck platform in the open ocean on the freighter James Parker, a first. Hermes had been a helicopter student, along with Charles Lindbergh, of Charles Lester Morris who was Sikorsky's chief helicopter test pilot from 1941 to 1944. This helicopter was further modified with flight instrumentation sufficient for instrument flight although the helicopter was not certificated for actual instrument operation. The combination of dual instrumentation and the excellent handling qualities and stability made the CH-1C a delight to fly on instruments. This ship, N5159, was taken on a demonstration tour of eastern military installations (mostly Washington D.C. and Fort Rucker) in 1959 to show off the instrument capabilities to the military with an eye to the Army's instrument trainer needs. J.J. Pohlen from Cessna and a contract pilot, Hersey Young from Denver, flew the demonstration circuit. At this point the CH-1C was not FAA certificated yet for actual instrument operation. The booklet shown at left is from 1959 and was used during the tour. In it, the CH-1C is referred to as the "CH-1C Instrument Helicopter". The Cessna photo below, from 1959, of the helicopter in the clouds was to subtly infer instrument operation (and quite effectively). Army pilots were impressed with the CH-1C's instrument capability and were satisfied with it "as is".

This photo was featured in "The Aerospace Year Book 1960". In my opinion, this is the finest photo ever taken of the CH-1. Cessna used this photo in a full-page ad in the Dallas-based magazine, "Flight," in December, 1959.

As an aside, by March, 1959, in the six years since the Cessna 310 made that first flight on a cold winter day in January, the factory turned out 1,000 310s.

The Cessna helicopter was featured on the cover of the "American Helicopter Society Newsletter" many times. This example is from December, 1960. A thorough nine-page article on the new CH-1C Skyhook was included in this issue; the article was written by Oliver Hopkins, Rotary Wing Specialist, who later died in a crash of a Skyhook while flying cross country on a demonstration tour - more info on this further below.

As 1960 approached, several projects were underway. An improved exhaust system was devised to prevent hot gases from burning grass and combustibles. No doubt that my hearing deficiencies today are the result of doing test work on that damn exhaust system! The decision to go into production hadn't been made yet and engineering was "cleaning up" the CH-1C to prepare for civilian sales. The potential of military buy of the CH-1C as an instrument trainer spurred action on that front in two directions. Although the basic CH-1C as certificated seemed to be an ideal instrument platform, the helicopter did not satisfy the FAA requirements for instrument flight. Since there were no regulations directly aimed at helicopter instrument certification (we were the first to ever apply), the FAA, in their usual wisdom, elected to apply airplane requirements with some special regulations thrown in. Therefore we had to meet dihedral stability criteria, stick force gradiant with airspeed criteria, etc.

We went to work and devised mechanical systems to satisfy the FAA regulations. Ram air sensors were used to drive bellows which fed the proper stick force gradiants for both longitudinal and lateral controls: the longitudinal bellows was equipped with a "g" valve which phased the input correctly. The lateral bellows (2) were fed by a vertical cylinder on top of the cabin which had ports located 90 degrees apart, sensing yaw differential pressure - the cylinder could be rotated for yaw trim. The lateral bellows were also fitted with a "g" valve (located in the aft portion of the tail cone) to provide proper phasing (bellow force input alone would be destabilizing). Fuselage strakes atop the cabin satisfied dihedral stabilty requirements. In all, the instrument version finally met all the FAA regulations by mechanical means alone, no black boxes, no electronic gadgets. The final product did not fly as nicely as the basic CH-1C! You could, however, fly the ship hands off indefinitely and regulations were met. After going many rounds with the FAA, the modified CH-1C ( a loaned YH-41 brought up to the "C" configuration, Army 64236) was finally approved for instrument flight (two pilots) by the FAA Kansas City Regional Office on July 7, 1960, the first helicopter to achieve this certification. The two photos below pertain to the IFR award. Note that this was the only CH-1C that was built to this configuration.

Caption from The Wichita Beacon, October 2, 1960: "Cessna Aircraft Co. and Federal Aviation Agency personnel who took part in certification of Cessna CH-1C as the first instrument flight approved helicopter are (left to right) Charles Seibel, Cessna helicopter chief engineer; Steve Remington, Cessna flight test engineer; Jack Zimmerman, chief test pilot for Cessna; Harvey Van Wyen, Kansas City FAA flight test engineer; Bob Faith, Washington, FAA flight test section; Hal Hermes, Kansas City FAA flight test section chief, and Clay Staples, of the Washington FAA flight test section."

IFR test ship 64236 and panel. Seibel film/video.

Instrument ship 64236 at Wallace Plant.

Also in October, 1960, the CH-1C was "unveiled" with an official public introduction at the Municipal Airport and an announcement that the helicopter was to be put into production for civilian sales with the first deliveries scheduled in mid-1961. Cessna sales pilot J.J. Pohlen gave dignitaries and press people rides. By December, 1960, over 70 Skyhook demonstrations were given to various operators and government agencies. The Prospect Plant Department 146 commenced production of the Skyhook. The Skyhook was to be marketed through Cessna airplane dealers for sales and servicing, a rather ambitious undertaking as the helicopter was an unfamiliar product for most dealerships. Ships were being constructed in 1960 with serial number 15 on the line by October.

Cessna CH-1C, August/September 1960. This unpublished photo was taken by flight test engineer John Parks at the Cessna Wallace plant. The production color scheme was basically the same with the exception that the logo "CESSNA" was much larger on the production versions. This appears to be ship N5749 in which I received much of my helicopter flight instruction from Jack Zimmerman.

Meanwhile in 1960, military sales of the instrument CH-1C were being pursued. Ship N5159 (a standard CH-1C) was flown to the Patuxent River Naval Air Test Center in May, 1960. Test pilot Jack Zimmerman and I, and a Cessna Technician conducted a structural and aerodynamic demonstration of the CH-1C in accordance with an abbreviated form of SR-189, Section 6, to furnish only enough data for a basic flight envelope sufficient for a Navy evaluation of the ship. Patuxent engineers, including Richard Wernecke, installed instrumentation and witnessed the tests which included "g" maneuvers, static stability, height-velocity curve autorotation landings with a Fairchild photographic flight analyzer, a 7.0 fps hard landing measured with a Trodi, and many other maneuvers. It was concluded that the CH-1C met structural requirements for Navy testing of performance and stability.

Official U.S. Navy photograph of the Cessna instrument panel; back of photo is stamped "U.S. Naval Air Station Patuxent River. MD."

Engine to Transmission drive shaft. The diameter was based on torsional stiffness requirements. U.S. Navy photograph.

Reference Cessna Report 1-941-144. Yet, the CH-1C lost out to the Bell HTL-7 for an 18 ship Navy buy for instrument trainers in 1960, even considering that the CH-1C was the only helicopter to have been FAA licensed for instrument flight - there was no way that the Bell Ranger could have met civil IFR requirements. This was standard practise however as military helicopter instrument training was all conducted in helicopters that couldn't meet civil standards as the CH-1C did.

CH-1C over Wichita in nearly the production paint scheme.

Earlier paint scheme for the CH-1C.

Other projects and CH-1C refinements were also being pursued in 1960. Design work on a new, fully coning tail rotor commenced; this improved tail rotor would be test flown the following year but, to my knowledge, was not incorporated on the production line machines. The Army RFP for the huge Light Observation Helicopter (LOH) program had many companies working feverishly on design proposals including Cessna. I was working hot and heavy on the "Performance Data Report", and other design features, for the Cessna CH-4 Design Proposal in the fall of 1960 and the full-scale mock-up was going together late in the year. The proposal had to be ready for submittal by January 16, 1961.

Consider this: by the end of this year, Cessna had been investing in the development of the CH-1 helicopter for eight and one-half years with very little return (delivery of ten ships to the Army and a small ONR contract). The company was betting on landing the LOH contract, a huge program, getting some military orders for a CH-1C instrument trainer, and getting a significant foothold in the civilian helicopter market with the Skyhook. This was the position of the Helicopter Division as the new year of 1961 dawned.

March 1960 advertisement.

The above view of the main Cessna aircraft plants is from a brochure printed around 1958/59. The top plant is the main Pawnee Plant comprising the Commercial Division. The Helicopter Division started in this plant in 1952; the engineering office was located at the very corner of the main production building, overlooking the factory runway - center near top of this photo. The helicopter engineering activity was then moved to the Prospect Plant (Military Division), bottom photo. You can see the helicopter runup and test pad in the very center top portion of the photo. Eventually the Helicopter Engineering and Test departments moved to the new Wallace Plant (Military Division)around 1957 (center photo) - ground breaking for the Wallace facility began in 1956.

A small anecdote to add to this anecdotal history - a snippet of Charlie Seibel's playfulness. Our Helicopter Engineering Department moved and shared floor space at the new Wallace Plant; lighting was excellent with fluorescent tubes behind rippled plastic panels in the ceiling. One day Charlie came into the office sporting this toy helicopter which was powered by a spooled cord. The type of toy is pictured above - actually a very nice helicopter that climbs with authority when spun; as the rpm lowers, the weighted blades rotate about the pitch axis to a lower pitch and it autorotates to the ground. The blades are quite substantial and the climb rate depends solely on how hard the cord is pulled. Charlie proceeded to show us how well this device would fly and, in his exuberance, he gave the cord a mighty tug. The helicopter made a rapid ascent and chewed up the plastic ceiling before autorotating with a crash. A good laugh was had by all in witness to this ill-fated test flight.


We're now coming to my last year of involvement with the Cessna CH-1.

The CH-4 LOH proposal was submitted in full to the Army in January, 1961 to kick off the year. An award announcement was expected by May, 1961. Companies submitting proposals were Bell, Hiller, Boeing, Cessna, Gyrodyne, Kaiser, Kaman, McDonnell, Republic, Hughes, Lockheed and Sikorsky; a dozen contenders for two spots. The CH-4 mock-up is pictured below; the turbine engine compartment is located behind the rear seats.

Flight strain survey tests and performance tests on the new coning tail rotor took place during the first half of the year. Talk continued about Navy and Army interest in instrument trainers and the Navy indicated some interest in a turbine powered CH-1 using the Boeing engine.

Also of particular satisfaction for myself, I started to receive flight instruction in the CH-1C from Jack Zimmerman in January, 1961 and received dual in N5749, and Army ships 56-4236 and 4245.

The Winter 1960-61 issue of the "Cessna Pennant", a promo company magazine, featured the Skyhook on the cover. This quarterly publication, shown below, was the very first, Vol. 1 No. 1, and was published, "to keep its readers informed of Cessna developments, activities and progress." Ship N5747 is featured on cover.

Military contracts for Cessna helicopters were not to be in 1961. The LOH award went to Bell and Hiller in May, quite a blow to Cessna hopes for entry into large-scale military production. The Navy BuWeps were looking for an assault support helicopter for the Marines and the Army LOH designs did not satisfy their requirements, so bids for a for a new ASH helicopter were solicited from ten manufacturers, including Cessna, on October 16, 1961. Cessna, Gyrodyne and Doman did not respond. One item of LOH interest. The Hiller proposal for the LOH, as submitted to the Army, included a design philosophy report which outlined the Hiller design process for their proposal. A number of wind tunnel models of differing fuselage configurations were tested for drag. As part of the study, the report states, "...the Cessna YH-41 was studied as a representative high-speed helicopter. The models were built to gather wind tunnel data which could be compared with predicted performance figures..." The YH-41 wind tunnel model, as built and tested by Hiller, is pictured at left (from Hiller Engineering Report No. 60-101).

Production was in full swing at the Prospect plant on the Skyhook with an announced price of $79,960 and ships coming down the line in May, 1961. A fatal Skyhook accident took the life of Marketing Division pilot, Oliver Hopkins, near Midland, Texas in April. He was on a demonstration tour of the CH-1C. Hopkins was one of the airplane sales specialists who got a helicopter rating. I don't know what the final NTSB report found but, at the time, it was reported that an eyewitness, working on a powerline, saw the rotor chop off the tailboom. I assumed it was a power failure and the collective was not lowered in time to prevent rpm decay. The Cessna policy of not hiring helicopter pilots for sales work may have bitten them. The following first-hand account of the circumstances surrounding the crash of Hopkins' helicopter was written and submitted to CollectAir by correspondent Richard Post in November 2010. I can't verify the NTSB findings.

I found your site quite by accident. I had searched for models of the Winnie Mae for my six year old grandson, Wiley Post, a great great nephew of the original. He is a Snaptite and Lagos builder and loves airplanes. What caught my eye was the interesting article about the Cessna helicopter. I was a kid working on the flight line and in the office at Midland Air Park at the time of the fatal crash. The pilot had landed there to refuel enroute from Austin ( where he had given demo rides to the head of the Texas Highway Patrol and others) to El Paso. Whilst the helicopter was being refueled, the friendly pilot chatted with me and a professional pilot in the waiting room. He talked about the chopper and his demo tour. He apologized for not giving the both of us a quick hop but said he was in a time press to get to El Paso before dark. The wind always blows in West Texas and you could take our local wind gauge and add 20 mph to our figure for the wind in the "mountain" pass he would encounter enroute to El Paso. The professional pilot suggested he head northwest toward New Mexico ( Hobbs, I think.) He could refuel there if necessary and then swing back down to his destination and avoid the high winds in the pass and get to ELP before dark. That is what he decided to do. He said goodby and left. About 15 minutes after he left, I got a call from the police inquiring about the helicopter. A telephone lineman working on a pole watched the chopper fly over, saw the tail rotor come off and watched the chopper dive nose first into a plowed field and burn. The lineman immediately called the police. I immediately drove to the scene and was able to identify enough of the helicopter and gave some information to the police. I quickly returned to the office and took a phone call from two Cessna pilots who were flying a C-210 chase plane for the chopper and had landed at the Cessna dealer at the other Midland Airport about 15-20 miles further to the west. They had been trying to locate the chopper and had just learned of a probable crash. The next day the FAA and the chase pilots came by to interview me. I was able to clarify the confusion about why the pilot was heading northwest instead of west and confirm the pilot"s cheerful demeanor. Sometime after the crash, we were all told that the crash was caused when a sealed shaft running to the tail rotor snapped and chopped off the tail rotor. The resultant nose heavy helicopter plunged nose first to the ground. The shaft was lubricated and sealed and supposed to have a very much longer maintenance life, which gave considerable cost savings. After the crash, no one in Texas wanted to take a ride in the Cessna helicopter and the East and West sales tours were canceled. ( As we were told.) Obviously I will never forget this story and you may find some interest in the story also. I will be back to see more of you site.
Regards, Richard Post.

The first three production CH-1Cs in work at the Cessna Prospect plant, Spring 1961.

We had no serious accidents doing test work during the life of the program. One typical incident: Jack and I were doing a strain survey on the new coning tail rotor. Reversal maneuvers were required which entailed full travel tail rotor pedal reversals at the never-exceed-speed. Working up to it, we were trying the reversals with both left pedal first and with right pedal first. We managed to clobber the tailboom fin with a blade but everything stayed together so we flew back to the field, a flight of about ten minutes. Oddly, the same thing happened when I later worked at Hiller Helicopters as we struck the tail boom (and battery box) during left pedal first reversals at Vne on the UH-12L4, #2173, in 1964.

My recall is a bit sketchy, but around 1960-61 an Army YH-41 crashed in a steel yard in Albuquerque, New Mexico, killing the pilot and a female civilian who, most likely, was an unapproved passenger. I and a technician, Mel Osborne, drove all night in a VW to Albuquerque to investigate the wreckage. My brain must have fried in the 116 degree heat because I just can't remember much of it but I must have written a report. I received (7/03) comments from Bill Evans of Phoenix who remembers, as a young teenager, the Arizona Republic newspaper carried a front-page photo of the crashed YH-41 in an Albuquerque steelyard along with information that the Army pilot had met a flight attendant in a bar and decided to demonstrate the YH-41, crashing soon after takeoff.

The May, 1961 "Flying" magazine carried a significant pilot report on the Skyhook; this article was well timed to be just prior to first deliveries scheduled for June/July of the 1962 Skyhook. A CH-1C was featured at the Cessna Dealers All-Model Show at the famous Nut Tree Inn in June, 1961. Deliveries of new Skyhooks to dealers and distrubutors began in the fall of 1961.

Production CH-1C. Photo courtesy of Gary Cheatum via Bob Smith.

Examples of advertising that appeared in the first half of 1961.

The Helicopter Experimental Department 182, under Dick Ledwin, constructed a cut-away of the Skyhook for the training section ground school of the Marketing division in the summer of 1961. Dick is pictured below on the right as he shows the dynamic components and internal working parts of the CH-1C.

Cessna sold about fifteen (according to Charles Seibel in a 1991 video presentation) CH-1Cs to the U.S. Government, designated as UH-41As, under the U.S. Army Transportation Material Command, for use in the Military Assistance Program (MAP) or the Mutual Defense Assistance Pact (MDAP). Serial numbers were 62-5845/5848, 62-12350, 63-9793 and 63-8067/8071 (these s/n's add up to only 11 so were there more?). Of interest, some of the MAP helicopters were delivered by Cessna in 1963, well after the decision to scrap the commercial program was made. These ships went to Latin American or South American air forces and Iran and used primarily as high altitude rescue and casualty evacuation aircraft as pictured at left. No information seems to exist which documents the final disposal of these machines. Were they eventually returned to the U.S. Army for scrapping? - doubtful. Do some still exist? - perhaps. Any wrecks still in some overgown jungle hideaway? If you can shed any light on them please let me know. With six helicopters delivered to the Ecuadorian Air Force, who knows, maybe there is a Cessna helicopter hulk on some schoolyard playgound in Guayaquil or on some slope high in the Ecuadorean Andes! Max Sonnenberg, an operator of one of the first CH-1Cs, was in Equador near this time frame and he says that the Equadoreans never used the ships because they didn't know how to fly or maintain them. However, the photo below shows an Ecuadorian Cessna in service with the Escuadron de Rescate y Salvamento 2113; The Grupo de Combate 221 received six Cessna H-41A Senecas at Guyaquil in mid 1962.

Some ships (five initially) were operated in Iran as well. Bob Smith remembers spares manager Kenny Burris shipping a rotor blade to Iran in the early 1960s to replace a badly dented blade which had made contact with an unfortunate person's head. Ed MacKenzie recalls performing production test acceptance flights on two MDAP Skyhooks destined for Peru in 1962 - he also trained several Peruvian pilots. According to Seibel's 1991 video, some of the South American MAP ships were diverted to Iran.

Mr. Farzin Nadimi of Tehran, Iran has added (November 2003) some valuable information to the subject of Skyhooks in Iran. Mr. Nadimi is an aviation historian and has interest in the Cessna program. He writes, "Some time between 1962 or 1963 (Persian year of 1341), the Iranian Gendarmerie Aviation Unit received three Cessna UH-41A helicopters for observation, liason and utility purposes. Flying and maintenance crew were reportedly trained at the Lackland Army Aviation base (correct me if I'm wrong). Service of these helicopters were unique not only in Iran, but also the region. They were later replaced by Augusta-Bell 205 and 206 models, and no further information is available of their final fate." Mr. Nadimi has run across internet info which suggests that five ships, serial numbers 63-8067/8071, were destined for Iran under the MAP program. He has submitted two photos, shown below, of the Skyhook in Iranian service. It is interesting that the Skyhooks were replaced by Augusta-Bell turbine helicopters which would have been years after the Cessna buy-back of Skyhooks and the Army discarding the YH-41s - perhaps there is a junk CH-1 lurking somewhere in Iran serving as a chicken coop. Mr. Davood Moazami of Tehran, Iran, an aviation researcher, emailed information in December 2006 stating that there were five UH-41s delivered to Iran. He says that three helicopters crashed and two were retired because of low performance in Iran's mountains, but no dates were given.

Information from Iran indicates that the very first helicopters to be introduced in Iran were Westland Whirlwind Series 2 (no. 4-301) in 1959 which were acquired by the ministry of interior for use in ferrying officials around the country; the pilots were British. The Whirlwind was a British version of the Sikorsky S-55/H-19.

UH-41A in Imperial Iranian Gendarmerie Aviation service.

The pilot on the left is Lt. Ravravan. He was the very first Iranian helicopter pilot and is currently living in Iran.

Correction and update: Issue Number 10 of the The Aviation Historian has an extensive article on the Iranian Skyhooks which was written by Colonel Gholam-Reza Rahbariyan who was Iran's first rotary-wing pilot. Many photos are included in the article including the photo above . The pilot's identification of Lt. Ravravan in the caption above is in error as it should be Rahbariyan. Refer to the TAH10 article for an accurate, first-hand account of the Iranian MAP program.

The photos below are from the Seibel film/video and were taken in Iran by Robert Pemberton. Shown is one of the MAP helicopters being unloaded from its shipping container and later operational in the field.

Correspondent Sid Nanson kindly provided some additional research on the MAP helicopters, confirming the serial numbers of the Ecuadorian ships and the Iranian ships which were 63-8067/8071. The six helicopters in Ecuador flew a total of 849 hours between the first delivery in June 1962 and September 1964 when they were classed as inactive. Three UH-41As were lost to operational accidents. The remaining three Ecuadorian Air Force ships were transferred to Iran in early 1965.

On February 28, 1961, Bill Thompson, chief engineering test pilot, made the first flight of the twin-engine Skymaster, fixed gear, twin-boom, from McConnell AFB.

The loss of the LOH competition and the obvious lack of any new and significant helicopter programs prompted me to start looking around for another job before the bottom fell out. The LOH was a magnet attraction so I applied to Bell and Hiller where I figured the light helicopter action would be the strongest. In August of 1961, I resigned from Cessna and moved to Palo Alto, California and joined the Flight Test Department of Hiller Helicopters.

Skyhook ad in the December 1961 issue of "Flight."

Phil Stehle was the Manufacturing Planning (Tool Planning) group leader for the production of the CH-1C at the Cessna Prospect plant, moving to the helicopter from T-37 Tool Planning. Phil has provided some recollections of his Cessna helicopter experiences. He remembers a test flight with Jack Zimmerman in December 1961. Phil left Cessna about that time and took a job with Kaman. Interestingly, there he met Seibel's cohort from the Seibel Helicopter days, Red Lubben. Here are Phil's comments:

The hollow spar/leading edge of the rotor blade was open at the inboard end and was to be plugged with an expandable rubber plug. I well remember the time when somehow one blade had no plug, whether omitted or not tightly enough installed. The test flight proved the efficiency of the blade as a centrifugal air pump! Fortunately, the trailing edge of the outboard end of the blade stayed bonded although the tip end blew up like a balloon. Thanks to Jack Zimmernan's skill he brought the ship back to the plant. He exhibited another skill in expressing his disappointment with the blade assembly people. I was in the planning office at the time and so missed extending my vocabulary beyond what I had learned in the Marine Corps.

When Cessna decided to go into helicopter production I was selected to be group leader of the tool planners that would participate in the program. My boss told me to go over to Engineering and get acquainted. Like the country bumpkin I am, I presented myself, I believe it was Mel Vague, and smart-assedly said , "I don't know anything about helicopters except they fly straight up." I got a long look , then the comment, "They don't want to, you have to make 'em do it." That was the start of my education in rotorcraft.

The Continental engine required additional cooling in hover or ground runup. A big ring fan ran at high rpm to blow air across the horizontal cylinder cooling vanes. This fan was around two feet or more in diameter and had, I think, forty-eight blades, looking somewhat a jet engine compressor ring. The ring was centrifugally cast of epoxy with a reinforcing wire and fiber roving,which might have been Kevlar. This was a delicate and difficult piece to make. When we were starting up the process I was called to the office of Otto Irby, Plant Superintendent/Works Manager. He asked me about the fan and how many I planned to make at the start. I told him four since that was the first production lot. He said to make an extra and bring the first to him. Well, it wasn't healthy for career planning to argue with Otto, so I did as told. When the first one passed inspection I took it to his office. He thanked me, put on his hat and went out the door, fan in hand. I later heard that Del Roskam had told Otto that his guys at the Prospect plant would never be able to build that fan. The rumor was that Otto walked into Del's office and hung the fan around Del's neck, then walked out. I never saw that fan again.

FAA production certification inspector was a lanky Oklahoman named Joe Bonk. Seldom smiling, he was a taskmaster that insisted everything be exact and repeatable. Up til then we had all been involved in military A/C and the documentation was up to others. Joe required each tool and process to be written. If he found a gadget of aluminum painted red that some worker had used to facilitate his job, it had to be given and identity and listed on the process sheet. Joe rode me and my guys pretty hard. We decided to write the assembly logs in such a way he COULDN'T disapprove. We listed tools, optional equipment kits as required by the ship order, and lots of other info. We put in underlined blanks at the appropriate place for recording serial numbers of components etc. Heck of a chore for us country boys, but we heard later that Joe said they were the best he'd seen.

The brown and yellow ship pictured on your web site was number one production unit and was painted in those awful colors, we were told, to celebrate the Kansas Centennial in 1961.

Phil Stehle has also kindly provided some entertaining anecdotes from his work in manufacturing; you can find his tales of production floor hijinks in Appendix One.

The Air Force was responsible for engineering flight tests on Army helicopters. The CH-1C version, with mechanical gyro corrections to the adverse roll input from power changes experienced on previous models delivered to the Army,was retested at AFFTC Edwards AFB between October 1961 and May 1962 (YH-41 Number 4244). According to a report by flight test engineer Rob Ransone, a pitch horn failure occurred during one test flight, this failure causing vibration and concern similar to the early test flight failure suffered during a CH-1B xc flight piloted by Jack Zimmerman. Apparently the interblade damper froze causing the failure. The pilot on this flight was Bob Baldwin. Does anyone have the Air Force report of this retest?


Twenty-three civil CH-1Cs are reported to have been delivered (sold) by Cessna, most in 1962. Can anyone provide the exact number by serial numbers?

1961 printing of manuals shown above. The 1962 issue had a different cover design.

Cessna CH-1C production model shown in Denver in 1961. Photos by helicopter enthusiast Bill Lyster.

The Skyhook was presented at the 1962 Helicopter Association of America convention with two ships giving demonstrations.. The picture below, taken at the January, 1962 HAA, shows the Skyhook along with its major 1962 competition, the Hiller UH-12E4 and Bell J models.

Aviation photographer Chad Slattery kindly provided pictures of a 1962 Cessna 5" x 8" promotional postcard which is from the estate of Al Vopal who ran Custom Models in Macedonia, Ohio; Al made many models for Cessna but Chad can't recall seeing a Skyhook model. The back of the card has a rather flowery sales pitch for the Skyhook - I'm sure this text (see below) must have given a few helicopter operators a good laugh.

Presenting the Cessna Anniversary Model Skyhook... World's Finest Four-Place Rotary Wing Aircraft!

The Skyhook is a perfect answer to man's ages old quest for taking the shortest distance between two points. In a Skyhook, you can gracefully climb up and over the congestion of the city or over bridgeless rivers with equally nimble ease. If you're involved in production, you can go from plant to plant...if you're in merchandising, you can go from store to store...and if you're in sales, you can literally go from door to door...and all directly...without wasting so much as a minute, a step or a penny in unnecessary travel time, effort or money!

With the Skyhook you can lop hours of costly on-the-job commuting from your schedule. You can haul loads, survey building or development sites, link out-of-the-way facilities with the home office, or take advantage of your pick of a thousand other ingenious uses discovered by others. Or better still, invent a brand new application for the Skyhook, yourself.

Start now. Plan to attend the special Skyhook showing as my personal guest. See the world's finest four-place, rotary-wing aircraft...the Cessna Skyhook for 1962. I'll be looking for you.

Skyhook promotional postcard for the 1962 model.

It has been reported that the Skyhook experienced numerous engine problems in actual service; the Continental FSO-526 at 3200 rpm apparently ate up cylinders, broke rods and a crankshaft failure was experienced - the 526 experienced fatigue failures from inertial loading at high rpm and low power, a common helicopter situation. The Skyhook was operated at the 1962 Seattle World's Fair by Seattle Helicopter Airways, Inc. as official transportation; the photo below is from a postcard. Incorporating five seats, it is reported that 10,000 passengers were carried during the fair by three operating Skyhooks. A helicopter charter poster from 1962 is also presented below.

Detail of CH-1C from postcard.

Bruce Craig remembers riding the Skyhook as a youth in 1962. This photo was submitted by Mr. Craig.

Bill Cotter has kindly provided the photos below which show the Cessna helicopter operation at the base of the Space Needle, next to the Plaza of States, during the 1962 Seattle World's Fair. Note that two helicopters share the heliport. Additional photos at Seattle appear further down on this page.

A serious CH-1C accident happened in October 1962 in the Gulf of Mexico. A Skyhook on floats crashed into the Gulf with the loss of four lives. Only a few small parts and the floats were found and it was assumed that an engine failure resulted in a misjudged water autorotation landing attempt. November 2003: I've received a communication from James Brown of Lorain, Ohio who was three years-old when his father, Frank Gilbert Brown, was killed piloting this CH-1C in the Gulf. James would appreciate any information possible about this accident which is no longer carried in NTSB records. A CH-1C operator, Max Sonnenberg (as mentioned further down this page), gave Frank Brown a ride in the Cessna just a week before the gulf crash. Max, in an interview, has stated that Frank was a very competent pilot.

Production CH-1C on floats. Photo courtesy of Gary Cheatum via Bob Smith. Cessna mechanic, Zane McAnelly, used his 1959 red and white Crosby boat as a support craft during CH-1 float testing at Fall River Reservoir; Zane had a place on the lake. He used some surplus CH-1 hydraulic parts to replace the sticky, cable operated throttle on his boat. Thanks to Matt Menges of Wichita for this info on Zane; Matt, a family friend of Zane and his family, is now in possession of the Crosby boat.

Another nice photo of production CH-1C, N5701, provided by flight instructor Don Burwell.

New spray rig for Skyhook is shown in mid-1962. Permits normal coverage of 190 acres per hour in 70-foot swaths. Owned by Sky Hook Inc. of Durango, Colorado. Rig has 20-foot booms and two 45-gallong tanks.

Max Sonnenberg started Sky Hook in 1961 with a Cessna CH-1C. He learned to fly helicopters from Hersey Young in Denver and he purchased the ship from Hersey on a $79,000 handshake! In a recent conversation with Max, he praised the CH-1C as his start in the Durango, CO business doing agricultural spraying (with a self-made rig) and other charter work but condemned the CH-1C as having a woefully bad Continental engine and exhaust system. In less than 200 hours of operation, Max suffered six emergency landings from major engine problems including a broken rod that popped through the top of the crankcase. He made several autorotation landings in hair-raising situations with no injuries to himself or the helicopter. His engine problems were discussed frequently with the FAA and Cessna, including Dwane Wallace; Continental tech reps even worked on his supercharger resulting in one of the failures. The last engine failure over a golf course convinced Max to quit using the CH-1C; he left the ship where he autorotated and apparently Hersey Young, Cessna and the bank came to some sort of agreement as he walked away from the deal. Max then bought a Bell 47G3B which he didn't like as well as the Cessna but which had a vastly better engine even though its performance and handling was inferior to the Cessna. Max had one ground fire with the CH-1C started by the under fuselage exhaust outlet - he made a "fix" by running both exhaust pipes out the side of the cowling; the FAA noted that he shouldn't fly at night because of the exhaust flame! Max's sad operational history with the CH-1C points out the fact that the Continental engine problems were never adequately solved and that the operators were doing the service test. As is usually the case, factory test ships didn't demonstrate the problems to the extent that field service proved.

Max Sonnenberg retired from his Sky Hook helicopter business in 1986 and the business has successfully continued to this day. Max said his best helicopter, with the least problems, was the Sikorsky S-61.

Do you have information? There is a report that Alaska Coastal Airlines in Juneau, Alaska was considering a Skyhook (must have been 1962) - or perhaps bought one as a dealer - and the ship suffered an engine failure and plopped into the harbor and sank but the crew survived with no injuries. Is this true? Can you provide further info?

As 1962 was coming to an end, Cessna announced the new CH-1D model for 1963 which incorporated improvements; this new model was not available at the annual sales meeting in October. A new engine drive shaft to absorb torsional vibration, a rotor brake (we worked on that in 1961), an increase in gross weight to 3250 lbs., and a beefed up engine, the Whirlaway, which sported heavier connecting rods and bolts, heavier cylinder barrels, new supercharger clutch, new crankshaft damper weights, and double breaker mags.

CH-1D Continental Whirlaway engine installation.

Also incorporated in the CH-1D was an awful exhaust system which overcame the objections of the low, under fuselage exhaust stream. An exhaust pipe collected the gases in the collector/venturi box, was routed under the fuselage to the tail boom where it made a 45 degree angle change upwards, disappearing into the tail cone, and exiting above the tail cone (shown in the picture below). As I mentioned in the beginning of this article, the exhaust problem was never solved and this terrible arrangement only proves the point. This must be the reason for the gross weight increase! The "D" model received certification on December 24, 1962. With the "D" certification, there were six CH-1 models listed on the type certificate.

A magazine advertisement for the 1963 CH-1D Skyhook

The Helicopter department was also involved in advanced projects in the 1962 period as shown below.

Cessna "Kinedyne" proposal. Following the unsuccessful 1961 bid for the LOH contract, the helicopter R&D efforts went into a replacement for the aging Army L-19 liason aircraft. A sort-of autogiro, the "Kinedyne", was proposed in 1962. This machine was turbine powered, had counter-rotating props for thrust and used a heavy, high inertia rotor which could be run-up for takeoff and would have adequate energy for near-hover landings. The trademark rotor system of the CH-1 was not evident as a completely different rotor was envisioned. Directional control in-flight was obtained by a rudder-like surface while directional control in the low-speed flight regime was gained by use of a torque control unit clutched to the main rotor. In hindsight, this proposed aircraft does not appear to be a very practical machine with far too many complexities for a two-place observation craft. Drawings of this proposed aircraft appeared in the Spring 1962 issue of "Air Progress."

Don Burwell became a CH-1C flight instructor at Cessna in 1962. Don has kindly submitted the following comments concerning his brief employment with Cessna; I believe that he would have worked for the Sales Department as opposed to the Helicopter Division but I'm including the instructors in with Division personnel. Actually my use of "Division" is incorrect inasmuch as once production of the CH-1C started, the group became a "Department".

Don writes, " It is my understanding, the original Skyhook sales and training personnel were taken out of the ranks of the Cessna fixed wing division. Have no idea who trained them. This just did not work and some accidents occurred.

"A decision was made to search for someone who could revitalize the entire program. This resulted in the hiring of Ed MacKenzie. Ed was working for Southern Airways as a helicopter flight instructor and flight leader. Southern Airways had a civilian contract to teach Army personnel to fly helicopters at Camp Walter in Mineral Wells Texas. Ed's main duty at Cessna was chief helicopter instructor. Soon after, he was put into charges of sales and I was hired as the chief instructor. I was also a helicopter instructor at Camp Walters. Not sure how much flight time Ed had, but I had been flying helicopters in both the Navy and at Camp Walters for seven years and accumlictated over 8,000 hours. I am sure Ed had more than that.

Cessna received an FAA Approved Flight School Certificate in the spring of 1962; the school had been operating since August, 1961. The photo above shows The FAA General Aviation Operations Inspector, Theo Moore (R) presenting the Flight School Certificate to Dr. Robert McCormick, Cessna Director of Training and Edward MacKenzie, Head of Rotary Wing Flight Instruction. The school was part of the Cessna Marketing Division's training department and included both flight and maintenance training.

"Everything was put into place to make the Cessna helicopter program a success. It just did not happen before management pulled the plug. Sometimes I wonder if management even knew that Ed and I were there to reorganize the program.

"Ed was checked out by the test pilot and I was given a briefing and a one hour check ride by Ed before I felt comfortable with the Skyhook. My time was very short with Cessna, and once they dropped the program, they wanted to get rid of and erase an existence of the helicopter. All pictures and literature were ordered to be destroyed.

CH-1C alongside the Cessna Wallace Plant.

"Most of my time was spent demonstrating the Skyhook to potential buyers. As it turned out there was only one sales while I was there. I don't remember who the purchaser was, but they sent one of their employees to be trained. Using my experience and the flight training manual as a guide, the employee was able to solo without any difficulty. I would only guess that he was given about twenty hours of instruction. The cost was included in the total cost of the Skyhook. New owners were also given an extensive ground school training on the maintence of the Skyhook. Can't remeber the name of the ground school instructor, but he was also hired from Southern Airways.

Rotary Wing Flight Training Program certificate for the "Skyhook".

"Ed remained with Cessna and became a very sucessful sales person before becoming a dealer for Cessna and then later for Beech aircraft." Thanks Don for your insight to the sales effort at Cessna. Ed MacKenzie relates that he accumulated more than 500 flight hours in the Skyhook during his 15 months with the program and that he demonstrated the Skyhook from coast to coast. He experienced one flight incident which he describes as "unsettling"; lifting off to a hover, he lost hydraulic control boost, having to muscle the ship safely to the ground. A teardown inspection of the control system by Dick Ledwin and Charlie Seibel disclosed contamination in the hydraulic fluid. During our FAA flight tests on the CH-1, we had to demonstrate all flight maneuvers with the boost system turned off - loss of boost definitely resulted in high, but manageable, control forces.

West Coast Operations of the Cessna Skyhook. I recently had a conversation with Jack Coshow who now resides in Oregon. Jack was a P-38 pilot with the 95th Fighter Squadron of the famous 82nd Fighter Group of the 12th and 15th Air Force during World War II. Jack worked for United Airlines in quality control and was associated with a Cessna dealer, Sequoia Aviation, at San Carlos, California as a salesman in the early 1960s. Sequoia was owned by Lou Rohr and John Pritchard was sales manager.

Jack was with Sequoia - his first job in aircraft sales - when Cessna began delivering Skyhooks to dealers in the 1961-1962 era. Three Skyhooks were originally used as helicopter demonstrators on the West Coast. One at San Carlos, one at Van Nuys and one in Seattle. Sequoia Aviation was convinced that the Skyhook's superb altitude capability would result in sales in the Sierra; as far as Jack remembers, however, no Cessna helicopters found customers anywhere on the West Coast.

The Seattle World's Fair created a passenger market for the Seattle dealer and, as mentioned previously in this article, a brisk helicopter business was created giving passenger rides from the waterfront with a trip up around the needle. The Seattle Helicopter Airways operation was able to get FAA approval for a rear "bench-type" seat which then allowed four passengers to be carried in addition to the pilot - a real money maker. Long lines waiting for a ride convinced the dealer to get another Skyhook and apparently Cessna found another machine to provide the operation. Continued passenger interest resulted in the Seattle dealer contacting Sequoia Aviation and leasing Sequoia's Skyhook for a total of three working machines giving rides.

Postcard from the Seattle World's Fair

Previously unpublished photos (above and below) by Jim Larsen of the CH-1C of Seattle Helicopter Airways using the helipad at the Space Needle during the Seattle World's Fair.

Up close on landing! Photos by Jim Larsen Aviation Photography.

Go to this page on the website for the Space Needle and click on the third movie short (two kids) and about nine-tenths the way through the short one-minute clip you'll see a Cessna Skyhook on approach in the background. Skyhook approach.

Several video scenes of CH-1Cs at the 1962 Seattle World's Fair may be viewed by clicking here. The helicopter scenes are at 01:35 minute, 5:07 and 18:21. The 5:07 shot is from the Space Needle looking down at the helicopter landing on the pad.

About this time, a potential customer in the Reno area asked about the Skyhook so Sequoia made a deal to borrow the ship from Van Nuys in order to give a demonstration. Sequoia's chief helicopter pilot, Jack Loney, and Jack Coshow departed SFO on an early morning DC-6B to LAX with the intention of picking up the Skyhook and making it back to San Carlos that same day. Things went awry!

A nearly empty flight on the 4-engine Douglas so the stewardess invited the duo to sit up front in first class, a nice gesture. However, not so nice upon landing as the front tire blew and the business end of the airliner got shook pretty hard! Stuck on the runway, Jack and Jack didn't make it to the terminal to pick up their ride to Van Nuys on time. A phone call and wait eventually got them to Van Nuys where Loney inspected the Skyhook and determined that it was due a 25-hr. check. So they waited for the mechanics to finish off the check before getting ready to depart. Seeing that there was no way they could get back to San Carlos, they decided to RON at Oxnard; Loney called a motel on the field and made arrangements to set the helicopter down on their motel lawn.

Flying in to Oxnard, Loney wisely decided that the postage-stamp size lawn wasn't going to work as a landing site, so requested an air taxi to the local FBO. Hovering across the airport, the two Jacks saw a crowd and a red truck waiting for them on the ramp - such a reception! Turns out that at the 25-hr. inspection at Van Nuys, a mechanic failed to securely tighten an oil line and leaking oil was causing smoke to trail the Skyhook giving rise to a fire alarm by the observant tower operator. They made it back to San Carlos the next day - that helicopter wasn't sold and became one of the four on the West Coast that were bought back by Cessna in early 1963.

Jack Coshow fondly remembers the Cessna Skyhook and still has some memorabilia associated with the machine. He got about 5-hrs of dual and regrets never getting completely checked out in it.

More Sequoia/Skyhook connections: Richard A. "Dick" Bridgeford was the originator of the highly successful Bridgeford Flying Service at Lake Tahoe, Stockton and Napa airports; Dick has recently written of his aviation experiences in a published book, Living the High Life. He obtained a helicopter license as part of a Brantly Helicopter sales outlet deal. BFS was a Cessna dealer at Stockton and Dick flew with Sequoia's chief helicopter pilot, Jack Loney, in a Sequoia-owned CH-1C to Lake Tahoe to demonstrate the ship to Bill Ledbetter of the Harveys Resort Hotel; they flew to the hotel parking lot, demonstrated the helicopter, and flew back to Stockton. This would have been in 1962. Dick has provided me with the two photos shown below, taken at that time. Dick Bridgeford is the gentleman standing on the left.

This ad by Lane Aviation Corp. of Columbus, Ohio appeared in the October, 1962 issue of "Flying" magazine, page 91. Lane was another of the Cessna dealers who bought a Skyhook. Can anyone add information?

Received the following comments from Bill Evans in February 2006: " I really enjoyed reading your web page about the Cessna Skyhook. Executive Aircraft which was a Cessna dealer in Kansas City, MO had a Cessna Skyhook. It was operated by a pilot by the name of Jerry Getz. He was probably one of the few operators with any degree of sucess with this helicopter. Later when Cessna recalled the remaining aircraft and bought them back he became a professional witness for Cessna in many of the lawsuits that came about. I did some flying with Jerry Getz in the early sixties and he had many good stories about flying the Skyhook."

The decision was made on December 26, 1962 to kill the Cessna helicopter program entirely. Accumulated problems, poor timing, looming turbine-powered competition, lack of sales, a poor fit in the Cessna company, loss of any potential military sales, or maybe conflicting attitudes in management - whatever the reasons, Dwane Wallace, chairman of the Board, made the announcement in January 1963. All existing civil CH-1s in the field were bought back by Cessna in order to eliminate any ongoing servicing support (and product liability!). The returned ships were scrapped along with unsold inventory (a Kansas correspondent wrote that when he was a very young lad, he remembers seeing Skyhooks piled in a Wichita wrecking yard. Now, if we could locate that yard, old records might exist indicating how many were scrapped). Subsequent information comes from Leon Bowman who worked at Cessna from 1964 to 1974 - he remembers seeing a CH-1 fuselage in a wrecking yard on Waterman Street between Broadway and the railroad tracks on the north side of the street. Does anyone else have a recollection of this salvage yard? Correspondent Robert Peffer, who worked at Cessna from 2000 to 2008, mentions that erosion from rain had washed away soil in an area behind what is known as the "glass house" at the Pawnee plant, and that some helicopter remains were unearthed (blades etc.) - landfill regulations required that the area be maintained as a fill and a clay layer has been added along with a concrete channel. Rumor is that the Skyhooks returned to the factory were buried at that spot. Does anyone have confirmation of this? If so, please contact me.

The end of the line for the Cessna helicopter - a rather sad way for a record setter to die. Cessna, however, did continue to deliver MAP helicopters to foreign countries into 1963 and I have no idea how these were supported. The high altitude (or hot weather) capability of the Cessna made the ship popular with MAP users and more could have been sold; also, the Army had a continuing interest in the CH-1C as an instrument trainer. It is estimated that a total of somewhere between 47 and 50 CH-1's of all models were constructed but the exact number is not known nor is it likely to be known - there were ships in construction at the time of the shutdown that would have received serial numbers. Charles Seibel is quoted as saying that there were "approximately fifty" built.

To add further to the saga of the CH-1's demise, Cessna cancelled the CH-1 FAA Type Certificate, 3H10, in 1989 thereby removing the Cessna Skyhook from all records.

Note: Charles Seibel and Sanford Hinton, prime movers of the helicopter division, are both deceased. Seibel had a large archive of photos and movies of the CH-1 project - the whereabouts unknown of the originals but Seibel made a video in 1991 using much of his material. Jack Leonard took a position as manager of a new eastern office in Washington for the Hughes Tool Company after leaving Cessna in early 1962 - he became responsible for coordination of the company's military programs in the eastern states.

Charlie Seibel and San Hinton, about 1955, discussing the BLC program.

Charles Seibel with Arthur Godfrey in 1957. Do you remember Arthur Godfrey? He made an interesting film for Eastern Air Lines in 1953 which featured the Super Connie along with notables Capt. Dick Merrill of Eastern, Capt. Eddie Rickenbacker, Chairman of Eastern, and Tony Levier; the movie, "Flying With Arthur Godfrey," takes you on a typical flight to Miami on the Connie. Godfrey owned a grass strip in Leesburg, Virginia which has become the Leesburg Airport. Godfrey was a qualified Navy pilot and flew a DC-3 and Navion out of his "cow pasture." You can watch this entertaining movie at

CHARLES SEIBEL - Post Cessna. A little note of interest. Seibel went on to Bell Helicopter from Cessna and he developed the Huey Cobra in short order, a huge success for Bell at the time. Seibel was the Chief Experimental Project Engineer and was given the job in 1964 to investigate an improved version of the UH-1B in the weapons role. The prototype HueyCobra was started in early 1965 using many components from the UH-1C helicopter. Prototypes were flown with both retractable gear and skids during the development program. In February 2004, the new CEO of Bell, Mike "Red" Redenbaugh, had the following exchange in an interview with a Defence Helicopter magazine reporter who queried, "The thing about the Huey is they got it done in months (Vietnam), the attack one as well. Here we are on Year Fifteen, or something, on LHX-Comanche. Crazy stuff..." and Mr. Redenbaugh answered, "You hit an intriguing question and in fact just yesterday I asked them to go back and pull the supplementary data on all that. When you want to go down the road ahead, sometimes you ask the people coming back what they saw! There's a lot of history, a lot of passion to the Huey. I want to 'reach back' and see what they did." Well, "Red", Charles Seibel was the reason that the HueyCobra program was so successful so quickly as you will no doubt find out. The industry today needs people who know how to get things done but the existing corporate culture and military complexities stifle the "free enterprise" approach that was used by Seibel and many others such as the Lockheed "Skunk Works". Mr. Redenbaugh abruptly resigned from Bell in January 2007; the resignation is said to be linked to Bell's lagging timetables for Marine and Army projects.

Siebel made an excellent video in 1990 concerning the development and production history of the Cessna CH-1 helicopter; this vide may be viewed by clicking here. Use the back arrow to return. Note that the download takes awhile.


In comparing the CH-1C with its 1961 competitors, the Hiller UH-12E4 and the Bell 47J-2, I've had the opportunity to be associated with all three machines on an engineering basis. I taught maintenance on the H-13 for awhile in the Army and later did an STC on a conversion of the 47J to a 47J-2 equipped with the supercharged Lycoming from the 47G-2A; a similar version of the J was built by Agusta in Italy designated as the 47J-3B-1. Except for the Lycoming engine, the Bell 47J-2 did not measure up to the Cessna; handling and performance were far superior in the CH-1C and I've never been a Bell fan when it comes to maintenance and durability. The supercharged Bell that I STC'd had decent performance but lacked tail rotor power at altitude. The Hiller E4 was not supercharged so lacked the performance of the CH-1C and there was no question that the flight characteristics of the Cessna were superior. The Lycoming engine of the E4 was not without problems but was more reliable than the Continental 526 (perhaps the beefed up version in the CH-1D would have solved the problems). I preferred the cabin arrangement of two x two in the Cessna to the one x three in the others dictated by cg considerations. The Hiller machines were very rugged and would probably stand up in the bush better than the Cessna and the Hillers were quite reliable brought about partially by years of experience that the Cessna didn't have. The Hiller UH-12L4, sometimes called the SL4, with its supercharged Lycoming and stability augmentation, would have been formidable competition had the Cessna hung on for another few years. My company, Progressive Aviation, owned both a Hiller E4 and an SL4 (both in experimental category) - we used them for experimental test programs. I'm probably biased, but I'll call the CH-1C the winner in the looks and flight department, but if I had to choose only one ship to take to a job, give me the Hiller SL4.

In most short articles about the Cessna helicopter, published in the last twenty years, it is commonly assumed that the CH-1C was overpriced (leading to its demise) and frequently a comparison is made to the much lower price of the Cessna 310. Ever notice how some people blather on about things they know nothing about? First of all, the helicopter was not in competition with a 310 or any other airplane; the CH-1C had to be priced in competition with other 4-place, like helicopters. The basic price of the CH-1C, as posted in 1961-62, was $79,960.00 (For both the Cessna and the Bell, figure on another $5,000 at least to equip for normal operation). I don't happen to have on hand the 1962 brochure for the Bell 47J-2 Ranger, but I think it's instructive to take a look at the 1959 Bell 47J Ranger, the commercial introduction year for this 4-place helicopter (the Navy bought 47Js in 1957 which paid for its development (and HTL-7s for instrument training in 1960) - the 47J was used for presidential travel for a few months in 1957 also but Eisenhower soon switched to the S-58. The two UH-13Js were retired in 1967 with one going to the NASM (57-2729) and the other to the Air Force Museum (57-2728). Eisenhower was the first chief executive to fly in a helicopter.). The picture below is from the Ranger brochure for 1959; this ship. "Equipped with metal main rotor blades and optional 35 or 49 gallon fuel tanks on skid landing gear (2850 lbs. gross weight, 240 HP)" was priced at $69,500.00. The J version had the unsupercharged Lycoming 435 engine with 30 less rated h.p. than the Cessna Continental 526. The gross weight of the J was only 2850 lbs. compared to 3100 lbs. for the Cessna and the J carried 10 gallons less fuel. The Bell J, at its maximum gross weight of 2850 lbs. would only hover in-ground-effect at 4,800 feet while the Cessna at 3100 lbs. had an in-ground-effect hover ceiling of 9,600 ft. (numbers for standard temperature). Of most significance for performance, the CH-1C could hover at 6,500 ft. on a 95 degree F day! The CH-1C could carry more, go faster, fly higher and carry passengers in a more comfortable cabin (the Ranger required passengers to sit three-abreast). A $10,000 difference in price which doesn't take into account the two-year difference in this comparison; add-in a larger engine with supercharger and the control ease of the Cessna's mechanical stabilization and the difference disappears. So much for the "high price" - compared to what? The Bell 47J-2 was introduced in 1960 and in 1961 I believe it was offered with the larger Lycoming VO-540-B1B engine derated to 260 h.p., a higher inertia rotor and hydraulic boosted controls; the 1961 Bell 47J-2 (gross weight 2,850 lbs.) was listed in magazines as selling for $69,950 (a helicopter with a close comparison to the CH-1C), essentially the same price since 1959. Another source lists the price of the 1960 J-2 as $72,500 plus an aditional $5,000 for a turbocharged 47J-2 which would bring the price up to $77,500, nearly the same as the CH-1C. Was potential competition from Cessna or Hiller the reason for this Bell price stabilization? By 1964, the Bell 47J-2A version had a list price of $72,950 with turbocharger (s/n's 3108-3132). Also of interest in this price comparison, the Republic Alouette II with turbine engine (gross weight 3300 lbs) was listed in December 1961 as being priced at $105,480. If you have any additional Bell pricing information, please let me know.

1959 Bell Ranger.

Bell 47J-2 from December 1961 ad in "Flight."

If you are interested in Cessna airplane development, I suggest the book, Cessna, Wings for the World, The Single-Engine Development Story, by William D. Thompson (1991). Bill Thompson was the Manager of Flight Test & Aerodynamics at Cessna when I was employed there and was the chief engineering test pilot. The book has several pages devoted to the CH-1 in an article written by Charles Seibel. Bill was no stranger to record flights as he set a world's altitude record for lightplanes in 1953 by reaching 37,063 feet in the Cessna XL-19B.

Cessna XL-19B with Boeing 502-B gas turbine engine.

Cessna built the 195 up to 1955. In 1952/53, as I walked through the Pawnee assembly line on the way to work, there was a small area which was devoted exclusively to constructing 195s - usually about three airplanes total, from a jig to a completed model receiving finishing touches - about like you'd build one in your garage. These were probably built with more care than any other Cessna airplane. The photo above shows serial number 16046 which was built in 1953; this photo is from a Christie's 1990 catalog where the airplane was being offered at auction in Duxford. A three-view of the Cessna 195 can be viewed by clicking here. The 195 was one of the cleanest designs Cessna ever made.

EMPLOYEES. This is a listing of Helicopter Division or Department employees who worked in engineering and in the shop through about 1962; the list covers most everyone that I could find on documents of that era. John Alexander, F.L. Ambler, Ed Baumgartner, R.L. Boyd, Harold Bull, K.E. Burris, Bill Carlson, Ginger Carson, R.F. Clark, Marvin Colaw, Bennett Connet, Harold Connet, Jr., Ralph Davis, Harold Farthing, Don Ellis, D.D. Granger, Sherman Graves, Jim Griswald, Charles Harris, San Hinton, Fred Hladik, Dorothy Harlow, Tommy Howland, D.E. Hoyt, Thomas Hsueh, C.Lee Kennedy, Michael Knott, Richard Ledwin, Jack Leonard, H.W. Lee, Don Lodge, Charles Marsolf, J.D. McConnell, Zane McAnelly, Blanche Miller, Walt Olds, Mark Wheat (1954-55), Mel Osborne (tech rep), George Palmer, J.J. Pohlen, B.E. Rambo, Stephen Remington, Vern Roush, L.A. Seburn, Charles Seibel, Sid Shannon (sales), R.T. Shaw (pilot), Robert E. Smith, G.W. Stephens, Charles Tucker, Melvin Vague, Red Wehrenberg, Jack Zimmerman, Frank Robinson, John Parks, Elwin Reichert (pilot). J. Bruce Learmont (who went to work in the department about the time I departed) has added some other names; Frank Brown, Wayne Speilkert, Regene Prilliman. Sales Department flight instructors: Don Burwell, Ed MacKenzie, Jack Martin. William Robinson (tech rep I believe), R.T. Roberts (tech rep), Robert Pemberton (tech rep?). Some production people at Prospect plant: Phil Stehle, Dean Mallory. Anybody missed, let me know.

BOOK. CESSNA WARBIRDS - A Detailed & Personal History of Cessna's Involvement in the Armed Forces by Walt Shiel, softcover, published 1995, 328 pp. Available by contacting by email at or checking out This extensive volume covers Cessna's military aircraft efforts throughout Cessna's long history. It is well done and undoubtedly the only book of its kind; the L-19 and its variants and the T-37 and its variants are given major attention. The Cessna YH-41 story is given eleven pages. Walt Shiel did not have anything to do with the YH-41 so his historical information is extracted from contemporary documents, William Thompson's excellent Cessna book, military reports and personal interviews with people somehow associated with the YH-41 or second generation involvement. Some errors are bound to creep in in such an approach. In general, the presentation of some of the Army's evaluation of the YH-41 and comments relating to the Army testing are valuable and excellent additions to the story of the Cessna helicopter. Several errors beg mentioning however, so I'll note them here; this is not a criticism of the book but just an attempt to keep the record striaght. Charles Seibel's time line from college graduation in 1943 to the purchase of his company by Cessna in 1952 is covered on this website. Shiel's chronology is off, a minor point, but significant. Shiel was deceived by publicity, just as was planned as I pointed out in the altitude record attempt section above, and writes that the altitude record was set in a YH-41. An Army pilot, yes, but a YH-41, no. Jerry Pohlen's name is given as Polen. The CH-1C instrument certification required much more than, "...a few minor additional modifications..." to the CH-1C. A paragraph on the landing gear states that it, "...consisted of a single piece of 3.5 inch steel tubing..." and that it "...was prone to damage..." and that "...whever the gear was damaged beyond repair this entire assembly had to be replaced..." These statements are entirely incorrect. In fact, the YH-41 heavy duty landing gear strut castings were restrained by stainless steel "tension straps" which deformed (stretched) under hard landing conditions. In the event of hard landings, the gear was undamaged and all that had to be replaced were the simple and inexpensive straps which ran from the strut to fuselage support castings. Note that an increase in gross weight of 100 pounds for the not-to-be-produced CH-1D does not mean that the payload increased by 100 pounds. Although a turbine-powered CH-1 was envisioned and proposed, I am not aware that any designation of CH-41 ever existed. In any case, the photos and captions relating to the the "jet-engined CH-41" (page 289 and 290) are in reality pictures of the mockup for the LOH proposal, the CH-4, and did not "..retain the general arrangement, size and layout of the original YH-41..." as the engine was located behind the rear seats. Of particular interest to me, Shiel presents a breakdown of the CH-1/YH-41 production quantities and concludes that a total of 44 aircraft were built, the first total that I've seen and I have no reason to disagree with it although Charles Seibel, in 1991, recalled the production total as approximately 50. Shiel mentions that six Army machines were bought back by Cessna (I mentioned above that some were returned as I flew two of them) and that they were remanufactured into CH-1Cs, information that I was unaware of at the time I departed Cessna employment. The distribution of the eleven MAP ships, five to Iran (Army) and six to Ecuador (USAF) is also valuable information although that number may have been fifteen or more in total including South America.

Walt Shiel wrote a fine article on the CH-1 for the September 2003 AIR&SPACE magazine. Under the "Oldies & Oddities" section on page 18, Walt's article is entitled "When Cessnas Wore Rotors." The one-page article is entirely accurate and is shown below.

Flying Army - The Modern Air Arm of the U.S. Army by W.E. Butterworth is a very excellent book published in 1971; the author presents an accurate history of the Army's air arm up to 1971. Included is a nice picture of YH-41 64238 and a brief mention of both the Seneca and the Seibel YH-24 (with a picture). The development of Fort Rucker and Cairns Field is nicely covered. My old commanding officer, Colonel Robert Williams, president of the Army Aviation Test Board, (later became a general) is pictured receiving his Master Army Aviator Wings.

Military Helicopters of the World - Since 1917, by Norman Polmar and Floyd Kennedy, Jr., published in 1981, is an authoritative book which has an accurate, one-page description of the Cessna CH-1, YH-41 Seneca (page 206) with a photo of Army s/n 64241.

Another book. So far in this article, the books mentioned above by Walt Shiel, Norman Polmar, W.E. Butterworth and William Thompson, although punctuated by a few errors, are worthwhile contributions to the history of the CH-1. However, the book Closet Cases, by Randy Mertens, Second Edition 1982 published by Pilot News Press, devotes 2 1/2 pages of almost total disinformation to the Cessna helicopter. Merten's chapter on the CH-1 is a travesty with too many errors to mention. Not only worthless, this book contributes to confusion and compounds every piece of bad information ever written about the CH-1plus adds "facts" that are pure fiction. Pity the poor researcher that ever tries to glean some data from this piece of trash. Forget it.

Sikorsky VS-300A on temporary exhibit at NASM in 1990 - a CollectAir photo.

The Vought-Sikorsky VS-300 made a successful flight demonstration to the public on May 20, 1940. This event was written-up in the house newsletter of the United Aircraft Corporation, the Bee Hive. You can read this article by clicking here.

Mystery Aircraft. In keeping with the "forgotten aircraft" theme associated with the Cessna helicopter, the following picture appeared in the February 1994 issue of Pacific Flyer as the mystery aircraft. The blurb below the picture states that they're sure that this will stump the reader.

The CH-1 just won't die! The following question and answer is from the October 2008 issue of AOPA Pilot magazine in their "TestPilot" page 120. I take issue with their gratuitous use of the word "ignominiously" - perhaps an unfortunate demise but not one that can be described as "disgraceful" or "deserving shame" or "deeply embarrassing." - shame on AOPA!

The CH-1C is featured in the 2014 American Helicopter Society (AHS) calendar for the month of July. The ship pictured is a Canadian registered CH-1C, CF-OHE, and the photo is from the Mike Ody collection.

The Issue No. 3 of The Aviation Historian (April 2013) has a fine article entitled "Cessna's Whirlybird." This article by Editor Nick Stroud is nine pages in length and does an admirable job of recounting the history of the CH-1 in a necessarily short summary; I provided some of the photos used and assisted Nick in writing the article in the capacity of a "fact checker." The magazine originates in the UK and I highly recommend subscribing to this excellent aviation history effort. It is a quarterly, beautifully printed, is a bookshelf size at 6 5/8" x 9 5/8" and has a terrific selection of articles (not packed with redundant material). Check out this tome by clicking here for their website. Use the back arrow to return to this page.

LURE OF HILLER AIRCRAFT CORP. One of the major reasons for moving to Hiller as a flight test engineer was the award of the LOH contract. The picture below shows the prototype OH-5A on its First Flight on January 26, 1963 (just one month after Cessna shut down it's program), piloted by Hiller test pilot Larry Lape, a top test pilot in the helicopter field.

The photo below shows a model of the civilian FH-1100 taken at the Smithsonian's Udvar-Hazy Center in 2013.

Actually I was assigned to the "L" program while at Hiller doing test and certification on the UH-12L3 and SL3 three-place and the UH-12L4 and SL4 as pictured below in 1963. My company, Progressive Aviation Ltd., eventually owned this experimental ship, N90485, doing contract test work in the late 1960s. We also owned an experimental test E-4, N5323V, and did the FAA certification testing on the Hiller FH-1100. We also prepared and flight tested new L4's and E4's, which had been in storage, for customer delivery through the end of 1969 when the final delivery was made.

The photos below are of some of the Hiller ships that are in my logbook from the late 1960s. The E4 was prepared for a Mexican delivery. Photos were taken at Reid-Hillview Airport in San Jose, California.

Hiller UH-12SL4.

Hiller UH-12SL3, the best Hiller ever made in my opinion.

Progressive Aviation also operated a Hughes 269, N9357F, which was used for many types of commercial work including survey (see photo below), police patrol, bay water survey, charter transportation, etc. We later used Robinson R22s for flight training and general charter.

The following photos show another interesting project in which we were involved in engineering and development. Our past relationship with Fairchild-Hiller came in handy as I was able to obtain their permission to utilize all type data for the UH-12E in our program of FAA certification.

Progressive Aviation Ltd. was contracted by Alaskan operator Joe Soloy of Soloy Conversions to do the design and FAA certification of the Hiller UH-12E and E4 with the Allison 250 turbine engine replacing the Lycoming recip. Joe was a dynamo in action and he was a passionate advocate of this modification to the Hiller "E" which he had flown extensively over the years in Alaska. The program started and stopped a few times for reasons related to financial backing but certification was achieved in the 1970s. Soloy Conversions went on to not only build a large number of these conversions of the Hiller, but also did a similar program on the Bell 47. Joe Soloy passed away but the company still does business, mostly with turbine conversions of airplanes. The photos of the UH-12EJ5 above were taken at Reid-Hillview Airport, and vicinity, in San Jose, California.

From the September/October 1973 issue of "Rotor & Wing."

Concept model of the Soloy Jet 5 - 1967.

Some videos of a turbine powered Hiller E, along with a standard piston Hiller E, and other ships, are available by going to the video section of this website. Note that this Soloy conversion was licensed in the 1970's but is an active and viable, working helicopter today.

MODEL. The Cessna helicopter was the subject for a 1:40 scale plastic model produced by Life-Like Hobby Kits in the 1960s. This is probably the most bizarre kit ever produced. First of all, the kit was called Aerial Missile (Helicopter) with no mention of the YH-41 which it depicted, or the name Cessna, either on the box or on the instruction sheet. The actual helicopter configuration was fairly accurate and with a few changes a decent YH-41 could be assembled (see CH-1C version built from the kit in the photo below). However, the "missile" portion and its mounting was so idiotic that it could only be considered a joke. Reference to the box art below - imagine two giant missiles hanging on the tail cone! The helicopter in the artwork is reasonable accurate in its proportions but the artist omitted the air intake entirely. Then, for the real joke, checkout the pilot - oh, you can't find him? Well, he's the three-foot tall person sitting in the LH seat peeking under the middle door frame!

The above kit was purchased in the mid 1960s. Apparently the molds were originally made by Adams Action Models of Hawthorne, California. In fairness, the Adams catalog of 1959 gives Cessna a little credit. The copy for the "Aerial Missile Transporter", kit K-158 reads: "The 'Whirly Birds' are being armed to the teeth! Just recently the Army disclosed testing the use of the helicopter as a transporter of missiles such as the 'Hawk' and the 'Honest John', and as a possible rocket launcher. This Cessna-type 'Copter' has already broken height altitude, and other outstanding performance records. Scaled down to 9 3/4 inches in length this action model is loaded with features. 2 'Hawk' missiles, movable main and tail rotor blades; Pilot, Captain and Missile Loader. The model has a highly detailed engine, and removable hood for displaying it. Here is a 58-piece kit that includes decals and instruction manual to round out an action kit which will enhance any aircraft collection and bring any military line truly up to date."

Adams Kit No. K-158:98 Missile Transporter.

The Adams kit is dated 1958, just following Capt. Bowman's world altitude record flight which is mentioned in the Adams instruction sheet; the Life-Like kit doesn't mention Cessna at all. The two kits are pictured together in the photo below. Note that although the kits are basically identical in content, the Life-Like box has over twice the volume. The Adams kit has a realistic painting of the YH-41 (ignore the Hawk missiles!) - the Life-Like box art is horrible - too bad they didn't use the Adams box art.

The Adams helicopter also came in a "Fins-Props-Wheels" Gift Set of three kits, kit no. G-164 by Adam Action Models. The Adams catalog illustration and box art was a better representation. Mike Holdridge of Ithaca, NY reports that he has a similar kit made by SNAP Plastics of Hillside, NJ, identified as "Aerial Missile Transporter Kit #158-98. I would be interested in purchasing the SNAP kit.

Early CH-1C version built from the Life-Like kit in the 1960s.

Correspondent Bruce Craig took two photos (shown below) of a Life-Like 1:40 scale kit built to represent one of the CH-1Cs flying at the Seattle World's Fair of 1962; this nifty model was entered in the Oregon Historical Modelers Society IPMS Region 7 Recon at the Evergreen Aviation Museum, McMinnville, Oregon, in September 2008. Note what the builder had to say about the quality of the kit.

The Japanese toy manufacturer, Alps, produced a tin toy of the Cessna CH-1C; a somewhat "played with" CH-1C toy is pictured below.

An illustration from the CH-1C brochure.

CH-1C Drive Train


The photos below show some typical testing activity in the helicopter experimental shop at the Wallace Plant.

CH-1C stabilzer static test.

CH-1C rotating control system fatigue test rig.

Strain survey instrumentation on ptototype CH-1C coning tail rotor - 1961.


CH-1C 3-view from Service Manual.

CH-1C cyclic control system including rate gyro.

CH-1C Rotor Head.


This Appendix has the results of a commercial operator evaluation of the CH-1 and is followed by some entertaining production floor tales by Cessna employee Phil Stehle.

A look at the Cessna Skyhook from the commercial side.

Brent Wallace, a Canadian with a strong affinity for helicopters, has kindly provided an evaluation report of the Cessna CH-1 which was conducted by the Vancouver, B.C. helicopter operator, Okanagen Helicopters, in November 1960. This evaluation was made by the Okanagen staff. It's interesting to review the comments made about this helicopter by people who are studying it from the aspect of possibly purchasing the machine for their work. No sales pitch here - it's all about whether it can do the job!


A visit to the Cessna factory at Wichita was made by Howie Gatin and myself (L.M. Tillotson) on November 9th to evaluate the Cessna Skyhook and the following is an outline of my impressions from a pilot's point of view.

The Skyhook is a four place rotary wing aircraft powered by a 270 H.P. supercharged Continental engine. The supercharger is a single stage direct drive type and enables the engine to develop full horsepower to an altitude of 8000 feet. The engine delivers a full 270 H.P. to the drive shaft as it was developed and rated with the fan and accessories already incorporated.

A factory Specification and Performance sheet is attached.


The most impressive feature of the cabin and cockpit is the amount of room. There is plenty of room between the seats up front and good head clearance. There appeared to be just enough head clearance in the two rear seats. There is considerable space behind the rear seats for baggage. Both front seats are of the sliding type.

The mast projects vertically through the cabin near the back of the front seats. It is not objectionable as far as passengers are concerned but would be in the way if carrying internal loads of freight in the aircrafts present configuration. Future plans call for a utility model modified to facilitate loading. A cargo deck and large rear door for easy access would solve this problem.

Present doors are wide with easy access to both front and rear seats and have car type locking handles.

In the present configuration the pilot is seated on the right hand side. Cockpit layout is good and all auxiliary controls and switches are within easy reach. The instrument panel is of the fixed wing type with ample room for good positioning of all instruments. The aircraft we flew had dual instrumentation but production models will have a standard single layout. Instruments consisted of the standard layout as in the Bell with the addition of a clock and Rate of Climb. The latter will be optional on production models. A red warning light similar to that on the S.55 is used for transmission oil temperature.

Below the instruments are four push-pull controls, namely, carburetor heat, mixture, cabin heat and cabin air. Alongside is a key type ignition switch and cigarette lighter. Radio is installed in a pedestal below the instrument panel along with the Master and Generator switches, Slow Idle Switch, Auxiliary Fuel Pump, Hydraulic Shut Off and Electric Primer.

The ON-OFF fuel selector is on the floor in front of the cyclic and is of the standard fixed wing type.

Gas tanks are in the floor and hold 60 U.S. gallons. Saddle tanks on either side are optional and hold a total of 30 U.S. gallons. They have built in dip sticks attached to the covers. Saddle tanks empty directly into the main tank.


Cyclic incorporates a hydraulic system similar to the Bell. In addition there is a nine pound mechanically driven gyro connected onto the lateral hydraulics ahead of the cyclic stick to stabilize the aircraft in the rolling plane.

Due to the fact that the tail rotor is set well above the C. of G. there is a considerable rolling moment set up when anti-torque control is applied at high power settings. This coupled with tail rotor drift initially called for a fairly large stick displacement to the left. To compensate for lateral stick movement a lateral boost control had been incorporated. This consists of a cylinder and piston which is actuated by the difference in pressures across the supercharger which in turn has a direct realtion to the power setting. Any change in power initiates a movement of the piston which is combined through a mixing link with that of the gyro and fed into lateral cyclic.

An electric trim control actuated by a button on the cyclic grip relieves any loading whcih tends to build up on cyclic. We assume that these stick loadings, which build up to a minor degree especially during take-off and landing, are caused by the resistance of the gyro to any manual displacement of cyclic. When the button is depressed anelectric solenoid releases a ratchet and stick loading disappears.

Cyclic control is smooth and response is good. Although not quite as fine as the Bell a precision hover is not difficult. With hydraulics and gyro cut out control is similar to the Bell with irreversibles but there is much less feed-back. When hydraulics are shut off the gyro is also cut out due to the fact that the gyro feeds into the lateral hydraulics via the pilot valve.


Collective has an exceptionally long movement and is very sensitive. Only a very small movement is required to pick the helicopter up at gross weight. However, the overall movement is large when doing autorotation. Factory engineers say the sensitivity and small movement required at low altitudes is due to the fact that the Skyhook was designed around an operating altitude of 8000 feet A.S.L. Correlation of pitch and power is excellent. A change of approximately 7" H.G. can be made without winding on power before revs decreases an appreciable amount. Throttle control is sensitive. The started button is built into the end of the throttle grip.

A free floating stabilizeer is used which is free to take up its own position at speeds below 30 knots. Above this speed a bellows arrangement actuated by the slip stream forces the stabilizer in a streamlined postion against a stop. The stop is positioned (through mechanical linkage) by collective. Thus the angle of incidence of the stabilizer alters with collective pitch to reduce trim changes with power and help govern longitudinal stability.


Pedal control feels similar to the Hiller 12E and due to a large tail rotor (7' in length) it is very effective. Only a small amount of pedal is required to hover the machine at gross or when in autorotation. There appeared to be a good reserve of anti-torque control at all times. Pedals have a simple fore and aft adjustment.

A manual trim control of the type used in light aircraft has been installed to permit feet-off flying regardless of C. of G. or wind conditions. This control is situated forward on the extreme right.

It is quite obvious that most of these stabilizing and trimming devices are incorporated to permit easy and "hands off" flying. Cessna engineers claim that unserviceability of any of these items, other than failure of the hydraulics system, will not ground the aircraft. All appear to be of simple construction. Total weight of these devices is about 25 pounds. Some may be made optional on a utility model.


Starting, warm up and operation of the power plant is smooth and generally vibration free. A spring loaded slow-idle switch allows the engine to idle as low as 900 R.P.M. for warm up, and there is no clutch drag below 1250 R.P.M. Clutch engagement is similar to the Bell. Once R.P.M. have been brought up the slow idle is incorporative and engine revs cannot decrease below 2100 unless the slow idle switch is manually activated. The high idle prevents clutch drag with a closed throttle and the slow idle allows complete clutch disengagement with the engine at the idle. This feature would be of value in both cold weather and float operations for obvious reasons.

The cooling fan which incorporates a clutch and free wheel device is assembled in the powerpack by Continental and does not operate at low engine R.P.M. which shortens the warm-up period. Between approximately 2400 and 2600 R.P.M. there is a minor high frequency vibration due to whip of the long tail rotor drive shaft. However, it is only noticeable when passing through this zone.

General flying characteristics are good. The Cessna feels like a heavier machine than it actually is which especially noticeable when reducting speed on approaches. More room is required to kill excess speed if a relatively flat disc is to be maintained. Control is light with good response.

All flying was done at an all up weight of 3260 pounds (gross is 3100) except autorotations which were done at 3000 pounds. At 3260 the aircraft was exceptionally good in pedal turns with a fair breeze of about 10 M.P.H. Only a small amount of peda was required.

At 1500' A.S.L. - temp 45F - wind 8 M.P.H. - several near vertical landings and take-offs were made over trees of about 50' in height. It was necessary to exceed the red line by about 1 1/2" H.G. but with better acquaintance with the aircraft power could be substantially reduced. These take-offs were made at 3100 R.P.M. abd we discovered in the hover checks that the rotor operated most efficiently at 2900 R.P.M. Manifold pressure is redlined at 38 1/2" H.G.

Approximatly 30" H.G. is used for normal cruise and at this weight we indicated 85-90 knots (100 - 105 M.P.H.) Gas consumption (91/98) at cruise is 15 Imperial G.P.H. Performance figures state a cruising speed of 90 - 120 M.P.H. this range being governed by all up weight. A VNE computer is built into the airspeed instrument and when altitude is set against all up weight the red line moves to indicate VNE. Although some application could be made on long hauls it would not be of too much value in our operation. At 3100 pounds and 1500' elevation the red line reads 96 knots (112 M.P.H.) At 2700 pounds and seal level it reads 103 knots (120 M.P.H.)

Retreating blade stall was discussed and Mr. Seibel, the designer of the Cessna, stated that the VNE could be exceeded by about 25 knots before bladde stall would occur. Warning signs before blade stall should be in a progressive manner as follows: loss in R.P.M., feed back into cyclic and an upward pitching of the nose at point of stall.

The aircraft flies reasonably well hands and feet off but in minor turbulence there is typical rotary wing instability.

The following data was obtained from hovering checks: All up weight, 3260 pounds; Elevation, 1500' A.S.L.; Temperature, 45 .; Wind, 12 M.P.H.; H.G. redlined at 38 1/2": (Report then lists manifold pressure required for various heights - final data was 34" H.G. at 345 rotor R.P.M. for a 10 foot hover.)

When revs were lowered in the hover good control was available down to 2300 engine R.P.M. Due to danger of clutch slippage revs were not lowered beyond this point. No violent vibrations were set up but feed backs started to develop in the pedals although there was still anti-torque control in reserve. Power was wound on and this aircraft climbed smoothly on the red line at 2300 revs. Hovering checks indicated greatest efficiency at 2900 engine revs.


Autorotations were done at an all up weight of 3000 pounds - temp 45 - elevation 1500' A.S.L. - wind 10 - 12 M.P.H.

There was good performance in hovering autorotations fromabout 7 feet. A large overall movement of collective is required but very little right pedal. As near as we could tell autorotation characteristics from the air are very similar to the Bell Ranger with an easy rate of descent, good control and an effective flare.


Only minor turbulence was encountered but it appeared that the aircraft would be quite good in turbulent air.

C. of G. was good and little difference was noticed with the rear seats occupied or empty.

Tail rotor clearance is excellent.

Dual pedals are standard and the engineers claim complete installation can be made in 30 minutes.

The noise level is between a G2 and the Ranger. Transmission noise is barely noticeable.

To sum up, the main advantage of a good utility model of the Skyhook, complete with removable rear seats, collapsible internal cargo deck, large cargo door, carriers and hook would be:

1. Versatility - roomy four place or large internal space for bulky cargo.

2. Good flying characteristics and easy to fly.

3. Good performance - 270 H.P. at the driveshaft to 8000' A.S.L.

4. Excellent tail rotor clearnace.

Main disadvantages would be:

1. Visibility - forward visibility is not as bad as expected but some mountain landings or landings on rough rock surfaces would have to be passed up if marginal. However, performance should allow a hover in most spots. Visibility is reasonably good on steep approaches into clearings. Upward visibility is poor for mountain work.

2. Ground clearance to the scoop is 8 1/2" so some care would be necessary on rough terrain.

3. The rotor can droop about shoulder level when slowing down shich is a real hazard. However, droop stops are under consideration.

4. The position of external cargo racks would place the complete load to the rear of the mast. However, a good utility model might necessitate minimum use of external racks as far as freighting is concerned.

The Skyhook will be marketed through the present Cessna dealers and it is quite obvious that it has been designed initially for personnel transport. However, a good utility model could be valuable in parts of our operation, such as patrol work and especially magnetometer surveys - where large internal space is required as well as good range and performance.

Although there are more control and trim devices that required in our work they all appear to be of simple construction and some perhaps could be eliminated in the utility version.

As near as we can guess, performance should level off with the Hiller 12E at about 4-6000 feet and above this altitude, the Cessna should be superior. This takes into account the 3100 pound G.W. as against Hillers 2800.

Factory representatives are anxious to try it out with a hook in the mountains next spring and may be in Vancouver about April.

The Skyhook lists at $79,960.00 U.S. funds.

L.M. Tillotson.

. . . . . . End of Okanagen Helicopters 1960 Skyhook evaluation report.


Thanks to Phil Stehle for the following tales from production.

As one of the people associated with the Skyhook and named in the article, I have some interesting memories of the period it was put into production. Here is a copy of a story I wrote and posted on a Meniere's Disease support forum to which I belong. You have my permission to copy it if you choose.

The light aircraft company (Cessna) I worked for had an itch to get into the helicopter business along with their fixed-wing business. They absorbed a small company that was experimenting with building rotary wing aircraft and had in fact built a few. My department head called me in and assigned me as a manufacturing engineering type to go visit the 'copter design folks and prepare to move toward production .

Full of myself and being somewhat of a smart-ass, I went to the engineering building, found the design leader and Identified myself and my mission,. I proudly proclaimed, "I don't know anything about helicopters except they take off straight up!" That worthy looked me up and down, then replied, "They don't WANT to do that, you have to make them." That was the start of my education in vertical lift machines.

In time, I was the manufacturing go to guy for helicopters. I had a couple of fellows working with me. One was Earl, a cranky old tool maker who had been moved from the tool room to Manufacturing Engineering. He was pretty good at figuring out what kind of tool was needed to build any particular part. I had been promoted from the fixture building shop a few years before because of a decent record of building precision assembly fixtures the size of a small house with good quality, at reasonable labor costs and on schedule. The third member was Dean, a lanky Oklahoman who had been a crackerjack inspector of fixtures as they were built and had worked with me many times.

The three of us took on the task of converting the more or less experimental tooling and planning and converting it to production instruction and tools. We had to work with the designers and they assigned a liaison engineer to work with us to to help get a match between what was in the blueprints and what was built.

Another of the people from the experimental section was the assembly inspector, George, who was very knowledgeable in many aspects of aircraft building rotary or fixed wing. George was a pleasant fellow and took his work seriously. He had one weakness: he tended to get nervous when things went wrong. As a matter of fact, if things went wrong enough George would lose it. He would scream and dart about in a panic. He became well known for this and thus made himself a target for practical jokers of all stripes.

One day George was bent over, leaning into the cabin of a 'copter under construction when he was tricked. One of the assembly mechanics leaned over his shoulder and said, "Damn, I don't feel very good," then dropped a pad of fake rubber vomit next to George's hand. George obliged. He screamed and tried to get away but couldn't because the other was laying on top of him. Everybody had a big laugh. Except, of course, George.

On another occasion I was the perpetrator of a dirty trick on the poor inspector. My partner Dean and I were checking a small piece of the control system that didn't seem to fit. I asked George if could borrow his personal micrometer to check the diameter. Being a good sort he said I could but that his micrometer was in the tool inspection shop for it's periodic required calibration. If I wanted to got get it I was welcome to use it. As I walked away Dean whispered that he had an old junk micrometer in his desk that we could use to fool poor George. I instantly agreed.

After retrieving the good micrometer and taking the measurement, I palmed George's "mike" and dropped the other on the concrete floor. George obliged by screaming and waving his arms. I picked it up, mumbled and apology and threw it at the open drawer of his tool dolly. My aim was accurate, I missed by about an inch and a half. Another set of screams and arm waving. After the laughs at George's expense, we showed him the trick and that his equipment was in perfectly good shape. The classic trick pulled was in the experimental section about the time I got assigned to the project. A couple of the experimental guys were finishing a tail rotor blade just at quitting time. All they had left to do was a row of small rivets along the trailing edge. George decided to inspect it the next morning and left for home. A golden opportunity arose.

After completing the assembly and mounting the blade on the aircraft, they felt it needed embellishment. They went to section of the plant that was building pats of the Giant B-52 and got an extremely large rivet. Back at the helo shop, the riveted two sheets of steel together with the big rivet, then twisted the sheets to shear the thing into just a head and tail. They hollowed out the two parts and, using a dab of rubber cement, stuck the two pieces on the rotor blade to look as if it was made that way. Now it's pretty much standard practice in aircraft that when a rivet has a problem it is drilled out and a slightly larger one installed. This of course, was ridiculously too large. To say it stuck out like a sore thumb is an understatement. It was as if you woke up one morning, looked in the mirror and discovered a preposterously pustulated pimple protruding from your proboscis.

George arrived the next morning and went directly to the aft end of the ship to inspect the tail rotor. Oh yes, you know he once more came through. Screaming and arm waving, he red tagged the whole helicopter so it was to have no work done nor to be moved until the tag was cleared by quality control. George then took off at a dead run to see his boss, the head of quality control. This official was an unpleasant fellow in whom nobody had ever seen the least evidence of a sense of humor.

George, still screaming, practically dragged his boss to the affected area screamed and pointed at the offending assembly. Of course, he didn't know that in his absence, the two jokers had simply reach up and lifted off the fake rivet head and tail. Waving his Arm toward the offending area, He saw a strange look in his boss' eye . He turned his view to the tail rotor rivet and saw - nothing!

In those benighted days video cameras were not a consumer item. Shame. The look George's boss gave him as he considered calling the state mental hospital would have made a a great YouTube.

Please use the FEEDBACK link at left, top if you can add any information, have any corrections, or would like to comment on the Cessna CH-1. I would enjoy hearing from you; if you feel like it, give me a call on my cell 408 828-2810. Special thanks to everyone who has contributed information for this article.

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