Well over a half-century ago. 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.

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!).

Design and construction started on the little known but record setting Cessna CH-1 helicopter over 50 years ago 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 over forty 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. . ."

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, Chief Test Pilot, 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.

Charlie decided to leave Bell in the fall of 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.

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, only one of whom was licensed as a rotary wing pilot. 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.

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.

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.

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.

The artist's drawing shown above was the origin of the 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. Ten Eyck reconfigured the fuselage to the final shape. He also later helped shape the master plaster mold for the fuselage and cowling. Unlike so many 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-Flôr 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?

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.

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 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.

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.

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".

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.

"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."

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. 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 and later, in the Spring, replaced by Jack Leonard who came from Goodyear.

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) 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. 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.

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."

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.

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, 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.

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!

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.

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).

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.

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.

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 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.

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.

The suction pump for the flying system was a Cessna-designed rotary vane (six) type positive displacement pump driven 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.

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.

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.

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 Cessna 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.

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. 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.

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 Army evaluation tests did not result in any further military contracts. The details of the Army's use of the YH-41 and reports 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.

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.

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 two 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 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.

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.

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. 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. Another photo showed 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 as Bowman made his landing ( video available from the American Helicopter Society). 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!

No 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."

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.

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 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.

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.

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.

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".

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."

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.

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."

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 practive however as military helicopter instrument training was all conducted in helicopters that couldn't meet civil standards as the CH-1C did.

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.

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.

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.

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 11so were there more?). Of interest, some of the MAP helicopters were delivered by Cessna in 1963 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. Reportedly, four Cessnas were delivered to Ecuadorian armed forces; who knows, maybe there is a Cessna helicopter hulk on some schoolyard playgound in Guayaquil or on some slope high in the Ecuadorean Andes! Some ships (three? - or more?) 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 but it is not confirmed. 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.

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.

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.

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?