History of Gyroplanes

Excerpt From
Autogiro to Gyroplane: 1923 – 2003
Dr. Bruce H. Charnov Ph.D. J.D.
Hofstra University

Juan de la Cierva was born in Murcia, Spain on September 21, 1895, and by 1908-9, had decided to make aviation his career. In 1911 he enrolled at the Civil Engineering College of Madrid (Caminos, Canales y Puertos) and in 1912 with his friends “Pepe” Barcala and Pablo Diaz constructed the first Spanish airplane, the BCD-I, known as “EI Cangrejo” – the “Red Crab”, becoming the “Father of Spanish Aviation.”

In 1919 Cierva produced a large three-engine bomber that, piloted by Captain Julio Rios Argiieso, crashed in its initial flight when the aircraft stalled. Pondering the crash, Cierva’s brilliant insight was to see the wing differently —aircraft stalled when the air passing over the wing failed to generate enough lift at slow speed – he reasoned that stall could be effectively eliminated if the wing itself moved independently of the aircraft. The rotor, a moving, stall-proof wing, was placed on top of a fuselage. He patented the name” Autogiro” and it flew by autorotation, “the process of producing lift with freely-rotating aerofoils by means of the aerodynamic forces resulting from an upward flow of air.” As long as the Autogiro was propelled forward, air coming up through the rotor would generate lift, and should the Autogiro’s motor fail, it would gently descend while air flow upward through the rotor blades.

Between 1920 – 23 Cierva progressively developed autorotation in the C.1, C.2 and C.3, but it would be his forth model that would finally conqueror the air. Cierva stated that the first flight of his CA Autogiro was on January 9, 1923 at Getafe airfield outside Madrid when ( Calvary) Lieutenant Alejandro G6mez Spencer guided the craft in taxi tests during which the craft became airborne. But most historians maintain that the first observed (and filmed) flight of C.4 took place on January 17, 1923 when G6mez Spencer flew 600 ft at a steady height of 13 ft across the field. Transferring operations to England in 1925 and forming Cierva Autogiro Ltd. on March 24,1926 with prominent Scottish industrialist James G. Weir, his brother Viscount William Weir of Eastwood and Sir Robert M. Kindersley, Cierva continued to improve the Autogiro and in early 1929 licensed the technology and rights to his patents to Harold Frederick Pitcairn of Bryn Athyn, P A.

history_clip_image002The youngest son of John Pitcairn, co-founder of Pittsburgh Plate Glass Company, Harold was born in 1897 and took an early interest in aviation. Inspired by the first flight of the Wright brothers in 1903, he began flight training as an air cadet in the last days of WWI, and would eventually earn a pilot’s license signed by Orville Wright. Pitcairn and Agnew Larsen, who he had met in pilot training, produced the classic Mailwing airmail series, but it was the Autogiro that fired their passion. In 1928 Pitcairn ordered a Cierva C.8W (the W was for the American Wright Whirlwind engine), which arrived at Pitcairn Field, Willow Grove, PA and on December 18, 1928 made the first rotary-wing flight in America piloted by Cierva pilot H. C. A. “Dizzy” Rawson, followed the next day by Pitcairn.

In early 1929, Cierva and Pitcairn negotiators agreed that the Pitcairn-Cierva Autogiro Company (PCA) would be formed in America with the rights to license Cierva’s patents. Pitcairn threw himself into the development and promotion of the Autogiro – and the results of the next 16 months would earnhistory_clip_image004 him and his associates the Collier Trophy for the greatest aviation achievement for 1930. Pitcairn had refined Autogiro development, first learning from the C8W (which was presented to the Smithsonian on July 22, 1931), then with a series of developmental aircraft, the PCA-I, 1A and lB. (The PCA-1A is currently exhibited at the American Helicopter Museum & Education Center at the Brandywine Airport, West Chester, PA on loan from the Smithsonian). But it was the next aircraft, the PCA-2, that captivated America. An original design the PCA-2 was seen over major American cities in late 1930-early 1931 in its certification flights to much publicity and acclaim. It innovated with a clutched gearbox that briefly transmitted power to prerotate the rotor to greatly shorten the takeoff run. It would prove a crucial contribution to Autogiro development.

Cierva developed progressively more sophisticated designs with a means to tilt the rotor head and altering the pitch (angle) of each individual rotor blade, called collective and cyclic control, and, making use of Pitcairn’s prerotator, achieved a “jump takeoff” capacity with the C19MkIV in 1931-32 history_clip_image006The rotor would be spun up at zero pitch and then “snapped” into a positive angle, causing the aircraft to “jump” into air, an ability developed by Pitcairn the next year in the developmental PA-22 Autogiro. But both inventors realized that this was only a partial step in realizing the Autogiro’s potential, for a significant problem remained. Even though the Autogiro could takeoff and land vertically, the wing-based control surfaces lost effectiveness at slow landing speeds. Cierva’s C30 series and Pitcairn’s PA-22 and Luscombe-built aluminum body PA-36, and the KD-1 series constructed by Kellett Autogiro Company of Philadelphia were engineering marvels capable of jump take-offs and direct-control without wings. But this came too late to save the Autogiro, for the world’s attention was riveted on the stunning indoor demonstrations of the Focke-Achgelis Fa-61 helicopter by Hanna Reitsch in 1938.

Cierva died in the crash of a KLM DC-2 bound for Amsterdam from the airport at history_clip_image008Croydon Aerodrome, London on December 9, 1936. Stripped of his passion, the Cierva Autogiro Company, under the engineering leadership of Dr. J.A.J. Bennett, would shift the focus of its efforts towards developing a helicopter; and even though Cierva-licensed Autogiros would be used by the British, French, Russian and Japanese forces, the Autogiro would all but disappear by the end of WWII. Few would know or remember that it was the English Cierva Rota C.30A Autogiros that would daily calibrate the coastal radars that enabled the RAF to defeat the German Luftwaffe and win the Battle of Britain. The Japanese Kellett-licensed Kayaba Ka-1A Autogiro series had virtually no impact on the war and the Russian TsAGI A7 Autogyro (not built under a Cierva license, hence not an Augtogiro), the first such aircraft specifically constructed for combat operations, faded before the might of the German onslaught as did the French aircraft built by Liore-et-Oliver and SNCASE.

Almost no one remembers the obscure British Armed Forces Experimental Establishment Malcolm Rotaplane or Rotabuggy, a modified Willys 1/4 ton “four-by-four” military truck with a seesaw “teetering” rotor and attached aircraft control surfaces. Perhaps the most ungainly flying craft ever, it was towed successfully to 1,700 ft. And even less well-known was “Project Skywards”, a parallel wartime attempt in Australia to develop a flying jeep (“Fleep”).

history_clip_image010The most familiar of the WWII autorotational developments were, paradoxically, the most insubstantial, the English and German rotary kites. The Focke-Achgelis FA-330, launched from German submarines at the end of a 400 ft tether to increase target observation, is found in more museums than any other comparable craft only because the Allies captured the factory, but few of the 1943 English Rotachutes designed by Raoul Hafner survive, a one-person giro-glider designed to insert secret agents into occupied Europe from airplanes with a precision gained from use of a two-bladed teetering rotorhead that could be controlled by means of a hanging-stick control.

And so by the end of WWII the Autogiro had effectively disappeared. Pitcairn had surrendered his airfield to the military for wartime use and had the prototype PA-36 aluminum bodies cut up for scrape to aid the war effort. Kellett had renamed itself the Kellett Aircraft Company and what was left of Pitcairn’s manufacturing company, becoming briefly the Firestone Glider & Autogiro Company, was effectively out of the business. The other American licensee, the Buhl Aircraft Company, had developed a single model but failed to survive the Depression. And the attempts by Philadelphias E. Burke Wilford, making use of patents of Germans Walter Rieseler and Walter Kreiser (rigid rotors with control achieved by means of cyclic pitch variation) had not gained engineering acceptance. And perhaps the most intriguing autorotational experiments, the pioneering convertiplane combination of a gyroplane and fixed-wing aircraft of Gerard P. Herrick ended in 1942, but not before successful mid-air conversions by test pilot George Townson in 1937 (that aircraft, the Herrick HV-2A is stored at the Paul Garber Center, Silver Hill, MD). In 1945 Dick Haymes may have crooned to Helen Forrest in I’ll Buy That Dream that “we can honeymoon in Cairo in our brand new Autogiro” but there were no new Autogiros – it seemed certain that Cierva’s vision would merely be a minor footnote to helicopter development, but it did survive — it came down to a single Rotachute and a Russian immigrant – Igor Bensen. Although Harris Woods would design and fly a giro-glider in 1945, a development unknown to Bensen and forgotten by history, the popular future of autorotation lay with the charismatic, passionate Russian!

Igor Bensen, born in 1917, was the son of a Russian agricultural scientist, Basil Mitrophan and Alexandra P. Bensen. His father was posted to Czechoslovakia in 1917 at the beginning of the Russian Revolution while the rest of the family remained behind. The Russian civil war lead to harsh times, and the Bensen family was soon reunited in Prague, far from the turmoil. At 17 Bensen was sent to the University of Louvain in Belgium, from which he received a B.S. degree.vBensen accepted a scholarship from the Stevens Institute in New Jersey in 1937 to study mechanical engineering, graduating with honors in 1940. As an alien Bensen had been forced to turn down a job offer to work for Igor Sikorsky, and his first job was as an engineer with General Electric at the age of 23. General Electric executives took notice of Bensen’s interest and assigned the young engineer to the company’s helicopter development efforts.

While working on the project, Bensen flew a salvaged Kellett XR-3 in 1943, and eventually gained almost exclusive use of the surplus Autogiro. Bensen became a highly skilled Autogiro pilot, and gained a deep understanding of the dynamics and theory of autorotational flight. The USAAF had received some of the recovered FA-330 rotary kites and were experimenting with pilot George Townson, as well as a Hafner Rotachute and Bensen asked his boss to acquire the Rotachute for evaluation. The military agreed to loan the Rotachute providing that General Electric agreed not to fly it.

Bensen ignored the military’s requirements and personally flew the Rotchute in tow, and launched it from the bomb rack of the XR-3. Those tests lead to the Bensen B-1, an amateur-built 120 Ib giro-glider capable of carrying a 300 Ib load, differing from thee Rotachute with the addition of nose and tail wheels, a semi-rigid rotor in place of the Rotachute’s individual flapping rotor blades, and a control stick ‘reverser’ to allow more effective direct-control of the rotor. The crash of the B-1 led directly to the B-2 which was of an all-metal construction. The B-2 lead to the G-E Gyro-Glider in November, 1946 but little came of the G-E model. And subsequently in Schenectady, the Helicraft Equipment Company developed a 60 Ib variant of the Rotachute called the Heli-glider in 1949. An extremely simple design that flew with a 14 ft rotor that achieved 550 rpm, the lack of weight made it difficult to fly with an overhead stick control, and the project was soon abandoned.

Benson, now firmly committed to rotary flight development, joined Kaman Aircraft in 1951 where he organized and directed the research department and flew Air Force and Navy helicopters. After two years, borrowing money from his brother, Bensen left to found his own company in Raleigh, NC.

In 1953 Bensen Aircraft Corporation introduced the B-5 Gyro-Glider, a single-seat rotary–kite towed in back of a vehicle and deriving its lift from an unpowered rotor. It featured a light tubular aluminum frame resembling a cross with two pieces, a longer keel crossed by a shorter perpendicular section. A lightweight aluminum-frame web set was attached to both the keel and a reinforced metal mast extending history_clip_image012upward from the keel. Control was initially achieved with a hanging stick control attached directly to the rotor hub that was positioned on top of the mast with a two-blade rotor. A nose wheel was attached directly to the front of the keel while landing wheels were affixed to each end of the perpendicular crosspiece. The keel, in back of he seat and mast, carried a plywood fin and rudder much as had the Rotachute. It flew well when towed by even a small automobile and did not require any license, and was relatively safe. It was also distinguished by ease of construction and the builder could either purchase a kit or build from plans. The materials were readily obtained and fabrication could be completed by the moderately skilled in 3-4 weeks. It would become the home-built B-6, and the prototype was accepted into the Smithsonian’s NASM on July 22, 1965.

Bensen subsequently developed a Reynolds aluminum prototype, the B-7 Gyro-gilder which flew on June 17, 1955. From B-7 .came the B-7M (for motorized) which first flew on December 6,1955 with Bensen as pilot and Charles “Charlie” Elrod and Tim Johnson as ground crew. It weighed 188 lb. as the airframe was made of rounded aluminum tubing and had a wooden propeller attached to a 42 hp Nelson two-stroke engine, with the wooden rotor attached to a spindle type tilting head cyclic pitch rotor with a hanging control stick. Bensen called his Rotachute-derived creation a Gyrocopter, a term he subsequently trademarked. After three days of successful flight testing the B-7M crashed as its pressurized fuel tank failed. Bensen, a highly experienced Autogiro pilot, set the aircraft down in woods adjacent to his NC factory. He later ascribed the safe landing to “much luck and the good Lord’s will.” The B-7M, rebuilt in three days, was flying by December 17, 1955, a particularly moving experience for Benson as that was the 52nd anniversary of the Wright brothers first powered flight.. Ever aeronautical engineer and pragmatic scientist, Bensen relentlessly analyzed the flight performance of the B-7M, particularly those factors that had led to the accident, and the result was an improved control linkage to the rotor head.

The subsequent B-8M model, incorporating the improvements developed and tested in the B-7M, powered by a more powerful 72 hp McCulloch two-stroke piston engine that had been used on drones for the military, was placed into production in 1957 and became the most produced and copied aircraft design in history and provided, history_clip_image014in kit form and plan-built, the most popular way to fly. The “Spirit of Kitty Hawk”, a B-8M Gyrocopter in which Bensen had personally duplicated the Wright brothers historic first flight at Kitty Hawk on December 17, 1966, and with which he had set twelve world and national Gyrocopter speed, distance and altitude records between May 1967 and June 1968, was accepted into the Smithsonian Institution aviation collection on May 14, 1969. The Bensen, and its variants and local adaptation was to dominate the American Gyrocopter movement for almost twenty-five years.

In Europe, however, it was a different story. England’s Wing Commander history_clip_image016Kenneth H. Wallis, Scotland’s Jim Montgomerie in and Finland’s Jukka Tervamaki began with Bensen kits or plans, but soon modified the design, taking gyrocopter design into some very un-Bensen-like directions. Wallis, who would achieve international fame with “Little Nellie”, a WA-116 autogyro, in the 1967 James Bond film You Only Live Twice, remains an honored pilot, world record holder and designer, while Tervamaki did pioneering work with composite materials (fuselage and rotor blades) and was the most significant influence on Italy’s premier designer/ manufacturer Vittorio Magni.

history_clip_image018But all mid-century-on attempts to revive the Autogiro failed – in 1959-60 Kellett attempted bring its aircraft back for agricultural uses to no avail, and the Pitcairn license of its 1936 AC-35 “Rotadable” Autogiro, capable of driving down the highway at 25-30 mph (stored today at the NASM Paul Garber facility) by Indiana’s Skyway Engineering got no further than a prototype in the early 1960s. The most ambitious realization of Cierva’s vision, the Fairey Rotodye produced under the initial direction of Dr. J.A.J. Bennett and Captain A.Graham Forsyth, flew between 1957 -1962 history_clip_image020until cancelled by the British government in its “rationalization of the helicopter industry”. The Rotodyne, a convertiplane making use of four 50 ft steel jet-tipped rotors, could take off and land as a helicopter and fly as a gyroplane carrying 42 persons at 200 mph – in 1957 with a perfect safety record. In order to conceal the amount of its funding, the only model was ordered destroyed by the British government and all that remains of this incredible aircraft are a few parts in a museum, photographs and films – had it gone into production and the USMC pursued its interest, the military might have acquired an effective vertical/ fixed-wing combination that even now J2_000remains unrealized. And the Kamov Ka-22 (The “Russian Rotodyne”), known in the Soviet Union as the Vintokrulya (Vintokryl) (“Screw Wing”), and dubbed “Hoop” by NATO, also failed to gain government acceptance after several crashes. And the Umbaugh (later Air & Space) 18A, Avian 2/180 and McCulloch J-2 2/3 place gyroplanes failed to achieve commercial acceptance despite technical sophistication and the enthusiastic belief of their backers that the world needed a gyroplane. In general, all that remained of Cierva and Pitcairn’s autorotational vision were the thousands of amateur-built Gyrocopters and their variants.

Bensen and his associates would in 1962 found the Popular Rotorcraft Association (PRA), which even today remains the world’s preeminent Autogiro / auto gyro / Gyrocopter / gyroplane organization. Bensen declared in 1970 somewhat unfairly that Ken Brock had so modified the design that it could not no longer be called a Gyrocopter – Brock then called his KB2 a “gyroplane.” Under Brock’s presidency of the PRA (1972 -1987) gyroplane design flourished. The most notable of the new designers was Californian Martin Hollmann. His major contributions include the Sportster, the world’s first successful two-seat amateur-built gyroplane trainer in 1972, and the first “ultralight” gyro plane, the “Bumble Bee”, in 1983. Also significant was Bill Parsons two-seat Trainer, a Bensen B-8M with a longer keel to accommodate a second seat, dual controls and a rotor head attached by an upside-down “u” shaped tandem double mast. But it was only at the start of a new century that the Autogiro was to become the gyroplane.

Groen Brothers Aviation [now GAC], headed by brothers David and Jay Groen, has developed a family of larger Hawk 4 gyroplanes targeted to the agricultural, law enforcement, package delivery and passenger shuttle service markets. Time magazine, in its November 19, 2001 issue, named the Hawk 4 as one of the best “Inventions of the Year.”

The Utah Olympic Public Safety Command (UOPSC) made use of a Hawk 4 during the history_clip_image0242002 Olympics with a FLIR Systems, Inc. day / night observation system, a Spectrolab Inc. SX-5 search light, an Avalex Technologies flat panel display, a Broadcast Microwave Services realtime video downlink system and a law enforcement communications radio stack. GBA [now GAC] had succeeded in defining a reconnaissance mission where Cierva, Pitcairn, Kellett, the French, English, Germans, Russians, Japanese and even Ken Wallis had failed. Given the enthusiastic reception of the Hawk series of gyroplanes, the business acumen of the Groen brothers and their associates, it is likely that they will be successful and the Autogiro, in its newest gyroplane configurations, will achieve an acceptance that has been elusive since the PCA-2 and C.30A flew over American and European skies.

General Aeronautics Corporation extends their gratitude to

Dr. Bruce H. Charnov for permission to share

the preceding excerpt from his informative

book From Autogiro to Gyroplane (2003).