1940 ? 2010: Brief history of hybrid helicopters around ... - Eurocopter

1940 – 2010: Brief history of hybrid helicopters 

around the world 

A visionary: Gustave de Ponton d'Amécourt 

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In 1863, through his work entitled "La Conquête de l’Air par l’Hélice, exposé d’un nouveau 

système d’Aviation", Gustave de Ponton d’Amécourt invented the concept of the helicopter 

which was inexistent until then. This "spiral wing" aircraft is equipped with a horizontal rotary 

wing "which lifts weight by cutting the air at an angle with paddles". 

He opposed the concept of the helicopter and the concept of the orthopter (which lifts weight 

by pressing down on the air), or in other words, the airplane. 

Gustave de Ponton d’Amécourt conceptualized the need to counter the torque generated by 

the horizontal rotor, driven by an engine, and invented an architecture with two counterrotating 

rotors. 

Another interesting notion he tackled was the notion of two means of forward propulsion: 

vertical and short takeoff and landing (VSTOL). 

This concept is explained by its inventor: 

"Do you want a propulsion process? Here is the first one I thought of: you put a third rotor at 

the front of the aircraft, in the vertical plane, i.e. perpendicular to the other two; you spin this 

rotor and each turn it makes moves the aircraft forwards by the length of its pitch ... this 

process is not the best nor the most simple; here is another: simply set the axis of the two lift 

rotors at an angle relative to the weight of the aircraft".

Part 1: The Concept 

According to Professor J. Gordon Leischman: "A hybrid helicopter implies the use of a wing 

(hybridized lift) or the addition of a separate source of thrust for propulsion (hybridized 

thrust). The aim is to relieve the rotor of its normal lift and propulsion functions. This can be 

achieved by using a wing and/or auxiliary propulsion." 

Combining hover and high-speed horizontal flight capabilities is an old dream of airplane and 

helicopter designers. To cover the whole flight spectrum and all the missions of different 

aircraft with the same flying machine is one of the aeronautical industry's biggest challenges. 

Part 2: The Context 

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At the end of the Second World War, aircraft manufacturers threw themselves into the hybrid 

adventure. Between the 1950s and the 1970s, the Western world and the former Eastern 

Block saw the emergence of a large number of technological demonstrators aimed at 

combining vertical flight and speed. 

Only three categories have managed to put an operational aircraft into service: the 

convertible category with the Bell- Boeing V22, the vectored thrust category airplane with the 

Harrier and its derivatives in Western Europe, and the additional vertical thrust category 

airplane with the YAK38 in the ex-Soviet Union. 

Discover a panorama of forty-five VSTOL concepts that were experimented between 1954 

and 1990 on the www.vtol.org website, including many experimental aircraft, the famous X- 

Planes. 

Part 3: The Concept 

During the cold war period, the Soviet Union was the leader in terms of aeronautics and in 

particular regarding new concepts. However, Europe did not remain totally absent from this 

market, notably in the field of jet airplanes where many concepts were produced: the C400 

Avatar Volant, the C450 Coleopter, the Dornier DO31, etc. 

From 1950 to 1970, during this search for speed for VTOL, the tilt rotor (rotary wing) 

convertible aircraft triumphed from this competition. 

Whereas the autogyro (a rotary wing aircraft where the rotor is never driven) which had its 

hour of glory between the 1st and 2nd world wars thanks to the pilot Juan de la Cierva, was 

ousted because it did not allow hover flight.

But personalities such as Juan de la Cierva in Europe or Harold Pitcairn in the USA, 

contributed to technical progress thanks to their inventiveness. 

Part 4: Models Developed Throughout the World 


1938 FL-185: Anton Flettner, Germany 

• 12-meter-diameter 3-bladed rotor, driven in hover flight then operating as an 

autogyro in forward flight 

• Two propellers back to front on the end of an arm, providing anti-torque in hover 

flight and propulsion in forward flight 

• 140 hp (104 kW) Siemens-Halske 14A engine 

• Maximum weight: 900 kg


1945 WNF 341V4: Freidrich von Doblhoff (Wierner Neustader Flugzeugwerke), Austria 

• 10-meter-diameter rotor driven by blade tip jets (air/fuel mixture) which does not 

require anti-torque 

• Pusher propeller at the rear which was only ground tested; the propeller shown 

on the V3 & V4 models creates an airflow for flight control over the tail yaw control 

surfaces 

• 140 hp (104 kW) BMW-Bramo Sh 14A engine 

• Maximum weight: 640 kg 

• At the end of the war, the V4 and von Doblhoff embarked for the USA where von 

Doblhoff participated actively in the McDonnell XV-1; a member of his team, 

Theodor Laufner, headed to France to participate in the development of the SO 

1221 Djinn "cold" jet rotor drive. Finally, August Stepan, another engineer from 

the von Doblhoff team, but also a WNF342 pilot, joined Fairey Aviation in Great 

Britain to develop a jet rotor on the Jet-Gyrodyne and the Rotodyne.


1947-1949 Gyrodyne: Fairey, Great Britain 

• Sixteen-meter-diameter driven rotor operating with a low collective pitch without 

reaching the autogyro mode 

• One pusher propeller on the right 

• 5.08-meter-span wing 

• Maiden flight on the Fairey airfield at White Waltham on December 7, 1947, at 

the hands of Squadron Leader Basil Arkell 

• Powered by a 520 hp (388 kW) 9-radial-cylinder Alvis Leonides engine 

• Maximum weight: 2180 kg 

• World speed record over 3 km on June 28, 1948, with a speed of 108 kt


1949 CGA -2a: Gyrodyne, Gyrodyne Company of America USA 

• First compound helicopter to fly in the USA 

• Two coaxial two-bladed rotors driven by a 450 hp Pratt & Whitney R-985 piston 

engine 

• Two pusher propellers each driven by a 100 hp Continental piston engine, and 

providing yaw control


1953 SNCASO FARFADET France 

• 11.2-meter-diameter three-bladed rotor driven by blade tip jets (air/fuel mixture) at low 

speeds, then autogyro operation 

• Constant-speed Ratier two-bladed pusher propeller mounted at the front 

• Powerplant: for the rotor, a 275 hp (202 kW) Arius I turbocharger located behind the 

cabin supplied the compressed air; for the propeller, a 275 hp (202 kW) Artouste II 

turbo-prop engine 

• Turbo-prop engine gas deflection valves for yaw control, mounted at the end of the 

tail 


• Maximum weight: 1,500 kg 

• Maiden flight on the Villacoublay airfield on May 7, 1953, at the hands of Jean 

Dabos.


1954-1956 Jet-Gyrodyne: Fairey, Great Britain 

• Second prototype of the Gyrodyne modified to incorporate a rotor driven by blade tip 

jets (air/fuel mixture) and demonstrator for the future Rotodyne 

• Two 3250 hp (2300 kW) Napier Eland E.L turbo-shaft engines driving the pusher 

propellers and two compressors supplying compressed air to the blades. 

• 14.2-meter-span wing. 

• Maximum weight: 14,900 kg. 

• Maiden flight on November 6, 1957, at the hands of Ron Gellatly and John Morton. 

• World speed record for convertibles, reaching 167 kt on a 100 km circuit on January 

5, 1959.


1954-1957 McDonnell XV-1: McDonnell, USA 

• 9.4-meter-diameter three-bladed rotor driven by blade tip jets (air/fuel mixture), 

operating as an autogyro in forward flight 

• Two-bladed pusher propeller located behind the fuselage 

• Two small tail rotors which ensure yaw control at low speed 

• 550 hp (405 kW) R-975-19 Continental piston engine driving the pusher propeller 

and two compressors which supply compressed air to the blades 


• Maiden flight on July 14, 1954 

• First rotary wing aircraft to reach 200 mph (173 kt) on October 10, 1956

All rights Reserved Acknowledge to Agusta Westland 

1957-1962 Rotodyne Y model: Fairey then Westland, Great Britain 

• Demonstrator for the Rotodyne Z model, designed to carry 57 to 70 passengers 

and with a maximum weight of 31,000 kg 

• 27.5-meter-diameter four-bladed rotor driven by blade tip jets (air/fuel mixture), 

operating as an autogyro in forward flight 

• Two four-bladed pusher propellers with variable pitch, also providing yaw control 

at low speed 

• Two 3,250 hp (2,300 kW) Napier Eland E.L. turbo-shaft engines driving the 

pusher propellers and two compressors supplying compressed air to the blades 



• Maiden flight on November 6, 1957, at the hands of Ron Gellatly and John Morton 

• World speed record for convertibles, reaching 167 kt on a 100 km circuit on 

January 5, 1959.


1961 KA-22 Vintokryl: Kamov, USSR 

• Two 22.5-meter-diameter four-bladed wing tip rotors 

• Two four-bladed pusher propellers mounted on the wing tips 

• Two 6,500 hp (4,800 kW) Soloviev D-25VK turbo-shaft engines, pod mounted on the 

wing tips, driving the rotors and the pusher propellers 

• 25-meter-span wing 

• Maximum weight: unknown, aircraft capable of carrying 80 passengers or a 16,500 kg 

payload 

• Maiden flight: April 1960 

• World speed record over a 15 - 25 km circuit on October 7, 1961: 192 kt


1962-1969: Bell 533 model: Bell Helicopter Company, USA 

• Research helicopter developed on the basis of a Bell YH-40 which is equipped 

with various rotors (approximately 13-meter-diameter two-bladed, three-bladed 

and four-bladed rotors), with an auxiliary propulsion and/or a wing 

• 1400 shp (1030 kW) Lycoming T53-L-13 turbo-shaft engine driving the rotor 

• In the auxiliary propulsion versions: use of two 420 daN thrust Continental J69-T- 

9 jet engines, then two 770 daN thrust J69-T-29 jet engines and finally two 1500 

daN thrust Pratt & Whitney jet engines 

• In the winged version: addition of an 8-meter-span wing 

• Maiden flight on August 10, 1962 

• Reached a speed of 275 kt on April 15, 1969


1962 – 1966 Piasecki 16 H- 1 Pathfinder: Piasecki Aircraft Corporation, USA 

• 12.5-meter-diameter three-bladed rotor 

• 1.7-meter-diameter shrouded three-bladed pusher propeller equipped with the "Ring 

Tail" system, providing anti-torque, fore-and-aft pitch and yaw control through 

propeller thrust deflection 

• One 550 hp (405 kW) United Aircraft of Canada PT6B-2 turbo-shaft engine, driving 

the rotor and the shrouded propeller 

• Maiden flight: February 21, 1962 

• Speed attained: 170 mph/275 km/h


1963-1965 Kaman UH-2 Compound: Kaman, USA 

• Research aircraft comprising a Kaman Seasprite UH-2A single-engine aircraft 

with an additional auxiliary jet engine and/or a wing 

• Rotor and rotor drive: standard UH-2A (13-meter-diameter four-bladed rotor and 

1,500 shp (1,100 kW) General Electric T58-8F turbo-shaft engine) 

• General Electric YJ85, pod mounted on the right, with approximately 1,100 daN of 

thrust 


• Maiden flight: November 26, 1963


1964 Lockheed XH-51A Compound: Lockheed, USA 

• Demonstrator for a compound helicopter obtained from two XH-51As (No. 

151263) equipped with a wing and a jet engine 

• 10.7-meter-diameter gyroscopic rigid four-bladed rotor from the original XH-51A 

• 1.8-meter-diameter tail rotor 

• 375 kW Pratt & Whitney PT6B-9 turbo-shaft engine for the rotor drive 

• 1180 daN thrust Pratt & Whitney J60-P-2 jet engine for the additional propulsion 



• Maiden flight: April 10, 1965 

• Unofficial record for a helicopter on June 19, 1967: 263 kt

1964 NAGLER VG-1 VERTIGO: Napier Helicopter Company, USA 

• Wingless fuselage of a Piper Colt to which a Sud-Aviation Djinn helicopter rotor is 

added ("cold" jet drive). 

• Standard Piper Colt propeller at the front. 

• 108 hp (80 kW) Piper Colt standard Lycoming piston engine for the propeller drive, 

and a Garett turbocompressor for the rotor compressed air supply. 

• Low speed yaw control provided by blowing the compressor jets at the vertical fin. 

• Maiden flight in January 1964. 


1965-1966 VFW H2: Vereinigte Flugtechnische Werke, Germany 

• Demonstrator aircraft for the VFW H3-E 

• 6-meter-diameter two-bladed rotor, driven by blade tip jets through combustion of 

an air/fuel mixture in hover flight, and by "cold" jet (only compressed air) in 

forward flight 

• Pusher propeller behind the pilot 

• 72 hp (53 kW) Mc Culloch piston engine driving the pusher propeller and the air 

compressor for the rotor 

• Maximum weight: 270 kg

• Maiden flight: April 30, 1965 

• The H3-E model with the fuselage and cabin capable of carrying one pilot and two 

passengers did not fly in the compound version, the two shrouded propellers 

installed on the sides of the fuselage were never installed for flight. 


1965-1967 NH-3A compound 61F: Sikorsky, USA 

• Research aircraft developed on the basis of a Sikorsky SH-3A Sea king, with the 

fuselage modified to make it more aerodynamic by removing the fairing and floats 

and adding auxiliary jet engines and/or a wing 

• 19-meter-diameter five- or six-bladed rotor 

• Two 1250 shp (920 kW) General Electric T59-GE-8Bs for main rotor and tail rotor 

drive 

• Two 1300 daN thrust Pratt & Whitney J-60P-2 jet engines for the auxiliary 

propulsion 



• Maiden flight: May 21, 1965


1967-1972 AH56-A Cheyenne: Lockheed, USA 

• Ten development prototypes were manufactured for a two-crew attack helicopter 

for the US Army 

• 15.6-meter-diameter Lockheed gyroscopic rigid four-bladed rotor 

• 3-meter-diameter four-bladed tail rotor 

• 3-meter-diameter Hamilton-Standard three-bladed pusher propeller 


• 2,500 kW General Electric T64-GE-16 turbo-shaft engine for rotor and pusher 

propeller drive 

• Maiden flight on September 21, 1967, at the hands of Don Segner 

• The Cheyenne was the compound helicopter which came the closest to being put 

into service. When the program was stopped on August 9, 1972, the Cheyenne 

had reached a speed of 215 kt. Its high-speed maneuverability was remarkable 

and especially it had an exceptional weapons system for the period; the 

forerunner of the weapons systems on modern helicopters such as the AH64 

Apache or the Tiger.

1975 BO105 HGH: MBB, Germany 

• Research aircraft for studying high speeds, produced on the basis of a BO105 by 

adding fairings on the rotor head and at the rear of the fuselage, and by reducing 

the height of the landing gear and adding a wing 

• 9.8-meter-diameter AGBI rigid four-bladed rotor 

• BO150 standard tail rotor with 6-meter-span wing 

• Aircraft reached 220 kt 

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1975-1977 Gazelle SA349 Z: Aérospatiale, France 

• Research aircraft produced on the basis of a Gazelle SA342, equipped with a 

wing in order to study the increased maneuverability provided by the wing 

• 10.5-meter-diameter Gazelle standard three-bladed rotor 

• First helicopter equipped with the Fenestron fan-in-fin anti-torque rotor 

• 640 kW Astazou XIV M turbo-shaft engine driving the main rotor and the 

Fenestron


1978-1988 RSRA: Sikorsky, USA 

• Research aircraft used to study different types of rotors (Rotor System Research 

Aircraft) and equipped with a wing and additional propulsion 

• S-61 five-bladed standard rotor 

• S-61 standard tail rotor 


• Two 1040 kW General Electric T58-GE-5 turbo-shaft engines 

• Two 4400 daN thrust General Electric TF34-GE-400A jet engines for the 

propulsion 

• Maiden flight of the compound version on April 10, 1978 

• The S-72 RSRA is one of the few compound helicopters that was not made in 

view of high speeds


1978-1980 XH-59A: Sikorsky, USA 

• XH-59A (Sikorsky S69) demonstrator, manufactured to study the ABC (Advancing 

Blade Concept) rotor which, in its compound version, was equipped with 

additional jet engines 

• Two 12-meter-diameter ABC rigid counter-rotating rotors 

• Two 1400 kW Pratt & Whitney PT-6T-3 TwinPack turbo-shaft engines 

• Two 1300 daN thrust Pratt & Whitney J60-P-3A jet engines for the propulsion 

• Maiden flight: end of 1978


2007 XH-49A SpeedHawk: Piasecki (based on the Sikorsky SeaHawk), USA 

• Technological demonstrator for the VTDP (Vectored Thrust Ducted Propeller) 

concept, modern version of the Ring Tail which flew on the Piasecki 16H 

Pathfinders I and II. Designed on the basis of a Sikorsky YSH-60 Seahawk, 

equipped with a wing and a ducted propeller with vectored thrust 

• 16.4-meter-diameter SeaHawk standard rotor. 

• MT five-bladed propeller - Vectored Thrust Ducted Propeller providing anti-torque, 

propulsion, yaw control and fore-and-aft pitch balance 

• Piper Aerostar wing with a span reduced to approximately 9 meters 

• Two 1250 kW General Electric T700 turbo-shaft engines from the SeaHawk, 

driving the rotor and the VTDP; in phase II of the program it was scheduled to add 

a third turbo-shaft engine (440 kW Rolls Royce 250C30) dedicated to propulsion 


• Maiden flight on June 29, 2007, at the hands of S. Schellberg


2008 X2: Sikorsky, USA 

• Technological demonstrator for the Sikorsky ABC rotor, subsequent to the XH- 

59A 

• Two 8-meter-diameter ABC counter-rotating four-bladed rotors 

• One six-bladed pusher propeller 

• One 1340 kW LHTEC T-800 turbo-shaft engine, driving the rotors and the pusher 

propeller 


• Maiden flight on August 27, 2008, at the hands of K. Bredenbeck 

• On September 15, 2010, the X2 reached a speed of 250 kt.

1940 ? 2010: Brief history of hybrid helicopters around ... - Eurocopter

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