30. EWR VJ101C
The supersonic VJ 101C, built by the German EWR ("Consortium") of Messerschmitt, Heinkel and Bölkow, employed a lift plus lift/cruise propulsion concept, powered by six Rolls-Royce/MTU RB.145 turbojet engines. Two of these engines were mounted in tandem aft of the cockpit; the other four engines were in pairs in wingtip swivelling nacelles. On the second of the two experimental aircraft, the VJ 101C X2, the wingtip mounted engines were equipped with afterburners which increased their available thrust from 2,750 to 3,650 pounds each. The first VJ 101C hovering flight occurred on 10 April 1963, and the first horizontal takeoff was accomplished on 31 August 1963. A double transition (vertical takeoff through conventional flight followed by a vertical landing) was achieved on the sixth flight on 20 September 1963. The non-afterburning X1 became the world's first supersonic V/STOL aircraft in July 1964 when it broke the sound barrier in a shallow dive. This aircraft was lost in an accident on 14 September 1964. This occurred when the aircraft became uncontrollable immediately after a horizontal takeoff. The pilot ejected at an altitude of ten feet during an uncommanded roll. He survived but suffered crushed vertebrae. The accident was found to have been caused by a roll-rate gyro which had been installed with reversed polarity. Prior to its loss, the VJ 101C X1 had completed 40 aerodynamic flights, 14 full transition flights and the Hannover Air Show presentation on 3 May 1964. The VJ 101C X2 flew its first hovering free flights on 12 June but did not attempt to use its afterburning capabilities for vertical takeoffs until 10 October 1964; within two weeks, the VJ 101C X2 demonstrated complete transitions from vertical to horizontal flight and back to a vertical landing using afterburning. It suffered from high temperature and erosion issues, and crashed when it ingested hot exhaust gases and suffered a significant thrust loss while attempting to land on an elevated platform. The rotating nacelle design was abandoned, and the proposed follow-on, the VJ 101D, dispensed with the wingtip-mounted engines but retained the lift plus lift/cruise propulsion concept. Its use of RB.162 five lift engines and two aft fuselage RB.153 lift/cruise engines (with internal thrust deflectors) was very complex and the VJ 101D was canceled after engine testing had begun.
31. Dornier Do 31
The German Dornier Do 31 project was begun in the early 1960s as a 50,000 lb gross weight vertical take-off and landing military transport plane, capable of lifting 6,000-8,000 lb. It was 68 ft long, with a two pilot crew sitting side by side. It could load 1,470 cubic ft of cargo through the rear loading ramp. It used two 15,500 lb thrust Bristol Pegasus 5-2 engines and eight 4,400 lb thrust Rolls-Royce RB.162-4D engines. The powerplants were divided into four wing-mounted pods - a Pegasus pod and a pod of four lift engines on either side of the fuselage. The lift engine pods were located at the ends of the 59 ft span wing. The lift engine exhaust could be vectored backward or forward 15° for take-off and landing, respectively. The Pegasus could vector exhaust from 30° forward to 80° back. Differential vectoring and thrust levels were used for control in roll and yaw; pitch was affected by a puffer jet in the tail. After almost four years of hover rig tests of increasing size and realism to develop the autostabilization controls, three Do 31 aircraft were built: one each for conventional flight trials, ground testing, and hover and transition research. The first aircraft made a conventional flight without the lift engine pods on 10 February 1967. The third aircraft made the first hover on 22 November 1967. First transition from vertical was on 16 December, and first transition to vertical 6 days later. It continued to fly until it was canceled in April 1970: the large drag and weight of the engine pods reduced the useful payload and range compared to contemporary conventional transports.
32. Lockheed XV-4B Hummingbird II
In 1964, when the XV-4A (#38) proved unsatisfactory, the remaining Hummingbird was modified with four General Electric J85-GE-19 lift engines (3,000 lb thrust) for hover. Two additional J85 engines provided thrust during horizontal flight. During hover, large diverter valves directed the cruise engine exhaust on each side through the fuselage to a nozzle between the lift engines for additional vertcal thrust. In transition, one lift/cruise engine was diverted, while the other provided forward thrust. Pitch and yaw jets at the nose and tail provided control in hover. Maximum vertical take-off weight was 12,600 lb. The Hummingbird II had a fly-by-wire dual channel autostabilization system. It was rolled out on 4 June 1968 but was destroyed in a crash during a conventional flight on 14 March 1969, without ever making a hover.
33. VFW VAK 191B
The VAK 191B used two Rolls-Royce/MTU RB.162-81 lift engines (6,000 lb thrust each), one mounted directly behind the cockpit and one aft of the wing, plus a MTU/Rolls-Royce RB.193-12 vectored thrust turbofan engine (10,163 lb thrust) mounted between them. The RB.193 was a scaled down version of the Roll Royce Pegasus engine used on the Kestrel/Harrier. First untethered hovering flight of the German/Italian VAK 191B was conducted on 10 September 1971, with first transition achieved on 26 October 1972. The program was intended to develop a high-speed V/STOL strike aircraft; but it was canceled due to a change in NATO strategy. The US Navy subsequently funded additional V/STOL oriented flight tests.
34. Yakovlev Yak-38 Forger
The Yak-38 Forger used two in-line Rybinsk RD-36-35FVR lift engines (6,722 lb thrust each) immediately behind the cockpit inclined with the engine exhaust at 13 rearward. One Soyuz Tumanskiy/Khatchaturov R-27V-300 turbojet (13,444 lb thrust) was mounted in the center fuselage and exhausted through two hydraulically actuated vectoring nozzles (connected by a transverse shaft), one on each side of the fuselage just aft of the trailing edge of the wing. The first prototype flew in 1971 and the Yak-38 (originally designated the Yak-36M) first appeared to the West in July 1976 when the Kiev deployed with a developmental squadron of Forger-As and traveled through the Mediterranean. The normal complement for the Kiev-class through deck aircraft carrier was a dozen single-seat Forger-As and one or two twin-seat trainer Yak-38U Forger-Bs. The primary roles were fleet defense (particularly against shadowing maritime surveillance aircraft), reconnaissance, and anti-ship strike, but was never used in combat. The Forger was removed from front line service in 1992-93, although a few remained in the inventory for another year as limited proficiency training aircraft. A total of 231 aircraft had been built by the time production ended in 1988.
35. Yakovlev Yak-141 Freestyle
The Yak-41 program was initiated in 1975, about the same time that the Yak-38 was first being deployed. The supersonic Freestyle was optimized for air defense with an attack capability as a secondary role. The first conventional flight was made on 9 March 1987 and the first hover on 29 December 1989. The first official details were not released by the Soviet Union until the 1991 Paris Air Show (re-designated as the Yak-141) by which time the two flying prototypes had accumulated about 210 hours in the air. A dozen FAI-recognized Class H. III records for V/STOL were set in April 1991, consisting of altitudes and times to altitudes with loads. In flight testing, the Freestyle achieved a maximum speed of 1.7 Mach, and maneuverability was repeatedly claimed to be almost as good as that of the MiG-29 Fulcrum (although the small wings of the Freestyle make this extremely doubtful). Flight testing was originally intended to continue until 1995, but development was stopped in August 1991 due to the shrinking Soviet military budget. Yakovlev funded the development from its own resources for a while, in the hopes of attracting a foreign investor. The second flight prototype was destroyed after a hard landing on the Admiral Gorshkov aircraft carrier on 5 October 1991. The following year, the surviving prototype was demonstrated at the Farnborough Air Show, but the design bureau was still unable to find a market for the design. Tip Jets: A compound autogyro transmits full power to the rotor for vertical flight, and transfers power to a horizontal propulsion device for forward flight with wings providing lift to allow the aircraft to fly faster than a conventional helicopter. Tip Jet aircraft pump fuel and compressed air to small burner chambers at the rotor tips. This combustion generates thrust which turns the rotor.
36. McDonnell XV-1
McDonnell's tip jet autogyro, the XV-1, was powered by a single 550 hp Continental R-975-19 nine-cylinder radial piston engine. It drove two air compressors to power the 31 ft three-bladed rotor for vertical lift, and powered a 6 ft diameter two-bladed propeller mounted at the rear of the fuselage for forward flight. A small rotor at the end of each tail boom provided yaw control. Overall length was 50 ft, with a 26 ft wingspan. Empty weight was 4,300 lb which increased to a maximum gross weight of 5,500 lb. First tether test was in 1954, with the first free flight on 11 February of that year. First transition to horizontal flight was on 29 April 1954. The second of the two aircraft was damaged in autorotation testing in December 1954. On 10 October 1955, the XV-1 exceeded contemporary rotor-wing speed records by hitting 200 mph. With conventional helicopters improving their cruise speeds, however, the program was canceled in 1957.
37. Fairey Rotodyne
The British company Fairey had built several compound helicopters in the 1940s. One of these was modified with tip jets as the Jet Gyrodyne in 1953. Based on this data, Fairey designed the 33,000 lb Rotodyne, a 40 passenger transport powered by two 2,800 shp Napier Eland 3 turbine engines. The fuselage was 59 ft long with nearly 3,300 cubic feet of internal volume, ending in rear clamshell loading doors. The 60 ft diameter four-bladed rotor was rotated by tip-jets in vertical flight and autorotated in cruise, providing about half of the aerodynamic lift. During transition, the engine power was transferred by hydraulic clutches to two four-bladed tractor propellers mid-mounted on the 46 ft wide wings. In hover and forward flight, yaw was controlled by differential propeller pitch, while pitch and roll were produced by the cyclic rotor pitch. Aerodynamic surfaces augmented control in forward flight. First flight in helicopter mode was on 6 November 1957. The first transitions were begun in April 1958, with problems making satisfactory tip jet relights at altitude being solved by that October. Tip jet noise was extremely unpleasant, driving a significantly modified production version with lower pressure tip jets. Despite apparent commercial interest, Fairey was taken over by Westland, causing the program to fizzle out in about 1962.
Same Propulsion System for Hover and Forward Flight (Aircraft # 1 - 26)
Separate Power Plant for Hover (Aircraft # 27 - 29)
Combined Power Plant for Hover (Aircraft # 30 - 37)
Augmented Power Plant for Hover (Aircraft # 38 - 45)
Vision For the Future (and Credits, etc)
V/STOL Aircraft and Propulsion Concepts (The V/STOL "Wheel of Misfortune")
(c) 1997 American Helicopter Society