Once again John Farley stepped
into the breach. This time it was because David Scrimgeour was not well
enough to come to Kingston, on 14 March, and talk about the Kestrel
Squadron. However, Members were not too disappointed because John gave
his talk on the history of V/STOL aircraft development using Mike
Hirschberg's V/STOL wheel.
This classifies the various
basic ways of achieving V/STOL (excluding helicopters), sub-divides
each into engineering solutions and finally gives examples of types
falling into the various categories. The wheel shows, John explained,
45 aircraft starting with the tilt-rotor Transcendental Model 1-G of
1954 and finishing with the contemporary F-35 Lightning II Joint Strike
The V/Stol Wheel Of Misfortune
Turning to the individual types John described their
configurations and outlined their histories and achievements. First of
the shaft driven tilt-rotor types was the twin-rotor Transcendental 1-G
which completed its first transition in December 1954. It was lost due
to rotor control failure. The later Model 2 was unable to compete with
the twin rotor Bell XV-3 of 1955, built for US Army but also flown for
15 years by NASA and the USAF on research.
propellers were employed by Curtiss-Wright on their twin-propeller
X-100 flown with some success in 1960 and on its successor, the
four-propeller (at the tips of a pair of tandem wings) X-200 or X-19.
Hovered and flown conventionally in 1963, it never completed transition
and crashed in 1965. Tilting duct types were the 'successful' (ie
VTO-double transition-VL) twin-duct Doak 16 and the four-duct Bell
X-22A (1966), and the twin-duct Nord 500 which achieved tethered hover
Moving on to tilt-wings John covered the
'successful' twin-prop Vertol 76/VZ-2 (1957), the twin-prop Hiller X-18
(1959) which never hovered and was scrapped, and the four-prop
LTV-Hiller-Ryan XC-142 (1964). Five were built and evaluated by the US
services but handling and mechanical problems caused a number of
accidents. The four twin-prop Canadair CL-84s (1965) were also
subjected to lengthy service evaluation but came to nought.
The Bell XV-15 (1977) was a tilt-rotor type with twin tilting
engines at the tips of a fixed wing. Two examples were flown very
successfully and led to the Bell Boeing Vertol V-22 Osprey (1989)
which, after a long and troubled development programme, and a number of
accidents, is about to enter service with the USMC.
tilt-jets were represented by the Bell Model 65 ATV (Air Test Vehicle)
of 1954 which carried two tilting J-44s on the sides of a Schweizer
sailplane fuselage beneath a Cessna 170 wing. It did well everything a
VTOL should do apart from a full transition, precluded by lack of power.
Deflected slipstream was tested by the Robertson Aircraft
Corporation in a VTOL, four-seat, twin Lycoming, high wing
machine with a sliding flap system. It flew tethered in 1957 but was
not pursued. The twin propeller Ryan VZ-3 was underpowered and could
hover only in a light wind. Ryan's VZ-5 Fledgling with four propellers
flew tethered only, in 1959.
In 1957 the Bell X-14
successfully pioneered vectored thrust. Built for the USAF it flew on
for many years with NASA on research programmes. Hugh Merewether flew
the X-14 in preparation for the P.1127 test programme. We all know the
P.1127 story which started in 1960 and led to the Harrier series of
in-service fighters with one engine, the Bristol Pegasus, and four
In 1963 the twin engined, two nozzle Soviet
Yak-36 flew, demonstrated complete transitions and high speed flight
and led to the Yak-36M/Yak-38. The latest manifestation of vectored
thrust was the Boeing X-32B JSF contender. This two nozzle design with
straight through flow for conventional flight was defeated in a
'fly-off' by Lockheed-Martin's X-35B, its main problem being hot gas
reingestion in spite of an intake jet screen provided by fan bleed air.
Tail-sitting VTOL proved to be a fascinating dead-end. The
USN-funded turboprop Lockheed XFV-1 and the Convair XFY-1 flew in 1954
but only the latter completed the transition sequence. The Avon powered
Ryan X-13 for the USAF was launched from and retrieved by a cable
stretched between two arms on the flat bed of a tipping truck, by means
of a hook under the nose. Flown in 1951 complete transitions and high
speed flight were demonstrated. In France the annular wing, Atar
powered SNECMA C-450 Coleoptere of 1959 hovered but crashed on
its ninth flight.
To some extent
utilising data from the Rolls-Royce 'Flying Bedstead' of 1953, the
RAE's Short SC-1 aircraft had four R-R RB-108 lift engines plus one for
cruise. Fully autostabilised, the two built carried out much valuable
research flying from 1957.
This multi-engined concept
promoted by Rolls-Royce led to the experimental Dassault Balzac, a
converted Mirage III prototype, with eight RB-108 lift engines and a
Bristol Orpheus for cruise. Flown in 1962 it accomplished transitions
and high speed flight, but achieved the distinction of fatally crashing
twice. Its successor, the bigger and heavier Mirage IIIV, with eight
RB-163 lift engines and a SNECMA TF-104/106 or P&W TF-30 for
cruise. Although the IIIV fully demonstrated VTOL and Mach 2
capabilities, the concept's complexity and weight led to another
Lift plus lift/cruise engined hybrids
included the German VJ-101 of 1963 with six R-R RB.145 engines, two in
a swivelling pod at each wing tip for lift and cruise, and two in the
forward fuselage for lift only. The second aircraft had reheated wing
tip engines. VTOL and Mach 1+ were demonstrated but the project
Dornier's Do-31 was a V/STOL
transport with two underwing Pegasus for lift and cruise and wing-tip
pods each containing four R-R RB.162 lift engines. Two hovering rigs
preceded the Do.31 which flew in 1967. Although V/STOL and conventional
flight were fully demonstrated and a research programme was flown by
NASA this project also faded away.
In the USA Ryan
converted their XV-4A to take four J-85s in the fuselage for lift and
two beside the fuselage for cruise to become the XV-4B Hummingbird II.
Flown in 1969 it crashed in less than a year.
Germany's last attempt was the VFW-Fokker VAK-191B. This had a
centrally mounted, four nozzle, R-R RB.193 vectored thrust lift/cruise
engine with a R-R RB.162 lift engine in the front and rear fuselages.
It was one of the most complex V/STOL aircraft ever built. Flown from
1971, three prototypes were built but the German Government abandoned
their VTOL fighter requirement.
In the Soviet Union
the Yak-38 Forger naval fighter of 1971 had a two nozzle vectored
thrust Tumansky R-27V-300 in the centre fuselage and two Rybinski
RD36-35 lift engines in the forward
fuselage. As an engine
failure would cause catastrophic pitching an automatic ejection system
fired the pilot's seat if pitch attitude changed by more than 10
degrees. John showed an impressive film of such an ejection off the bow
of an aircraft carrier. 231 aircraft were built and served for 15 years
paving the way for what was to be its supersonic successor, the Yak
This aircraft had a similar layout to the -38
except that the reheated Soyuz/Kobchenko R-79V-300 lift/cruise
engine exhausted through a single vectoring nozzle between two tail
booms. The lift engines were Rybinski/Novikov RD-41s. Sadly the project
fell victim to drastic cuts in the Russian defence budget. This
successful Mach 1.8 ASTOVL fighter appeared at Farnborough and was the
subject of a teaming agreement with Lockheed-Martin for the JAST/JSF
Another form of hybrid had tip jet driven
rotors which were unloaded and autorotated at cruising speeds, with
propeller propulsion. The USAF's McDonnell XV-1 of 1955 had a rotor
driven by tip mounted pressure jets and a pusher propeller. A
Continental piston engine drove a compressor for VTOL and the propeller
for cruise. VTOL and conversion to horizontal flight were successfully
demonstrated but the principle was not pursued.
However, in England Fairey's Rotodyne VTOL airliner was
intended to carry 48 passengers from and to city centres. It had a 90
ft diameter rotor and low aspect ratio wings mounting two Napier Eland
turboprops. These drove tractor propellers and compressors delivering
compressed air to the rotor tip jet units. Its performance was entirely
satisfactory but its tremendous noise during take-off made it quite
unsuitable for its intended use. During question time the Fairey
Gyrodyne and Jet Gyrodyne, Rotodyne predecessors, were discussed.
Several attempts were made to augment VTO/hover thrust by means of
ejector nozzles or fans. The US Army's Ryan XV- 4A Hummingbird had a
P&W JT12A turbojet each side of the fuselage exhausting rearwards
for cruise. For VTOL/hover the exhausts were diverted downwards via
complex cross-connected ducting to ejector nozzles in the fuselage. It
flew in 1962, with transitions in 1963 and a fatal crash in 1964. The
expected augmentation ratio was not achieved and the lift system took
up a large percentage of the fuselage volume.
Rockwell XFV-12A canard fighter with ejector slots in the foreplane and
wings was a complete failure, this supersonic design never achieving
its planned augmentation ratio or even a VTO.
fan-in-wing configuration was pioneered by the Vanguard 2C Omniplane
which had a fan in each wing and a tail mounted propulsive ducted fan.
The Ryan XV-5A's twin J-85 exhausts could be diverted to two large wing
mounted tip turbine driven fans and a smaller similar unit in the nose
for vertical thrust, or could exit through normal tailpipes for
wingborne flight when shutters covered the fans. First flown in 1964
the complete transition sequence was demonstrated satisfactorily before
the first aircraft was lost. A second flew on until 1966 when it too
crashed but was rebuilt as a research aircraft for NASA, the XV-5B
The contemporary manifestation of the fan concept is the
Lockheed-Martin X-35B Joint Strike Fighter prototype. Here a nose
mounted, shaft driven fan is clutched-in for vertical flight and the
single vectoring engine nozzle, using Yak-141 technology, is
articulated downwards. In this configuration the hot engine exhaust is
far removed from the intakes minimising hot gas reingestion, and the
Rolls-Royce fan is very efficient; for a weight penalty of 6,000 lb,
16,000 lb of vertical thrust is gained. Modern fly-by-wire and
autostabilisation techniques make flying the aircraft straightforward
and although the design is complicated compared with the Harrier modern
technology renders it practical.
touched on some rotor types. The 1960 Kamov Ka-22 was a large transport
compound or winged helicopter in which wing tip mounted turboshaft
engines drove propellers for propulsion and rotors which were powered
for take-off but autorotated in the cruise. It achieved 221 mph
and lifted 36,000 lb to 8,500 ft. Piasecki's 16-H1 of 1962 was an early
research compound helicopter but the Lockheed AH-56 Cheyenne was
a successful winged tandem two-seat attack compound helicopter for the
US Army. Flown in 1967 budget cuts led to its demise after ten had been
In conclusion John remarked that out of
all this effort had emerged just two in-service types: the Harrier
series and the Yak-38, intended to be the precursor of the supersonic
Yak-141. However, the V-22 Osprey will enter service shortly and the
F-35B Lightning II, developed from the X-35B, is expected to enter
service with the USMC and Royal Navy in 2015.