Vertical Take-Off and Landing (VTOL)
The limited speed of the helicopter led to a search for forms of vertical take-off and landing which offered more scope for combat applications. In due course the arguments revolved around two formats: separate engines for lift and forward propulsion and vectored thrust as later used on the Harrier family.
Rolls-Royce Thrust Measuring Rig ('Flying Bedstead')
The TMR was a rig only, made of tubular steel and comprising two opposed Nene 101 engines with most of the thrust directed immediately downwards with 9% of the power being bled off to puffer pipes projecting fore and aft. The first of two rigs, without serial but later XJ314, flew on 9 July 1953 tethered and on 3 August 1954 free and 224 tethered and 16 free flights had been completed by December 1954. It went to the RAE where it eventually crashed on 16 September 1957. The second rig, XK426, flew on 12 November 1956 but it crashed on 27 November 1957 on a tethered flight after hitting the gantry and killing the pilot, Wg Cdr H G F Larson. The TMR had a design thrust to weight ratio of 1.25:1 but the actual figure was slightly less with fuel for about 15 minutes 'flight'.
In 1952 specification ER.143D was issued for a relatively conventional aircraft capable of vertical and horizontal flight and in 1954 Short Bros was awarded a contract for the manufacture of two prototypes XG900 and 905. The shape was to be a delta with a fixed undercarriage, vertical tail surfaces only and a tubby fuselage accommodating five RB.108 engines each of 2,000lbs thrust and a power to weight ratio of 8:1. Four of the engines were clustered vertically, but with some degree of fore and aft movement to provide lift, while a single engine was fitted at the rear for forward power. XG900 was completed and shipped to Boscombe Down for initial trials on 2 April 1957 with only the propulsion engine fitted while XG905 was fully fitted by September when the lift motors were run. The first tethered hovering flight was on 23 May 1958 and the first free flight on 25 October. Both aircraft went to the RAE at Bedford in due course but not before XG905 had crashed, killing the pilot, J R Green, but being rebuilt. Although vectored thrust had overtaken the dual engine approach in Britain the two aircraft remained on trials tasks until retired in 1971, one being preserved in Ulster and the other at Yeovilton.
Hawker P.1127 and Kestrel
In the short history of powered flight there are no more than a dozen or so major milestones. One has to be the P.1127 development aircraft leading via the Kestrel to the vertical take off and landing (VTOL) Harrier. There were two schools of thought in relation to VTOL. Rolls Royce, among others, developed high thrust to weight ratio engines for fixed vertical installation for lift with separate engines for horizontal flight. The format was abandoned in the West but employed on the Yak-36, albeit with a main vectored thrust engine. The P.1127 design began in 1957 of an airframe to be built around the revolutionary BE53 vectored thrust engine. By 1960 the Ministry of Supply issued ER.204D funding two protoypes, the first of which (XP831) flew on 21 October 1960. The installed engine delivered 11,300lb of thrust and weight was reduced to just 10,000lbs for the first tethered 'flight'.
The first conventional take-off was on 13 March 1961 and transition from vertical to horizontal flight in September of the same year. The aircraft went supersonic in a dive on 12 December 1961. By now a second prototype (XP836) had joined the first and in the light of experience numerous design changes were incorporated in subsequent prototypes (XP972, XP976, XP980, XP984). Engines were improved and replaced frequently. In 1959 the BE53 produced only 9,000lbs thrust; as the Pegasus 2 (11,300lbs) it powered the protoype and as the 3 (14,000lbs) it saw the aircraft into transition. The Pegasus 4 (15,500lbs) powered the last prototype. From the outset the P.1127 was intended to act as a prototype for an operational aircraft rather than simply being a research machine. As solutions to problems were identified they were incorporated in airframes. By 1963 there was interest from Germany and the United States in the project and an agreement reached to build nine trials aircraft to examine every aspect of VTOL operations.
Kestrel F(GA) Mark 1
The Kestrel was the response to the agreement and in effect the prototype was the last P.1127 development aircraft. It was produced to requirement GOR.345. Compared to the earlier P.1127s it had the Pegasus 5 of 15,500lbs thrust, inflatable intake lips, a swept wing, longer fuselage and a tailplane of increased span. Nine Kestrels were constructed (starting XS688) and the Tripartite Evaluation Squadron was formed at West Raynham in March 1965 within the Central Fighter Establishment. The unit flew the Kestrel intensively for nine months during which 930 sorties covering 600 hours were flown. The type was never more than an interim vehicle and from January 1965, at which time the intended supersonic P.1154 was cancelled, the subsonic fully operational P.1127/Kestrel derivative was ordered. Those trials aircraft transferred to the US were given the designation XV-6A.
A number of types in this section has been used to examine specific problems but usually in a wider context or as by-products or after the original need had been addressed. The types described in the section are a miscellany built for a wide range of research.
An innovative high-lift wing designed by R T Youngman was wedded to a re-designed Proctor Mk IV fuselage to evaluate fullspan slotted flaps. As VT789 the type was designated P.46 and flew on 5 February 1948 conferring excellent low speed lift. It was evaluated By RAE and later sold to the designer as G-AMBL.
Reid & Sigrist RS.4 Bobsleigh
The RS.3 Desford was a twin-engined monoplane with fixed undercarriage built as a trainer, although only one was made, G-AGOS. It was bought by the Ministry of Supply for prone pilot research in 1948, it being believed that fast jets would require a very low frontal profile. The nose was lengthened and glazed and provision made for a pilot lying prone while retaining the original cockpit; the name as changed to Bobsleigh to reflect the driving position. The first flight, as VZ728, was made on 13 June 1951 and tests were conducted over several years until the aircraft reverted to the civil register in 1956. Research continued later on a specially adapted Meteor 8, WK935, which flew on 10 February 1954 with the Institute of Aviation Medicine. It was retired after a year and is preserved at Cosford.
An Auster T Mk 7, VF665, was modified by Marshalls to specification ER.184D to enable Cambridge University to explore boundary-layer control by suction. For this purpose a revised wing, stronger undercarriage and enlarged fin and rudder were fitted together with a small turbine to provide the suction through wing perforations. Lift was greatly improved and the M.A.4 flew from early 1959 until it was lost in a crash on 8 March 1966.
Handley Page HP.84 Hermes II
The Hermes was a four-engined airliner which was essentially a lengthened Hastings constructed to specification C.35/46. The first Mark II aircraft, G-AGUB was also first allocated PW943 and later VX234 when it was used by the MoS for trials work.
Avro 688, 689 Tudor
The Tudor was a four-engined pressurised airliner designed to carry just twelve passengers across the Atlantic. Tudor I prototype, G-AGPF, also carried the serial TT176 and it later became VX192 with the MoS. Twelve were built and TS866-875 and VD273-278 were allocated. G-AGST/TT181 became a Tudor IV. G-AGRK/TS874 and G-AGRL/TS875 went to the MoS. The larger Mark II included allocations TJ161 and TJ164 (both cancelled), TS884-892, TS893-902 (G-AJJS- G-AJKB), TS909-912 (G-AKTH-G-AKTK) and VD281-316, VD340-352 which latter comprised a cancelled BOAC order. The second completed aircraft, G-AGRY undertook tropical trials as VX202 but only five of this variant were completed. G-AGRZ/VZ366 and G-AGSA/VZ720 were also allocated for use with Flight Refuelling and Rolls-Royce respectively. The Tudor III was a smaller aircraft based on the Mark I and for use by Cabinet Ministers. They were G-AIYA/VP301 and G-AJKC/VP312. Thirteen Tudor IV were built with Merlin 622/623 engines and an extended fuselage. At least two had serials intended for the unbuilt Mark Is, TS868 and 869. The Mark V was designed as a 44 seater but was, in fact, used as a tanker through the Berlin airlift. Serials TS903 - 908 covered G-AKBY-G-AKCD. The Tudor VII had Hercules engines and one was built; it started life as nominal TS883 but flew as G-AGRX/VX199 with the Ministry of Supply and Aircaft Production. Finally Tudor 1 TT181 became VX195 as the sole Mark 8 with four Nene jet engines for trials.
Avro Type 706 Ashton
Experience with the Tudor Mk 8 highlighted the problems of a tailwheel configuration for jet-engined aircraft. The Type 706 Ashton was in essence a Tudor development with nosewheel undercarriage. Six were ordered by the MoS in four configurations solely as research vehicles. The Mark 1, WB490, was based on Tudor 2 TS896/G-AJJV and featured a nose probe; it flew on 1 September 1950 and served with the A&AEE until 1957. Mark 2 WB491 flew on 2 August 1951. Based on Tudor TS897/G-AJJW it was operated by the RAE until 1960 as an engine test-bed with a variety of engines fitted in a ventral pod under the centre fuselage section. Three Mark 3 aircraft were built, all with shorter pressurised fuselage sections and based on Tudor 2 airframes. They were WB492 ex TS898/G-AJJX (first flight 6 July 1951), WB493 ex TS899/G-AJJY (first flight 18 December 1951) and WE670 ex TS901/G-AJKA (first flight 9 April 1952. WB492 was fitted with underwing nacelles to contain bombs and served with the RRE from 1952 to 1955 where it was fitted with a radar scanner under the centre fuselage. WB493 was used by the Bristol Aeroplane Company from 1952 to 1962 for engine test-bed work. At one time fitted with two Olympus engines outboard of the Nenes and as such was the only British six-jet aircraft to fly; in 1956 it secured the world altitude record of 63,668ft. WE670 was used by the A&AEE for bomb ballistics trials from 1952 and then went to Rolls-Royce as a test-bed until 1962 The sole Mark 4 was WB494 ex TS900/G-AJJZ which flew on 18 November 1952. It had a pressurised ventral pannier for the bomb-aimer and went to the RAE for visual bombing research then on to de Havilland for engine development until 1962.
Armstrong Whitworth A.W.55 Apollo
The Armstrong Whitworth Apollo was built to specification C.16/46 as a DC-3 replacement. It was a sleek design with four low-profile Mamba turboprop engines and first flew as VX220 on 10 April 1949. It was later registered G-AIYN while the second prototype was VX224/G-AMCH which was used by the A&AEE and ETPS. The type was not a success.
Specification ER.134T called for a research aircraft capable of flying at sustained speeds in excess of Mach 2 in order to examine the effects of kinetic heating on airframes. The Bristol design, powered by two de Havilland Gyron engines of up to 20,000lbs thrust, was selected and two aircraft, XF923 and XF926, were ordered. (Three further aircraft, XK429, 434 and 436, were cancelled.) The aircraft was built of stainless steel with a long, thin, fuselage, high set tailplane and with the engines mounted midway along extremely thin wings. First flight of XF923 was on 14 April 1962 and the second machine flew a year later. The programme was a failure, with speed limited to Mach 1.88 and very poor flight duration, and it ceased in 1964 with XF926 preserved at Cosford.
This pure research aircraft was built to specification ER.189D to provide a tool for exploring the use of the jet exhaust channelled through the wing trailing edge to produce a jet flap. Two airframes were ordered, XN714 and 719, but the latter was cancelled, the former flying on 26 March 1963 from RAE Bedford. The H.126 was an ungainly aircraft with a single Orpheus 805 engine, fixed undercarriage and high-set tailplane. It was flown at RAE for several years and was eventually transferred to Cosford where it is preserved.