Hawker P. 1127
| Hawker P. 1127 | |
|---|---|
 Prototype Hawker P.1127 XP831 in 1962 |
|
| Type: | VTOL test vehicle |
| Design country: | |
| Manufacturer: |
Hawker Aviation, Hawker Siddeley |
| First flight: |
November 19, 1960 (free hover) |
| Commissioning: |
October 15, 1964 in the Tripartite Evaluation Squadron |
| Production time: |
1960-1964 |
| Number of pieces: |
P.1127: 6 |
The Hawker P.1127 was a VTOL aircraft that was developed in the early 1960s as a test aircraft and test vehicle for a future Royal Air Force (RAF) operational aircraft. The Kestrel version , which was used for testing under operational conditions, led to the development of the Hawker Siddeley Harrier , the first VTOL fixed-wing aircraft to be mass-produced before the Jakowlew Jak-38 and the current Lockheed Martin F-35 .
history
The Wibault drive concept as a technical requirement
The origins of the concept used in the P.1127 to achieve VTOL capability go back to a development by the French designer Michel Wibault in 1954. In February 1956, Wibault presented his design of a ground attack aircraft ( Gyroptère ) to the French Ministry of Aviation. His drive concept used an adjustable jet outlet instead of a conventional nozzle outlet. The plans provided for the Bristol BE.25 Orion turboprop engine , which drove four radial fans that were arranged in front of the main drive. The fan housings were rotatable so that the thrust could be changed in the direction between vertical and horizontal. The aircraft should be able to take off and land vertically. The Orion engine was chosen because it was the most powerful shaft turbine available .
The aviation ministry was initially inclined to totally reject the concept as it could not be implemented in practice. Eventually, however, he was advised to contact the US-funded Mutual Weapons Development Program (MWDP) and the Advisory Group Aeronautical Research and Development (AGARD) of NATO. A team of experts from the MWDP then carried out an in-depth study of the Wibault concept and consulted Stanley G. Hooker, Technical Director of Bristol Engines . At that time, MWDP was working with the engine manufacturer on the Orpheus engine for the Fiat G.91 . As early as 1953 during his time at Rolls-Royce, Hooker demonstrated the basic feasibility of a jet propulsion-based VTOL concept with the Thrust-Measurung-Rig.
Hooker judged the Wibault drive design to be unsuitable for practical use because of the large amount of space required. Instead, he proposed a further development in which the air could flow out of a central axial compressor via two rotatable pipes on both sides of an aircraft fuselage. The normal nozzle outlet should be at the end of the engine. This would not have allowed VTOL to be used, but it would have given the aircraft STOL properties.
Gordon Lewis from Bristol then suggested connecting a Bristol Orion engine with a large front blower (fan) from which highly compressed air could be directed to the left and right to exhaust nozzles. This construction (Bristol BE.48) was the first of a series of developments that converted Wibault's basic idea into a practically usable drive system. Wibault and Lewis received a patent for this engine concept on January 29, 1957. Further research indicated that the Orion engine was to be replaced by the new Orpheus jet engine, which was lighter and cheaper to manufacture but provided roughly the same thrust. In a further development stage of the now BE.52 engine, the gas generator (compressor, combustion chamber and turbine) of the Orpheus engine was used together with three free-running compressor stages of the low-pressure part of the Olympus . Separate air inlets were necessary for the fan and the Orpheus engine.
Contact Hawker
At the 1957 Paris Air Show , Sydney Camm , Hawker's chief designer, met Major Gerad Morel, who was acting as the French representative for Bristol Engines and Hawker. Morel introduced Camm to the new Bristol engine concepts and the possibilities for future use in VTOL combat aircraft. Camm commissioned his colleague Ralph Hooper to investigate which type of aircraft could best exploit the special capabilities of the BE.52. Hooper quickly realized that the thrust of the engine would not be enough to carry a significant load of weapons and designed a small three-seat STOL liaison aircraft. The first draft for this dates from June 28, 1957 and was already given the project name P.1127. Even with a standing angle of 30 ° between the ground and the fuselage, a V / STOL capability was still beyond the possibilities for weight reasons.
Pegasus evolution
After the failure of the P.1121 project (a Mach 2.5 air superiority fighter), the Hawker design team was able to concentrate fully on the further development of the first P.1127 design. Hooper had the decisive idea to use the two-part, "branched" nozzle outlet of the Rolls-Royce-Nene engine of the Hawker Sea Hawk also on the BE.53. After discussions between Hawker and Bristol, it was decided to make both the low-pressure and high-pressure gas outlets rotatable. To increase the thrust, a two-stage transonic fan was installed upstream in early 1958, which also made it possible to get by with just one air inlet. The fan rotated in the opposite direction as the high-pressure compressor in order to minimize the gyroscopic effect when hovering and at low speeds.
Due to the increased thrust, the construction of a simple tactical V / STOL fighter aircraft that was able to take off from unpaved surfaces could be considered for the first time. The engine that emerged from the joint efforts of Hawker and Bristol was designated BE.53 (from April 1959 BS.53) Bristol Pegasus 1 . The first Pegasus engine then produced 49 kN (11,000 lb) of thrust on the test bench in July 1959. 75% of the engine development costs were funded by the MWDP, while Bristol took over the remaining 25%.
The first prototype
In January 1959, Hawker was informed that the newly formed UK Ministry of Aviation was considering building two prototypes , despite Defense Secretary Sandys' white paper that practically banned the construction of additional manned fighter jets. The RAF planned to procure a further development of the P.1127 as a replacement for the Hawker Hunter in its role of close air support . Hawker was encouraged to begin construction at his own risk prior to the official funding approval. The first preliminary request (GOR.345) of April 1959 a Hunter successors followed in May, the Terms of Reference Specification ER 204D . The two prototypes commissioned were given the RAF serial numbers XP831 and XP836. At the same time, extensive wind tunnel investigations were carried out, which examined the influence of the nozzle jet when hovering on stability, control, cell temperature etc. using models. NASA examined the possibilities of the transition from hovering to level flight (transition) in its large wind tunnel in Langley.
Hawker received the final contract and financing commitment on June 22, 1960 from the Ministry of Aviation. The XP831 was then transported from Kingston on July 15, 1960 by road to the Hawker flight test field in Dunsfold, Surrey. The first Pegasus 2 engine approved for flight operations was delivered to Bristol in September and it was installed on October 13.
Flight testing
From the beginning of the project it was clear that the hovering tests should be started at the earliest possible point in time, as it was foreseeable that previously unknown problems could arise here. The first step was to produce a grid slab that rests on a 1.30 m deep concrete-lined pit and has dimensions of 26.80 m by 12.20 m (88 by 40 ft). The exhaust gases were passed under a cover before being discharged via an upward-facing ramp. The “lip” of the engine intakes was made of metal.
Test pilot Bill Bedford began the development program with four taxi tests on the Dunsfold Aerodrome. Before the first flight, all expendable equipment with a total weight of 320 kg (700 lb) was removed to save weight. Only 17 months after the beginning of the cell construction, Bedford carried out the first tethered hover over the grid on October 21, 1960. The machine was held with a steel cable on the nose landing gear strut and on the ground at both ends of the wing, the freedom of movement of the machine was about 4 ft before a large number of heavy iron disks gradually tensioned the cables. During the second hover on October 24, a cable broke, whereupon the holding cables were generally reinforced.
The first part of the flight test program was completed with two unrestrained hover flights on November 19 and a third on November 24, this time on a concrete surface. These “flights” only lasted about one minute on average. After the satisfactory test results, the Ministry of Aviation ordered four more prototypes of the P.1127 with the RAF serial numbers XP972, XP976, XP980 and XP984 at the end of the year.
After being transported to the Royal Aircraft Establishment (RAE) on March 6, 1961, XP831 made its first conventional flight on March 13. In a total of ten flights it could be proven that the engine works satisfactorily at the speeds of up to Mach 0.8, heights of up to 30,000 ft and accelerations of up to 4.7 g. Hover flights were resumed in May / June 1961. Altitudes of up to around 30 m (100 ft) were reached in a total of 51 hover flights.
The second prototype XP836 also took up the flight program with its maiden flight on July 7, 1961. The first complete transition (transition from hovering to level flight) was achieved with the XP831 for the first time on September 12, 1961. Numerous other flights also confirmed that transitions were possible without any particular difficulties. In a dive, the XP836 succeeded on December 12, 1961 as the first VTOL aircraft to exceed Mach 1. Just two days later, however, the machine crashed when the left front swivel nozzle came loose in flight. The test pilot Bill Bedford was able to save himself from a height of 60 m with the ejection seat. As a result of the accident, the front (“cold”) outlets were made from steel instead of fiberglass.
The third prototype first launched on April 5, 1962, followed by the XP976 as the fourth prototype on July 12. Both the XP831 and XP972 performed together at the 23rd SBAC Show in Farnborough, a highly regarded flight program. These included B. reverse flights with 40 km / h. On October 30, 1962, XP972 crashed as a result of bearing damage and a subsequent engine fire, with the pilot unharmed, but the aircraft had to be written off.
At the beginning of 1963 the general manageability of a VTOL aircraft on an aircraft carrier was examined on the HMS Ark Royal with the XP831. The fifth prototype of the P.1127, which flew for the first time on February 24, 1963, was demonstrated together with the XP831 at the Paris Air Salon in Le Bourget. During a demonstration of the XP831, uncontrollable movements of the exhaust nozzles caused it to crash from the hover, which required several months of repairs. The sixth and last prototype of the P.1127 flew on February 13, 1964 and was the first machine to be built according to the Kestrel standard established at the end of 1962. The fuselage was elongated and the Pegasus 5 engine was installed further forward to increase longitudinal stability in conventional flight. In addition to a new wing ("seventh wing"), this specimen also had a stern parachute for stall and spin tests.
Kestrel
As early as the end of 1962, after 340 flights had been completed as part of the test program, the decision was made in favor of building nine more pre-series machines, which were designated as Hawker Siddeley Kestrel F (GA) Mk 1 and were to be used in the Tripartite Evaluation Squadron (TES). Originally 18 machines were planned for the TES, which was financed by the USA, Great Britain and Germany, but economic reasons led to the order being halved. The serial numbers ran from XS688 to XS696, the Pegasus 5 with a thrust of 69 kN (15,500 lb) was to be used as the engine.
Production of the Kestrel began in mid-1963. Compared to the P.1127, the Kestrel had, among other improvements, a revised cockpit and a suspension for additional tanks or missiles on each wing. However, the latter were not used. In addition, the center fuselage section was lengthened and the engine moved forward by 22 cm (9 in) relative to the tail fuselage. The wingspan was reduced slightly. The first machine (XS688) made its flight on March 7, 1964 and had completed 30 flights by the end of May. The test led, among other things, to the fact that the inflatable rubber lips of the engine inlets on the following machines were replaced by metal lips. After a total of 800 flights of the P.1127 and 340 Kestrel flights, a sufficient standard of the vertical take-off aircraft for use in the TES, which began on October 15, 1964, could be determined.
The use of the TES, which ended on November 30, 1965, showed after nine months with a total of 938 operational flights and over 600 flight hours, the unrestricted use for the intended V / STOL use of makeshift landing sites. One aircraft (XS696) had to be written off, but the pilot was not injured. It was originally planned that after the dissolution of the TES, each country would take over its share of the kestrel stock. However, Germany showed no interest in the two machines assigned to it, so they were shipped to the USA together with the four American copies. The six aircraft were initially given the designation VZ-12 , but this was eventually changed to XV-6A . In the following three years, pilots of the US Air Force, US Army, US Navy and US Marine Corps flew the aircraft as part of the Tri-Service Trials . NASA received two of the aircraft used.
construction
The P.1127 was a design that was essentially constructed around the BS.53 Pegasus engine. The structure of the airframe consisted mainly of light metal alloys with components made of titanium-based alloys and steel. To remove the engine, it could be lifted out of the fuselage after removing the wing. The wing itself was made in one piece, had a clearly negative V-position and had simple flaps and ailerons. The tail unit consisted of a swept fin and rudder and a one-piece swept elevator. The pilot sat on a Martin-Baker Mk. 6 ejector seat .
Flutter valves are used for control at low airspeeds when aerodynamic control is not yet effective . The valves are located in the aircraft nose, in the tail and at the ends of the wing, whereby air at high pressure is fed through pipes from the engine as bleed air to the valves. The valves are connected to the closest aerodynamic controls with the exception of the bow valve, which is operated separately with the joystick. The bleed air was switched on automatically as soon as the engine nozzles were moved out of the horizontal position.
The tandem chassis manufactured by Dowty was chosen for reasons of weight, but also because of the location of the rear nozzle outlets. The rear landing gear with double tires, located near the center of gravity, retracted to the rear just like the outriggers on the wings, while the single-tire nose wheel was retracted forwards. The internal tank capacity was 2650 l (585 gal), an additional tank could be carried at each of the two wing stations instead of a weapon load.
It was controlled conventionally via a joystick and rudder pedals, with which both the aerodynamic control surfaces and the flutter valves were operated. To control the thrust vector, another lever was arranged next to the power lever of the engine. This lever was the only additional control necessary to take advantage of the aircraft's VTOL capability. A backward movement swiveled the nozzles downwards, a fixed stop limited the movement during the vertical start, the limitation for a STOL start was freely adjustable. Since the outlets could be swiveled forward by up to 10 °, a slow reverse flight was also possible.
Further development
After setting up the Tripartite Evaluation Squadron, Hawker began the concrete planning for a supersonic version of the P.1127. The first investigations on this had already taken place in 1960 with the P.1150. A special type of afterburner was planned, in which the combustion should take place behind the front fan (“plenum chamber burning”) in order to generate additional thrust at the front compressor outlets. In August 1961, the draft was that a Bristol-Siddeley BS.100 engine with 147 kN thrust was planned. The construction, now called P.1154, was intended to meet the requirements for a supersonic VTOL fighter aircraft for the RAF and Royal Navy, as set out in OR.356 (Operational Requirement 356). However, the Navy lost interest in 1964 and on February 2, 1965 the new British Labor government stopped development of the P.1154 along with that of the Hawker Siddeley V / STOL transporter HS. 681.
At the same time, the government announced that an upgraded version of the Kestrel would be procured for the RAF. This redesigned model was supposed to be cheaper, if less powerful, than the P.1154, but to a large extent take over its avionics. The hope was that all three countries participating in the TES (Great Britain, USA, Germany) would purchase this aircraft, but this did not happen. Great Britain placed its first order in 1965 for a development batch of six pre-production aircraft with the designation P.1127 (RAF). Germany refrained from placing orders because it favored its own development, the VAK 191B . Despite the very good assessments of the pilots in the US Tri-Service Trials , no further orders were placed, so initially the RAF remained the only operator of the P.1127 (RAF), which was eventually called Harrier .
Harrier
As much as Kestrel and Harrier were outwardly alike, in their “inner workings” they were different constructions. Only 5% of the structural drawings were the same for both samples. The changes that were also visible on the outside concerned the air intakes, the wing layout, the shape of the bow, the tail end, the air brake and the tail fin. The chassis has been completely redesigned, and the Harrier's center of gravity has been shifted forwards to improve longitudinal stability when carrying external loads.
The first "foreign" orders for the Harrier were then placed in December 1969 by the United States Marine Corps .
Whereabouts
| machine | RAF serial no. | First flight | pilot | Whereabouts |
|---|---|---|---|---|
| 1. Prototype | XP831 | October 21, 1960 | Bill Bedford | Badly damaged at the Paris Air Show in June 1963. Has been repaired. Last transfer flight in October 1972. Since May 1992 in the Science Museum London. |
| 2. prototype | XP836 | July 7, 1961 | Bill Bedford | Crashed on December 14, 1961. The pilot Bill Bedford was able to save himself with the ejector seat. |
| 3. Prototype | XP972 | April 5, 1962 | Hugh Merewether | Emergency landing with "economic total loss" in Tangmere after an engine failure on October 30, 1962 on the 49th flight. The pilot Hugh Merewether was unharmed. |
| 4. Prototype | XP976 | July 12, 1962 | Bill Bedford | First 31 flights only conventional. Then used for various V / STOL tests (including control behavior, use on grass fields, head-up display research). Retired and scrapped at the end of 1965. |
| 5. prototype | XP980 | February 24, 1962 | Bill Bedford | Used for various kinds of experiments. Damaged during emergency landing exercises in January 1966. On display in the RNAS Yeovilton Fleet Air Arm Museum with Harrier wing. |
| 6. Prototype | XP984 | February 13, 1963 | Bill Bedford | First example with Kestrel configuration. Had total engine failure when attempting to dive on March 19, 1965 with a successful emergency landing. Equipped with a Harrier wing at the end of 1965 and removed from the P.1127 program. Seriously damaged on landing on October 31, 1975. Exhibited at the Brooklands Museum since 2000 . |
| Kestrel 1 | XS688 | March 7, 1964 | Bill Bedford | Demonstrated in Farnborough in 1964. Handed over to the Tripartite Evaluation Squadron (TES) on May 1, 1964 . Performed 141 flights with registration number "8". Delivered to the USA on November 30, 1965 after completion of the TES mission. Was there the designation "XV-6A" and the USAF serial number 64-18262 and flew until January 1970. Today USAF Museum in Ohio. |
| Kestrel 2 | XS689 | May 28, 1964 | Hugh Merewether | Handed over to TES on April 28, 1965, registration number "9". Gerhard Barkhorn carried out an emergency landing with her. Delivered to the USAF in February 1966 on the s / n 64-18263. From February 1967 used at NASA with the registration number "521". Decommissioned after 210 flights in January 1970. Exhibited at the Smithsonian Institution's National Air and Space Museum since May 1979 . |
| Kestrel 3 | XS690 | 5th August 1964 | Bill Bedford | Delivered to the TES on August 11, 1965 (code "0"). After the last of 64 TES flights (November 26, 1965), she was shipped to the USA in February 1966. Was there XV-6A with the s / n 64-18264. In May 1966 there were also attempts on the USS Independence . Taken over by the USAF to Edwards AFB in August 1966 . In 1968 the US Navy carried out tests on the USS Guam . Currently on display at the Museum of Army Aviation , Fort Rucker, Alabama. |
| Kestrel 4 | XS691 | 5th September 1964 | Duncan Simpson | With the number "1" delivered to the TES immediately after flying in, where it was used for training. Shipped to the USA in April 1966 after the last TES flight on November 26, 1965. Was XV-6A there with the s / n 64-18265 and flew at the Naval Air Test Center (NATC) in Patuxent River. Taken over by the USAF in August 1966 and flew at Edwards AFB until January 1970, then used by NASA to supply spare parts. Destroyed in an accident during road transport to Virginia Air Power Park . |
| Kestrel 5 | XS692 | November 7, 1964 | Bill Bedford | With the registration number “2” delivered to the TES immediately after flying in, where it was used for training in Dunsfold. After the last (234th) TES flight on November 26, 1965, shipped to the USA in February 1966. Was there XV-6A with the s / n 64-18266. Also attempts on the USS Independence . Taken over by the USAF in August 1966 and flew at Edwards AFB, then used by NASA to supply spare parts. When XS694 / 64-18267 (NASA 520) had to be written off, XS692 was made airworthy again as the second NASA 520, decommissioned in January 1970. Now on display at Virginia Air Power Park . |
| Kestrel 6 | XS693 | November 25, 1964 | Duncan Simpson | With the registration number “3” delivered to the TES immediately after flying in, where it was used for training in Dunsfold. Last (214th) TES flight on November 19, 1965. Thereafter it remained in Great Britain and was mainly used for engine tests as part of the Harrier trials. Crash on September 21, 1967, pilot Hugh Rigg was able to save himself with the ejector seat. |
| Kestrel 7 | XS694 | December 10, 1964 | Duncan Simpson | Delivered to the TES immediately after flying in with the registration number “4”. After the last (191st) TES flight on November 26, 1965, shipped to the USA in February 1966. Was there XV-6A with the s / n 64-18267. After attempts at Edwards AFB transferred to NASA and received there the registration number NASA 520 for research flights. Written after a landing accident on August 27, 1967, in which NASA pilot Lee H. Person was uninjured. The aircraft was cannibalized, the wings used for the restoration of the XS688. |
| Kestrel 8 | XS695 | February 19, 1965 | Duncan Simpson | Delivered to the TES immediately after flying in with the number number “5”. After the last (131st) TES flight on November 24, 1965, transferred to RAE Bedford in February 1966 , flew in 1966 with the A & AEE in Boscombe Down and at the aviation shows in Hanover and Farnborough. Written after an accident on March 15, 1967. Reconstructed for training purposes using the XS696 wing, now in the RAF Museum's magazine. |
| Kestrel 9 | XS696 | March 5, 1965 | Bill Bedford | Delivered to the TES immediately after flying in with the registration number “6”. After four flights, on April 1, 1965, take-off accident with US Army pilot Lowell, who was uninjured. The plane was not rebuilt. |
Technical specifications
| Parameter | P.1127 (late) | Kestrel F (GA) Mk.1 |
|---|---|---|
| crew | 1 | 1 |
| Length (without bow probe) | 12.55 m (XP984: 12.80 m) | 12.80 m |
| span | 7.42 m (XP984: 6.96 m) | 6.96 m |
| height | 3.28 m | 3.28 m |
| Wing area | 17.19 m² | 17.28 m² |
| Empty mass | 4627 kg | 4989 kg |
| Takeoff mass | 7031 kg (STOL) | 5897 kg (VTOL) |
| Marching speed | - | 843 km / h |
| Top speed | 1150 km / h | 1207 km / h |
| Service ceiling | 15,200 m | 13,700 m |
| Range | - | 2000 km |
| Engines | 1 × Bristol-Siddeley Pegasus 3 (BS. 53/3) with 49 kN thrust |
1 × Bristol-Siddeley Pegasus 5 with 69 kN thrust |
See also
literature
- Henry Matthews: Hawker P. 1127 & Kestrel . In: Airplane Monthly, November 2002, pp. 57-75.
- Bill Gunston: Hawker P. 1127 & Kestrel . In: Wings Of Fame, Vol. 13, 1998, ISBN 1-86184-025-X .
- The Tripartite Evaluation Squadron . In: FlugRevue, December 1965.
Web links
Individual evidence
- ↑ Principle sketch of the BE.48 on www.asme.org (p. 5) ( Memento of October 21, 2015 in the Internet Archive )