Hawker P.1127
Encyclopedia

The Hawker P.1127 and the Hawker Siddeley Kestrel FGA.1 were the experimental and development aircraft that led to the Hawker Siddeley Harrier, the first vertical and/or short take-off and landing (V/STOL
V/STOL
Vertical and/or short take-off and landing is a term used to describe aircraft that are able to take-off or land vertically or on short runways. Vertical takeoff and landing describes craft which do not require runways at all...

) jet fighter-bomber. Kestrel development began in 1957, taking advantage of the Bristol Engine Company's choice to invest in the creation of the Pegasus
Rolls-Royce Pegasus
The Rolls-Royce Pegasus is a turbofan engine originally designed by Bristol Siddeley, and now manufactured by Rolls-Royce plc. This engine is able to direct thrust downwards which can then be swivelled to power a jet aircraft forward. Lightly loaded, it can also manoeuvre like a helicopter,...

 vectored-thrust
Thrust vectoring
Thrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....

 engine. Testing began in July 1960 and by the end of the year the aircraft had achieved both vertical take-off and vertical flight. The test program also explored the possibility of use upon aircraft carriers, landing on in 1963. The first three aircraft crashed during testing, one at the 1963 Paris Air Show
Paris Air Show
The Paris Air Show is the world's oldest and largest air show. Established in 1909, it is currently held every odd year at Le Bourget Airport in north Paris, France...

.

Improvements to future development aircraft, such as swept wings and more powerful Pegasus engines, led to the development of the Kestrel. The Kestrel was evaluated by the Tri-partite Evaluation Squadron, made up of military pilots from Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and West Germany
West Germany
West Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....

. Later flights were conducted by the U.S. military and NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

.

Related work on a supersonic aircraft, the Hawker Siddeley P.1154
Hawker Siddeley P.1154
The Hawker Siddeley P.1154 was a planned supersonic vertical/short take-off and landing fighter aircraft designed by Hawker Siddeley Aviation . Developed alongside the subsonic and smaller Hawker Siddeley P.1127/Kestrel, the P.1154 was derived from the P.1150. The P.1150 proposal did not meet NATO...

, was cancelled in 1965. As a result, the P.1127 (RAF), a variant more closely based on the Kestrel, was ordered into production that year, and named Harrier in 1967. The Harrier would go on to service with the UK and several nations, often as a carrier-based aircraft.

Background

In 1957, the Bristol Engine Company informed Sydney Camm of Hawker that they had a project to combine their Olympus
Rolls-Royce Olympus
The Rolls-Royce Olympus was one of the world's first two-spool axial-flow turbojet aircraft engines, originally developed and produced by Bristol Aero Engines. First running in 1950, its initial use was as the powerplant of the Avro Vulcan V Bomber...

 and Orpheus jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...

s to produce a directable fan jet. The original idea on which the engine, named Pegasus,The name "Pegasus
Pegasus
Pegasus is one of the best known fantastical as well as mythological creatures in Greek mythology. He is a winged divine horse, usually white in color. He was sired by Poseidon, in his role as horse-god, and foaled by the Gorgon Medusa. He was the brother of Chrysaor, born at a single birthing...

" for the engine was in keeping with Bristol's tradition of naming engines after figures from classical mythology
Classical mythology
Classical mythology or Greco-Roman mythology is the cultural reception of myths from the ancient Greeks and Romans. Along with philosophy and political thought, mythology represents one of the major survivals of classical antiquity throughout later Western culture.Classical mythology has provided...

was based came from Michel Wibault, a French aviation consultant. Several adaptions and enhancements were made by Bristol to reduce size and weight over Wibault's original concept. Hawker took the planned Pegasus engine as a basis for a plane that could meet the current NATO specification for a Light Tactical Support Fighter. Prior to the P.1127 project, Hawker Aviation had been working on a replacement for the Hawker Hunter
Hawker Hunter
The Hawker Hunter is a subsonic British jet aircraft developed in the 1950s. The single-seat Hunter entered service as a manoeuvrable fighter aircraft, and later operated in fighter-bomber and reconnaissance roles in numerous conflicts. Two-seat variants remained in use for training and secondary...

—the Hawker P.1121
Hawker P.1121
-Bibliography:*Mason, Francis K. Hawker Aircraft Since 1920. London. Conway Maritime Press Ltd, 1991. ISBN 0 85177 839 9...

. However, the P.1121 was cancelled shortly after the 1957 Defence White Paper
1957 Defence White Paper
The 1957 White Paper on Defence was a British white paper setting forth the perceived future of the British military. It had profound effects on all aspects of the defence industry but probably the most affected was the British aircraft industry...

, which advocated a policy shift away from manned aircraft and towards missiles.

By the end of 1958, barely eighteen months after the start of the project, all the main features of the P.1127 were developed with one exception, the reaction control system - this was resolved by April 1959. As the P.1127 had been developed at a time of deep UK defense cuts; Hawker had to seek commercial funding, significant engine development funding came from the U.S. Wind tunnel tests conducted by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 Langley Research Center
Langley Research Center
Langley Research Center is the oldest of NASA's field centers, located in Hampton, Virginia, United States. It directly borders Poquoson, Virginia and Langley Air Force Base...

 using a sub-scale model showed acceptable flight characteristics. Hawker test pilot Hugh Merewether
Hugh Merewether
Hugh Merewether was a British test pilot who pioneered the vertical and short take-off and landing techniques that led to the development of the Hawker Siddeley Harrier....

 went to the U.S. at NASA's request to fly the Bell X-14. In March 1959, the company's board of directors (Hawker Siddeley then) decided to privately fund two P.1127 prototypes. In late 1959 the British Ministry of Supply
Ministry of Supply
The Ministry of Supply was a department of the UK Government formed in 1939 to co-ordinate the supply of equipment to all three British armed forces, headed by the Minister of Supply. There was, however, a separate ministry responsible for aircraft production and the Admiralty retained...

 contracted for two P.1127 prototypes.

P.1127

The first prototype P.1127, serial XP831, was delivered in July 1960 for static engine testing, and in October the Pegasus flight engine was made available. The first tethered flight took place at Dunsfold Aerodrome
Dunsfold Aerodrome
Dunsfold Aerodrome in Surrey, England, near the village of Cranleigh, was built by the Canadian Army and civilian contractors as a Class A Bomber Airfield for Army Co-operation Command...

 on the 21 October and free flight hover was achieved on 19 November, after which the first publicity photos were released. The second prototype made its first take off conventionally on 7 July 1961. The two aircraft proceeded to close the gap between vertical take off and flight, which was achieved by 8 September 1961.

Four more prototypes were ordered. Throughout this period improved Pegasus engines were being developed, with the Pegasus 3 being capable of 15,000 lbf (67 kN) of thrust. Apart from this, the first four aircraft were quite similar, but the fifth, XP980, introduced the taller fin and tailplane anhedral later seen on the Harrier. The fourth machine was used, in part to give the Hawker production test pilots P.1127 familiarisation. The first carrier vertical landing was performed by the first prototype on in 1963. The last P.1127, XP984, introduced the swept wing. It was eventually fitted with the 15,000 lbf (66.7 kN) Pegasus 5 and functioned as the prototype Kestrel.

The first three P.1127s crashed, the second and third during development. The first prototype (XP831) crashed at the Paris Air Show
Paris Air Show
The Paris Air Show is the world's oldest and largest air show. Established in 1909, it is currently held every odd year at Le Bourget Airport in north Paris, France...

 in 1963 but was fully repaired and resumed development flying. All the pilots involved survived.

Kestrel FGA.1

Nine evaluation aircraft were ordered as the Kestrel FGA.1, an improved version of the P.1127, the first flying on 7 March 1964. The Kestrel had fully swept wings and a larger tail than the early P.1127s, and the fuselage was modified to take the larger 15,000 lbf (85 kN) Pegasus 5 engine as in the P.1127/Kestrel prototype XP984. Due to interest from the U.S. and Germany, the Tri-partite Evaluation Squadron (TES) was formed on 15 October 1964 at RAF West Raynham
RAF West Raynham
RAF West Raynham was a Royal Air Force station located west of the village of West Raynham in Norfolk, England. It opened in the 1930s and closed in 1994. During the Second World War, RAF Bomber Command operations from RAF West Raynham claimed 86 aircraft. The site was sold by the Ministry of...

, staffed by military test pilots from Britain, the United States and West Germany.

The Kestrel's first flight was on 7 March 1964. These equipped the Tripartite Evaluation Squadron formed at RAF West Raynham
RAF West Raynham
RAF West Raynham was a Royal Air Force station located west of the village of West Raynham in Norfolk, England. It opened in the 1930s and closed in 1994. During the Second World War, RAF Bomber Command operations from RAF West Raynham claimed 86 aircraft. The site was sold by the Ministry of...

 in Norfolk
Norfolk
Norfolk is a low-lying county in the East of England. It has borders with Lincolnshire to the west, Cambridgeshire to the west and southwest and Suffolk to the south. Its northern and eastern boundaries are the North Sea coast and to the north-west the county is bordered by The Wash. The county...

 in March 1965. The Evaluation pilots developed a typical sortie routine for the Kestrel of conducting short take-offs (STO) and returning to base on vertical landings. This manner of operation (STOVL
STOVL
STOVL is an acronym for short take off and vertical landing.This is the ability of some aircraft to take off from a short runway or take off vertically if it does not have a very heavy payload and land vertically...

) was judged to be the optimal practice. Operating from rough airstrips was also trialled at nearby RAF Bircham Newton
RAF Bircham Newton
RAF Bircham Newton was a Royal Air Force airfield in the west of the county of Norfolk in the United Kingdom, eight miles west of Fakenham.-History:...

, where the aircraft proved adept at traversing boggy ground and taking off from a variety of temporary ground coverings. During testing one aircraft was lost; the evaluations were finalised in November 1965.

Six of the eight surviving evaluation aircraft (the three allocated to the U.S. plus those allocated to Germany) were transferred to the U.S. for evaluation by the Army, Air Force, and Navy as the XV-6A Kestrel. After Tri-Service evaluation they were passed to the USAF for further evaluation at Edwards Air Force Base
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...

, except for two that were assigned to NASA. One of the two remaining British-based Kestrels was attached to the Blind Landing Experimental Unit (BLEU) at RAE Bedford
RAE Bedford
RAE Bedford based near the village of Thurleigh, north of the town of Bedford in England, has been the site of major aircraft experimental development work....

 and the other, XS693, went to Blackburn for modification to take the uprated Pegasus 6 engine.

In addition to some strengthening, there were alterations to the air intake, which had throughout the P.1127 and Kestrel series featured an inflatable lip to smooth the intake airflow when the aircraft was almost stationary. There were concerns about the service life of these devices, so they were replaced with conventional suction relief doors. Experience gained during naval testing onboard the commando carrier HMS Bulwark
HMS Bulwark (R08)
The sixth HMS Bulwark of the Royal Navy was a 22,000 tonne Centaur-class light fleet aircraft carrier.-Construction:Bulwark was laid down by the Harland & Wolff shipyard in Belfast on 10 May 1945...

 in 1966 convinced project officers that less reactive materials would be substituted for all uses of magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 in the Kestrel's airframe, in any further prototypes and production aircraft. The Kestrel became the prototype for pre-production Harriers.

P.1127 (RAF)

NATO requirement NBMR-3 specified a VTOL aircraft, but one with the performance of an aircraft such as the F-4 Phantom II along with VTOL capability. Hawker drafted the P.1150, a supersonic P.1127, and the P.1154
Hawker Siddeley P.1154
The Hawker Siddeley P.1154 was a planned supersonic vertical/short take-off and landing fighter aircraft designed by Hawker Siddeley Aviation . Developed alongside the subsonic and smaller Hawker Siddeley P.1127/Kestrel, the P.1154 was derived from the P.1150. The P.1150 proposal did not meet NATO...

, which would meet NBMR-3. The P.1154 was a winner of the NATO competition and prototype construction was already underway at the point of cancellation in 1965. The French government withdrew shortly after its selection over the Dassault Mirage IIIV
Dassault Mirage IIIV
|-See also:-Bibliography:* Breffort, Dominique and Andre Jouineau. "The Mirage III, 5, 50 and derivatives from 1955 to 2000." Planes and Pilots 6. Paris: Histoire et Collections, 2004. ISBN 2-913903-92-4....

. The RAF then began looking at a simple upgrade of the Kestrel, and issued Requirement ASR 384 for a V/STOL ground attack jet, known as the P.1127 (RAF).

In late 1965, the RAF ordered six pre-production P.1127 (RAF) aircraft. The first P.1127 (RAF) flew on 31 August 1966. An order for 60 production aircraft was formally received by Hawker Aviation in early 1967; at this time the aircraft received the Harrier GR.1 designation. The Harrier would go on to be a successful aircraft in British service, and was exported to several nations, often seeing usage as a carrier-based aircraft.

Variants

P.1127
Experimental V/STOL fighter, two prototypes and four development aircraft.

Kestrel FGA.1
Aircraft for the tripartite evaluation squadron, nine built, six later transferred to the United States where they were designated XV-6A.

P.1127 (RAF)
Development V/STOL ground attack and reconnaissance fighter, six built as pre-production evaluation aircraft before the type was ordered into production as the Harrier GR.1. First aircraft flew from Dunsfold on 31 August 1966.

XV-6A
United States military designation for the six Kestrel FGA.1 transferred to the U.S.

VZ-12
U.S. Army designation for two P.1127 development aircraft, not delivered.

Operators

  • Aeroplane and Armament Experimental Establishment
    Aeroplane and Armament Experimental Establishment
    The Aeroplane and Armament Experimental Establishment was a research facility for British military aviation from 1918 to 1992.-History:...

     P.1127 and Kestrel trials and evaluation
  • Royal Air Force
    Royal Air Force
    The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

    • Central Fighter Establishment - Kestrel (P.1127) Evaluation Squadron (also known as the Tripartite Evaluation Squadron), nine Kestrel aircraft allocated for evaluation in 1965. One aircraft was lost in an accident, six aircraft later passed to the United States Army, one to the Royal Aircraft Establishment
      Royal Aircraft Establishment
      The Royal Aircraft Establishment , was a British research establishment, known by several different names during its history, that eventually came under the aegis of the UK Ministry of Defence , before finally losing its identity in mergers with other institutions.The first site was at Farnborough...

       and one to Hawker Siddeley for further trials.
  • Royal Aircraft Establishment
    Royal Aircraft Establishment
    The Royal Aircraft Establishment , was a British research establishment, known by several different names during its history, that eventually came under the aegis of the UK Ministry of Defence , before finally losing its identity in mergers with other institutions.The first site was at Farnborough...

     P.1127 and Kestrel trials and evaluation.


  • United States Army
    United States Army
    The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

     (aircrew participated in both the Tri-partite Evaluation Squadron and as part of the American XV-6A Tri-service evaluation team. Had three Kestrel aircraft allocated after the evaluation at West Raynham and also acquired the three allocated to Germany. Four later transferred to the United States Air Force and two to the National Aeronautics and Space Administration).
  • United States Air Force
    United States Air Force
    The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

     (aircrew participated in both the Tri-partite Evaluation Squadron and as part of the American XV-6A Tri-service evaluation team but had no aircraft allocated after the evaluation at West Raynham, four former United States Army aircraft operated for trials).
  • United States Navy
    United States Navy
    The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

     (aircrew participated in both the Tri-partite Evaluation Squadron and as part of the American XV-6A Tri-service evaluation team but had no aircraft allocated after the evaluation).
  • NASA
    NASA
    The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

     operated two former United States Army Kestrels.


  • Luftwaffe
    Luftwaffe
    Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....

     (aircrew participated in the Tri-partite Evaluation Squadron, three allocated Kestrel aircraft not delivered and passed to United States Army)

Aircraft on display

  • P.1127 XP831
    United Kingdom military aircraft serials
    In the United Kingdom to identify individual aircraft, all military aircraft are allocated and display a unique serial number. A unified serial number system, maintained by the Air Ministry , and its successor the Ministry of Defence , is used for aircraft operated by the Royal Air Force , Fleet...

     on display at The Science Museum
    Science Museum (London)
    The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....

    , London, England.
  • P.1127 XP980 (fitted with a Harrier GR.1 wing) is on display at the Fleet Air Arm Museum
    Fleet Air Arm Museum
    The Fleet Air Arm Museum is located north of Yeovil, and south of Bristol. It has an extensive collection of military and civilian aircraft, as well as models of Royal Navy ships, especially aircraft carriers. Some of the museum has interactive displays...

    , Yeovilton, England.
  • P.1127 XP984 (temporarily fitted with an earlier P.1127 wing) is on display at the Brooklands Museum
    Brooklands Museum
    Brooklands Museum is an independent charitable trust, established in 1987, whose aim is to conserve, protect and interpret the unique heritage of the Brooklands site. It is located south of Weybridge, Surrey and was first opened regularly in 1991 on of the original 1907 motor-racing circuit...

    , Surrey, England.
  • Kestrel FGA.1 XS695 is currently under restoration by the Royal Air Force Museum Cosford
    Royal Air Force Museum Cosford
    The Royal Air Force Museum Cosford is a museum dedicated to the history of aviation, and the Royal Air Force in particular. The museum is a non-departmental public body sponsored by the Department for Culture, Media and Sport and a registered charity...

     England.
  • P.1127(RAF) XV277 on display at the National Museum of Flight, Scotland.
  • P.1127(RAF) XV278 on display at the Luftwaffenmuseum, Germany.
  • XV-6A Kestrel 64-18262
    United States military aircraft serials
    In the United States, all military aircraft display a serial number to identify individual aircraft. Because these numbers are located on the aircraft tail, they are sometimes referred to unofficially as "tail numbers"...

     on display at the National Museum of the United States Air Force
    National Museum of the United States Air Force
    The National Museum of the United States Air Force is the official museum of the United States Air Force located at Wright-Patterson Air Force Base northeast of Dayton, Ohio. The NMUSAF is the world's largest and oldest military aviation museum with more than 360 aircraft and missiles on display...

     at Wright Patterson AFB, Ohio, United States.
  • XV-6A Kestrel 64-18263 with NASA livery
    Livery
    A livery is a uniform, insignia or symbol adorning, in a non-military context, a person, an object or a vehicle that denotes a relationship between the wearer of the livery and an individual or corporate body. Often, elements of the heraldry relating to the individual or corporate body feature in...

     on display at the Virginia Air and Space Center
    Virginia Air and Space Center
    The Virginia Air and Space Center is a museum and educational facility in Hampton, Virginia that also serves as the visitors center for NASA's Langley Research Center...

    , Hampton, Virginia, United States
  • XV-6A Kestrel 64-18264 held in storage by the United States Army Aviation Museum
    United States Army Aviation Museum
    The United States Army Aviation Museum is an aviation museum located on Fort Rucker near Ozark, Alabama. It has the largest collection of helicopters held by a museum in the world. The museum features some 50 aircraft on public display with aviation artifacts ranging from a replica of the Wright...

    , Alabama, United States.
  • XV-6A Kestrel 64-18266 with NASA livery on display at Air Power Park
    Air Power Park
    The Air Power Park is an outdoor, roadside museum in Hampton, Virginia which recognizes Hampton's role in America's early space exploration and aircraft testing. The park is on a plot and includes a children's playground. There is no inside museum or visitor center Several vintage aircraft and...

    , Hampton, Virginia, United States.


Specifications (Kestrel FGA.1)

See also

External links

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