By late 1961, Hawker had been able to demonstrate the validity of its design concept, despite a lack of support from the RAF and little from the Her Majesty's Civil Service.
In early 1962, official support emerged in the form of the Operational Requirements branch of the Ministry of Aviation, which approached the Treasury seeking its sanction of a batch of nine production-standard aircraft to be operated by an evaluation unit to be administered by the Central Fighter Establishment at RAF West Raynham.
In light of open interest expressed by figures within the U.S. and West Germany, the British government approached these nations with an offer to collaborate on the project and to seek contributions towards the cost involved.
Following the acceptance of all three nations, on 22 May 1962, Hawker received a formal Instruction to Proceed with the procurement of materials for the construction of the nine aircraft.

The nine aircraft were ordered as the Kestrel FGA.1, which was essentially an improved version of the P.1127.
On 7 March 1964, XS688 became the first Kestrel to conduct its maiden flight, flown by Bill Bedford.
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, in addition to some other changes, such as addition of ultra high frequency (UHF) radio and assorted operational equipment in a bay house within the rear fuselage.
Prior to the availability of the Kestrel for testing, a pair of NASA pilots visited Dunsfold to perform a complete set of handling trials using the earlier P.1127 in its place.

On 15 October 1964, the Tri-partite Evaluation Squadron (TES) was formed at RAF West Raynham, staffed by a diverse mix of military test pilots from Britain, the United States and West Germany.
The personnel comprising the squadron were highly experienced pilots; prior to flying the Kestrel, each received a week's ground training at Bristol's in-house facility and a week's ground instruction at Dunsfold prior to a three-hour flight conversion instructed by Bill Bedford.
The purpose of the squadron was to evaluate the suitability of V/STOL aircraft for field operations, compare competing styles and methods of taking off/landing, develop normal flight operating procedures, perform instrument flight assessments, conduct night flight operations, and explore jet-borne maneuvering throughout the Kestrel's flight envelope.

During the course of the evaluation, the Tri-partite 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) was judged to be the optimal practice.
Operating from rough airstrips was also trialled at nearby RAF Bircham Newton, 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 when a pilot tried to do a rolling take-off with the parking brake on; 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, 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 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 on boar
By late 1961, Hawker had been able to demonstrate the validity of its design concept, despite a lack of support from the RAF and little from the Her Majesty's Civil Service. In early 1962, official support emerged in the form of the Operational Requirements branch of the Ministry of Aviation, which approached the Treasury seeking its sanction of a batch of nine production-standard aircraft to be operated by an evaluation unit to be administered by the Central Fighter Establishment at RAF West Raynham. In light of open interest expressed by figures within the U.S. and West Germany, the British government approached these nations with an offer to collaborate on the project and to seek contributions towards the cost involved. Following the acceptance of all three nations, on 22 May 1962, Hawker received a formal Instruction to Proceed with the procurement of materials for the construction of the nine aircraft.
The nine aircraft were ordered as the Kestrel FGA.1, which was essentially an improved version of the P.1127. On 7 March 1964, XS688 became the first Kestrel to conduct its maiden flight, flown by Bill Bedford. 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, in addition to some other changes, such as addition of ultra high frequency (UHF) radio and assorted operational equipment in a bay house within the rear fuselage. Prior to the availability of the Kestrel for testing, a pair of NASA pilots visited Dunsfold to perform a complete set of handling trials using the earlier P.1127 in its place.
On 15 October 1964, the Tri-partite Evaluation Squadron (TES) was formed at RAF West Raynham, staffed by a diverse mix of military test pilots from Britain, the United States and West Germany. The personnel comprising the squadron were highly experienced pilots; prior to flying the Kestrel, each received a week's ground training at Bristol's in-house facility and a week's ground instruction at Dunsfold prior to a three-hour flight conversion instructed by Bill Bedford. The purpose of the squadron was to evaluate the suitability of V/STOL aircraft for field operations, compare competing styles and methods of taking off/landing, develop normal flight operating procedures, perform instrument flight assessments, conduct night flight operations, and explore jet-borne maneuvering throughout the Kestrel's flight envelope.
During the course of the evaluation, the Tri-partite 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) was judged to be the optimal practice. Operating from rough airstrips was also trialled at nearby RAF Bircham Newton, 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 when a pilot tried to do a rolling take-off with the parking brake on; 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, 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 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 on boar
Hawker Siddeley P.1127