V/STOL blast grid at Dunsfold airfield, Dunsfold, Surrey

Summary

Steel V/STOL blast grid of 1960, located at the western end of the main runway at Dunsfold airfield.

Description

Steel V/STOL blast grid of 1960, located at the western end of the main runway at Dunsfold airfield.

MATERIALS: boxed-steel, brick, concrete and steel-plate.

PLAN: the grid is rectangular and measures approximately 10m by 20m. The longer edge faces broadly east-west along the main runway.

DESCRIPTION: for safety reasons, the grid is now completely covered with sections of steel-plate, but it is likely that the below ground structure survives. The following description is based on photographs taken during construction; the blast grid is sunk around 2m into the tarmac runway surface and is formed of multiple steel box-sections of approximately 0.5m by 1m, which are supported by steel uprights of circa 1.5m in height. Within each box-section there is a curved metal vane designed to disperse exhaust gases into the void below. The void is formed by brick walls and a concrete floor. To the centre of the grid there is an inset lifting door of finer box-section measuring approximately 2m by 3m, which probably provides access for maintenance to the underside of the grid.

History

The V/STOL (Vertical/Short Take Off and Landing) blast grids were built to support the development of a V/STOL fighter aircraft during the early 1960s at Dunsfold airfield.

The airfield was constructed for the military in 1942, by Royal Canadian Engineers. Initially it was home to four squadrons of Tomahawks and Mustangs, tasked with training and reconnaissance. By August 1943 it had become a bomber base, supporting Mitchell bombers on European missions, and by 1944 the airfield had three runways and accommodation for over a 1,000 personnel.

In the early 1950s Hawker Siddeley were developing jet aircraft for which the short, grass landing strips then available to them, were insufficient. Long hard-surfaced runways were required and Dunsfold was identified as a base which could work hand in hand with their existing factory in Kingston, Surrey. This was a period of consolidation for the many private British aircraft companies, and with the benefit of Britain’s lead in jet engine technology, these newly consolidated companies had the financial wherewithal and technical capability to lead the world in jet aviation. During the 1950s and 1960s, huge advances were made and for this brief period of time, Britain led the world in this area.

On taking over Dunsfold airfield, Hawker Siddeley developed a final assembly and experimental test facility including engine running pens to test the jet engines in the aircraft prior to delivery. The first aircraft to be developed and assembled at Dunsfold was the Hunter which at the time was at the cutting edge of military jet fighter development, and first took to the air in 1951. Flown by Squadron Leader Neville Duke, it later broke the world speed record achieving a speed of 727.6 mph on the 7 September 1953. Hunters were put into service by the Royal Air Force (RAF) in 1954, and after a number of teething problems, were in operational use until the 1990s.

By the start of the 1960s, the company was developing the concept of V/STOL which involved the use of vectored thrust to lift a static or slow moving aircraft in to the air. Once airborne, the engine thrust would be transitioned to the rear and the aircraft would achieve normal forward flight. Hawker Siddeley recognised a need for a fighter that could be operated away from large airfields, therefore reducing dependence on fixed airfields that were vulnerable to nuclear attack. On 15 July 1960, the first P1127 Prototype V/STOL Strike Aircraft serial XP831, was delivered to Dunsfold airfield to commence static engine testing in the engine running pens. On 31 August 1960, the Pegasus engine was run for the first time while inside the aircraft.

Early testing of the concept was performed from the purpose-built V/STOL blast grid, which was located at the western end of the main runway. This was a new technology and the physics of vectored thrust were not fully understood. The grid was designed to deflect the hot exhaust gases away from the hovering aircraft, and protect the runway tarmac. It was also thought to be essential in eliminating the adverse effects of thrust losses due to re-ingestion of these hot gases, which was important as the thrust of the prototype engine was only adequate to lift the aircraft with a small fuel load, and all non-essential equipment removed. The designers were also concerned that the aircraft might depart controlled flight in the hover, so tethering points and lines were added to the grid, so that it could be held back in an emergency. Initially the tethers were set at a length of 1ft, and the first hover in this configuration was achieved by Bill Bedford on the 4 November 1961, with one of his legs still in plaster from an earlier car accident. Later, when the tethers were lengthened to 4ft the reaction controls of the aircraft were found to be inadequate. When the aircraft departed from the ground, it had a tendency to lift one wing ahead of the other, and there was too little roll-power within the controls to correct this. This lack of control caused the aircraft to 'cavort around like a drunken cow', until the controls were modified. The first free hover occurred on 19 November. In parallel, conventional taxi-trials were performed at speeds of up to 70 knots. Finally, on 13 February 1962, the first conventional flight was achieved.

The P.1127 evolved into the Kestrel and then the Harrier. By 1969, the RAF was using Harriers operationally, and by 1980 the Sea Harrier variant was in use by the Royal Navy. Harriers saw action as part of the Falklands Task Force in 1982, operating from the carrier HMS Hermes some 8,000 miles from England. They flew 1,435 operational sorties, accounting for the destruction of 28 enemy aircraft, with no losses in the air. The Harrier went on to become probably the most successful British military aircraft to date, with 112 sold to the US Marine Corps. In total 879 aircraft were built at Dunsfold with an estimated sales value of £2.6 billion (2017 values).

The V/STOL blast grid has been covered over with steel-plate but is believed to be otherwise intact. Two other larger steel-sheeted blast platforms (one to each end of the runway) were constructed in the 1970s, and were probably used for tests that would have otherwise harmed the runway tarmac.

Reasons for Listing

The western 1960s V/STOL blast grid at Dunsfold airfield, designed to test the V/STOL prototype in the hover, is listed at Grade II for the following principal reasons:

Historic interest:

* For its essential role in the testing of the V/STOL prototype which was the precursor to the Harrier jump jet, which went on to arguably be the nation's most successful late-C20 military combat jet aircraft;

* The hover grid is probably unique and can be considered to be the epicentre of V/STOL development in England;

* Associative value with the preparation for the Cold War as V/STOL was designed to allow operation from remote sites, rather than major airfields which were likely to be lost during a nuclear attack.

Architectural interest:

* The V/STOL blast grid through its technological structure is able to show how facilities were designed for the specialised needs of leading-edge V/STOL aviation testing.

Group value:

* With the engine running pens, the V/STOL blast grid forms an important group of structures at Dunsfold, which are directly related to the creation, testing, and manufacture of the iconic Harrier jump jet;

* With the Grade II listed 1942 airfield memorial and the Royal Observer Corps observation post.

External Links

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