Engine running pens – Listed Grade II

Three pens were arranged in a curve. One has been completely removed. Of the two remaining; the unique example survives that was used to test all ‘jump jets’ or VTOL. The VTOL pen is lined with metal sheeting and sound absorption. Historical significance is for the development of the ‘jump jet’, P1127 through to the Harrier.

In 2022 aerial views you can see the remaining two pens plus the site of the third to the West.

Three engine running or detuning pens were originally built in the early 1950’s to test the aircraft engines for the Hunter prior to delivery. By 1960 the Eastern-most of the three pens was modified specifically for engine testing of the P.1127 and later the Harrier. This pen was modified and excavated to form a void which was fitted with a blast grid to diffuse vertical thrust. At the rear of the pen, a new diffuser was fitted to contain thrust when the engines were vectored to the rear. At the same time, a second control room was added and the inside of the pen was fitted out with metal covered insulation. A double-depth metal sliding door was also installed at the entrance so that when closed, noise and debris were suppressed.

As CTP Bill Bedford recounted, in 1960 when undertaking the first testing of the engine for the prototype P.1127 there was an engine fire. The “elephant ears” noise baffles either side of the aircraft had to be rapidly moved out of the way to allow fire crew to access the exhaust to dowse the fire.

The first P.1127, XP831, in the ground running pen at Dunsfold with Rolls-Royce representative John Vowles in the cockpit.  Photo courtesy BAE Systems via Brooklands Museum
Pen Construction 1960’s: BAE Systems via Brooklands Museum
Hawk 200 in Engine Running Pen (1980s) (courtesy Brooklands Museum archive)
Engine Pen exhaust. Photo Alec Bryan
Engine running pens
Harrier ZB604 in the engine pen.

The two engine running pens were given Grade II Listed Building status in December 2017.  Historic England’s detailed Listing report


Since application for a Conservation Area and Waverley Borough Council’s rejection there have been a number of assets considered for Listed Building Status.  Historic England have since designated 5 Listed Structures on the Airfield site:

Primemeads Farm – Grade II

VTO Blast Pads – Grade II

Engine Running Pens – Grade II

Royal Observer Corps Monitoring Post – Grade II

Canadian War Memorial – Grade II


Please note: The aerodrome is private land and an active airfield. Access is not permitted to some of the buildings and features and we strongly discourage access without permission.

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