A revetment, in military aviation, is a parking area for one or more aircraft that is surrounded by blast walls on three sides. These walls are as much about protecting neighbouring aircraft as it is to protect the aircraft within the revetment. If a combat aircraft fully loaded with fuel and munitions was to somehow be set on fire, by accident or design, then it could start a chain reaction, as the destruction of individual aircraft could set ablaze its neighbours. The blast walls around a revetment are designed to channel blast and damage upwards and outwards away from neighbouring aircraft.
A blast pen was a specially constructed E-shaped double bay at British RAF World War 2 fighter stations, being either 150 feet (46 m) or 190 feet (58 m) wide and 80 feet (24 m) front-to-back, accommodating aircraft for safe-keeping against bomb blasts and splinters during enemy air-attacks.
Although the pens were open to the sky the projecting sidewalls preserved the aircraft from lateral damage, with 12-inch (300 mm) thick, 9 feet (2.7 m) high concrete centres, and banked-up earth on either side, forming a roughly triangular section 18 feet (5.5 m) wide at their base. The longer spine section behind the parking areas usually encloses a narrow corridor for aircrew and servicing personnel to use as an air raid shelters.
Examples may still be seen at the present Kenley Aerodrome and at North Weald Airfield close to "The Squadron" bar, some pens have had their second bay removed over the years, thus becoming U-shaped.There are also a large number at the former RAF Catterick by the A1, and some at RAF Wittering. The Imperial War Museum Duxford has one that is accessible to the public. Whilst common on Fighter Command airfields, other RAF Stations such as RAF Benson and RAF Brize Norton did not have any blast pens.
- Refuelling and rearming a Spitfire Mark VC(T), in a revetment constructed from empty fuel tins filled with sand at RAF Ta Kali, Malta in 1942
- A destroyed US Air Force Lockheed C-130 Hercules in Vietnam, c. 1967
- Flint, Peter (1985). R.A.F. Kenley. Terence Dalton Limited. p. 158. ISBN 0-86138-036-3.