HEADQUARTERS:
         AIR DEFENCE GREAT BRITAIN.
                 ROYAL AIR FORCE
                         BENTLEY PRIORY
                                 STANMORE
                                         MIDDLESEX
 18th September 1944.

Use of 150 Grade Fuel

Sir,

        I have the honor to refer to the above subject, and state that during the last 6 months a considerable amount of experience has been gained in A.D.G.B. with the use of 150 Grade Fuel in operational aircraft. The use of this fuel allowed higher boost pressures, which gave substantial increases in aircraft performance, and these increases were of great value when Squadrons of A.D.G.B. were employed against the flying bomb. Attached at Appendix A is a summary of the experience gained.

2.        Because the flying bomb menace no longer exists, and because under existing operational commitments, aircraft of A.D.G.B. will have to refuel at landing grounds in Belgium or Holland, it has been decided to revert to the use of 130 Grade Fuel and to adjust engines to their previous maximum boost pressure. To continue to use 150 Grade Fuel in operational Squadrons is undesirable for the following reasons:-

(i)The free interchange of Squadrons with T.A.F would be complicated in that aircraft would have to be modified for the lower boost pressure on transfer.
(ii)To use 150 Grade Fuel when operating from U.K and to use 130 Grade Fuel when refueling on the Continent, would call for repeated adjustments of the maximum boost pressure obtainable.
(iii)The increased performance obtainable by the use of 150 Grade Fuel is not an essential operational requirement for the role, which A.D.G.B. Squadrons will be called to undertake in the near future.
(iv)The supply of 150 Grade Fuel is such that stocks can only be laid down a certain airfields. This imposes a degree of inflexibility, which is undesirable.
(v)The use of high boost pressures in Mosquito aircraft calls for the fitting of open exhausts as the night flying exhausts will not withstand the temperatures associated with the higher boost pressures. Therefore, to continue to use the higher boost pressures in Mosquito aircraft makes the aircraft unsuitable for normal Night Fighter operation.

The Air Officer Commanding-in Chief,
Headquarters
Allied Expeditionary Air Force.