§ Mr. Maxwell-Hyslopasked the Minister of Aviation by what formula the thrust of jet engines, shaft horse-power and residual thrust of propeller-turbine engines, and shaft horse-power of piston engines are amalgamated into significant entries in the column headed, Index based on aero-engine power output, in table 89 of the Monthly Digest of Statistics.
§ Mr. StonehouseThe units of measurement concerned are: for reciprocating engines—brake horse-power; for turbojet and turbo-fan engines—pounds thrust; for turbo-driven propeller engines—shaft horse-power, and for turbo-propeller engines—equivalent shaft horse-power.
For the purpose of the index, brake horse-power, shaft horse-power and equivalent shaft horse-power are regarded as equivalents; to convert pounds thrust to the same equivalent, the pounds thrust is halved. Recent changes in engine types may have brought about a change in this latter relationship; the subject is under review.