A.P. 129 RAF Flying Training Manual, Part I - Landplanes

[Crumpp]

A override for take-off is linked to extra rich mixture to preventing detonation.

Exactly. It was used to test the engine at altitude during service maintenance.

THAT IS WHY YOU HAVE PILOT ANECDOTES OF FLYING AT +16 LBS ON 87 OCTANE!

If they tested the engine to 10.5lbs then a low engineering safety factor of 1.6 yields 16.8lbs. That pilot who did that was extremely lucky his engine did not destroy itself from detonation.

AIR MINISTRY
Air Publication 129
Revised November 1937
Royal Air Force
FLYING TRAINING MANUAL
Part I - LANDPLANES
Chap. II
Aero-engine speeds and boost pressures
66. (vi).(c). Aircraft should not be flow at the maximum conditions for level flight except in emergency, or when special operational conditions necessitate it.