The crankcase top cover, in spite of its apparent simplicity, presents many difficult machining problems. This installment deals mainly with special fixtures introduced by de Havilland engineers to overcome them and also ensure interchangeability.

This article first appeared in the Volume 6, Number 74 (December, 1944) issue of Aircraft Production magazine, and is presented here through the kind permission of Flight International. Thanks also to Bruce Vander Mark for furnishing volumes of Aircraft Production for scanning.