Earlier sections have dealt with engines which have been developed almost entirely with the object of war and destruction. The fighter engine has been pushed all the time harder and harder to obtain greater output, with increased rate of supercharge, higher critical altitude, and more power to manœuvre under all possible conditions and attitudes of the aircraft. Performance has been achieved at almost any expense, provided reliability was ensured for a given period; such items as the time between overhaul and fuel consumption have been secondary considerations. In a similar way bomber engines have been continually stepped up in power to give maximum output at rich mixture for takeoff, so as to project the greatest possible load of bombs into the air, and every attention has also been given to providing the highest weak mixture cruising power at altitude, in order to allow for the necessary power to maintain flight at a reasonable altitude during the early part of the mission, when the machine is fully loaded.

This note is intended to cover the more interesting items of progress made since 1930 by the Fairey Aviation Company, Limited, in methods for ascertaining the relief centrifugal bending moments due to bending deflection in twisted propeller blades. Ref. 1 describes the only reliable method known to the writer in use at the commencement of this period. The first substantial change was made in 1932, when the time required to obtain a solution was reduced from over a week to about half a day without any considerable sacrifice in accuracy. Owing to independent research and the usual circulation of junior staff the 1932 method is now fairly widely known under various names, but this note would be incomplete without its inclusion as it forms the basis of subsequent methods. The convergence by this method is not very rapid as it only halves the error at each successive approximation. An alternative method reducing the error to about one-tenth at each step is also given.