Try the following book:
Observers and Navigators and Other Non-Pilot Aircrew in the RFC, RNAS and RAF
by Wing Commander C. G. Jefford
Part I traces the rise of the first generation of non-pilot aircrew, the observers, aerial gunners/gunlayers and kite balloon observers who flew with the RFC, RNAS and latterly the RAF between 1914 and 1919.
Part II examines the way in which the peacetime RAF rapidly dispensed with its observer officers and spent the next fifteen years attempting to make do by misemploying airmen as air gunners on a part-time basis. This inadequate practice is contrasted with the very positive attitude towards non-pilots that prevailed within the Royal Navy. The story continues with the reinstatement of observers in 1934, albeit still as part-time corporals until 1939. Wartime experience soon revealed that the omnipotence of pilots was a myth and by the summer of 1940 all observers and gunners were at least sergeants and increasing numbers were being commissioned. Part II goes on to examine the proliferation of non-pilot aircrew categories until 1942 when the system was substantially reorganised, the observer being supplanted by the air bomber and a variety of specialised types of navigator. This section ends with a summary of wartime training.
Part III covers the rest of the century, including the last two years of WW II and the ill-conceived '1946 Aircrew Scheme'. Following the latter's demise in 1950, the RAF adopted an all-officer policy for its pilots and navigators, the fact that they were to have equal career prospects having been announced as early as 1948. Part III examines the way in which this policy of equality has actually been applied while continuing to trace the rises and falls in the fortunes of all non-pilot categories to date.
What emerges, along with a much clearer impression of the crucial importance of non-pilots to the RAF, is a discriminatory attitude towards them. The author demonstrates that this attitude had its roots in the RFC where it became so institutionalised that its effects are still detectable today.