T40 DEVELOPMENT HISTORY
In 1945, the requirement for engines of higher power, lower weight, and smaller size, to improve the performance of propeller driven aircraft lead the U.S. Navy to request all the major engine companies to submit proposals for a turboprop engine development. The Allison Division of General Motors Corporation proposed development of an engine featuring twin power sections, permitting operation of only one power section for optimum performance at cruise power, and contrarotating propellers to cancel propeller torque reaction. The development of this engine, the T40, was initiated in December 1945 and a three year period was allocated for its development. The fallacy of this timing can now be seen and a development of this nature today would be assigned a six or seven year period, but at that time when little was known about turbine engines, a three year period seemed realistic.
This optimistic schedule became of extreme importance when several air-craft programs were committed to the T40 engine with engine availability based on this unrealistic development timing. As the basic development began to lag, the need for flight engines for the committed aircraft models remained constant. To avoid large delays in aircraft scheduling it was thus necessary to attempt to provide some type of flight engines, even though extremely prematurely. This caused diversion of basic development effort and extended the development program. As the program lagged, more interim engines were needed and the cycle repeated itself. Delay and lack of attention to the basic engine development were the obvious results of being caught in this situation. The contractor's inability to expand his staff adequately to rectify this situation is also considered contributory as regards the delay experienced. Because of the above, the T40 did not successfully complete the 150-hour qualification test until December 1953. By that time the XA2J aircraft program had been terminated and the A2D had been reduced to a token program. The latter was subsequently completely terminated in September 1954. The R3Y remains T40 powered as do the two vertical take-off aircraft, the vertical T40 engine having been developed as a modification of the qualified engine.
In summary, the failure of the T40 to meet its development goal on time and the consequent disruption to associated aircraft programs stemmed from a lack of appreciation of the time and effort required to develop such an engine, coupled with extensive aircraft scheduling based on early engine availability.