Product Improvement Test of UH-1( ) Symmetrical Engine-to-Transmission Drive Shaft
ARMY AVIATION BOARD FORT RUCKER AL
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The UH-1 engine-to-transmission standard drive shaft is being removed at an average of 532 flight hours, instead of achieving its time between overhaul of 1,100 hours. The major problem encountered is pitting of the splines. This condition is attributed to high operating temperatures, which result from high mission gross weights and combat-type maneuvering of the helicopter. The lubricant tends to deteriorate at the operating temperatures encountered, thus requiring inspection and lubrication of the shaft at 100- operating-hour intervals. In addition, the standard shaft can be easily installed backwards. If this happens, the shaft is not cooled properly and fails after a short operating time. In an attempt to increase the life of the shaft and to increase the inspection and lubrication intervals, the Iroquois Project Manager directed the test of an improved drive shaft. Primary differences between the new shaft and the standard shaft are a. Elimination of the cooling fin, allowing the shaft to be installed in either direction and still be properly cooled. b. Construction of splined couplings of new materials M50 tool steel and nitralloy N to provide better resistance to the high operating temperatures. c. Lubrication of the new shaft with Anderol L-786 FSN 9150-926- 1969, which is designed to withstand higher temperatures than the EP-2 lubricant formerly used.
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