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OH-6A Tail Rotor Transmission Grease Evaluation and Fail Detection System Test

Hughes Helicopters has conducted tests to evaluate the effectiveness 
of MCG-68—63 heavy load, anti—wear grease in the OH-6A and OH-58 
tail rotor transmissions and to test a fail detection system installed 
on the OH-6A tail rotor transmission. 
TWO OH-6A tail rotor transmissions were spectrum load tested for 200 
hours each. Temperature measurements of the bearings, case, and 
gear teeth for the grease-filled transmission were higher than those 
obtained with oil as a lubricant. A no-load dynarnic torque test 
for the transmission Which vas filled to 98 percent Of grease capacity 
revealed the torque to be approximately four times the value demon- 
St rated Vhen the t Vas filled With Oil. 
The OH I Oad tested for hours . 
test results Vere simi lar to those obtained with the OH-6A transmission, 
except that the temperature changes were less. Excessive wear and 
scoring of the OH-58 transmission gear teeth was noted as a result of 
the test. 
The fail detection system vas tested using MCG-68-63 grease in the 
OH—6A t ransmission. The system, as tested, did not reliably display 
the induced failure modes simulated in the test. 
The MCG-68-63 grease may be an acceptable lubricant for the tail 
rotor transmissi on. An advantage realized for war-time operation 
is the slow rate of grease Loss through a hole approximately 3/4 inch 
in diameter enabling at least a one hour "get-hr-me" capability.

rhe work documented in this report vas performed by Hughes Helicopters, 
Division of Stmuna Corporation, Culver City, California for the U.S. 
Amy Aviation Systems Com•.and, St. Louis, Missouri under Delivery 
Order NO. 0019 Of Engineering Services Contract 
The Were at the Hughes i COP St Test 
labo ratory. from September 1972 through February 1976.