OH-58 Helicopter Transmission Failure Analysis

The OH-58 main transmission gearbox was run at varying output torques, speeds, and oil cooling rates. The gearbox was subsequently run to destruction by draining the oil from the gearbox while operating at a speed of 6200 rpm and 36 000 inch-pounds output torque. Primary cause of gearbox failure was...

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Bibliographic Details
Main Authors: Townsend, D P, Coy, J J, Hatvani, B R
Format: Report
Language:English
Subjects:
AIR
ALUMINUM
BEARINGS
COOLING
DEFLECTION
DESTRUCTION
FAILURE
H-58 AIRCRAFT
Helicopters
Machinery and Tools
MATERIALS
MELTING
OH-58 AIRCRAFT
OIL COOLERS
OILS
OUTPUT
PLANETS
POWER
PRESSURE
RATES
RATINGS
STIFFNESS
STRESSES
TAKEOFF
TORQUE
TRANSMISSION GEARS
TRANSMISSIONS(MECHANICAL)
VELOCITY
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Description
Summary:The OH-58 main transmission gearbox was run at varying output torques, speeds, and oil cooling rates. The gearbox was subsequently run to destruction by draining the oil from the gearbox while operating at a speed of 6200 rpm and 36 000 inch-pounds output torque. Primary cause of gearbox failure was overheating and melting of the planet bearing aluminum cages. Complete failure of the gearbox occurred in 28 1/2 minutes after the oil pressure dropped to zero. The gearbox air/oil cooler has sufficient cooling capacity margin for hot day takeoff conditions at a 117 percent power rating. The alternating and maximum stresses in the gearbox top case were approximately 10 percent of the endurance limit for the material. Deflection of the bevel gear at 67 000 inch- pounds output torque indicate a marginal stiffness for the bevel gear supporting system.