On January 20, 2000, a Bell UH-1H (registration N853M) was involved in an aviation accident near Fort Myers, FL. Investigators recorded the probable cause as: Peak strain low cycle fatigue of the 2nd stage GP turbine disc. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot reported a loud bang and loss of engine power during a post-inspection flight. Investigation revealed the 2nd stage GP turbine disc fractured due to low cycle fatigue, leading to engine failure and a hard landing with rollover.
Incident Overview
During a post-inspection maintenance flight, the pilot reported that approximately 30 minutes into the flight, at an altitude of about 350 to 400 feet above ground level, a loud 'bang' was heard. Engine rpm immediately decayed to zero. The pilot chose an autorotation site that required using main rotor rpm to clear trees. The helicopter landed hard and rolled over.
Engine Examination
The T-53-L-13B engine was removed and subjected to a factory disassembly examination under FAA oversight. Material analysis determined that portions of the 2nd stage gas producer (GP) turbine disc had fractured and separated. The fracture was attributed to peak strain low cycle fatigue. This resulted in structural and imbalance damage, leading to engine failure. No material, lubrication, or fuel control defects were identified that would have contributed to the disc separation.
Probable cause
Peak strain low cycle fatigue of the 2nd stage GP turbine disc.
What happened in the 20 Jan 2000 Bell UH-1H accident near Fort Myers, FL?
A pilot reported a loud bang and loss of engine power during a post-inspection flight. Investigation revealed the 2nd stage GP turbine disc fractured due to low cycle fatigue, leading to engine failure and a hard landing with rollover.
What aircraft was involved and where did it happen?
The accident on 20 Jan 2000 involved a Bell UH-1H, registration N853M, at Fort Myers, FL.
What was the probable cause of the accident?
Peak strain low cycle fatigue of the 2nd stage GP turbine disc.
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