Robinson Helicopter R22 BETA N115DD accident near Cahokia, Illinois

Probable cause

The pilot’s poor decision to take off with the clutch warning light illuminated, which resulted in the total failure of the fan assembly due to a lack of lubrication. Contributing to the accident was the mechanic’s failure to lubricate the lower actuator bearing at the last annual inspection.

NTSB analysis

The pilot reported that the helicopter's clutch warning light illuminated shortly after departure, which he did not think was abnormal because, when the belts heat up and re-tension, it causes the light to briefly illuminate; this was corroborated by the Pilot's Operating Handbook (POH). He continued the takeoff and then watched to see if the light would go out in 10 seconds. However, the POH stated that a pilot should never take off before the clutch warning light goes out. The light did not turn off, so he pulled the clutch circuit breaker and chose to land immediately in a parking lot. After landing, the pilot locked the controls, got out of the helicopter, and looked inside the engine compartment, but he did not see anything abnormal. The pilot said that he did not feel safe in his surroundings, so he chose to get back in the helicopter and make the short flight back to the airport. The pilot then departed and was about 500 yards from landing at the airport when the helicopter began to vibrate and make noise. The pilot initiated an autorotation, but, as he slowed and flared the helicopter, it yawed left as he pulled on the collective. The skids contacted and then dug into the soft ground, and the main rotor blades severed the tail boom. It is likely that the accident could have been prevented if the pilot had not taken off after the clutch warning light illuminated or if he had turned back and landed at the airport after the warning light did not extinguish.

A postaccident examination of the helicopter's fan assembly, including the lower sheave and lower actuator bearing, revealed no evidence of lubrication and heat damage, consistent with a lack of lubrication. The helicopter had undergone an annual inspection about 9.1 hours before the accident. Although the mechanic who performed the last annual inspection made an entry in the engine logbook that he lubricated the lower actuator bearing, it is likely that he did not perform that task given the lack of lubrication on the bearing.

Text from the NTSB. Open the NTSB docket for CEN14LA517 for the full record.