Schweizer 269C N521AR accident near Coolidge, Arizona

Probable cause

A partial loss of engine power due to separation of the throttle cable.

NTSB analysis

The private pilot stated that the helicopter was in cruise flight when he noted a change in engine sound and a corresponding loss of engine rpm. He checked the throttle to ensure that it had not rolled back; it had not. He then attempted to roll the throttle on, then off; however, there was no response from the engine. The pilot chose to perform a precautionary landing, during which the helicopter landed hard and rolled over.

Postaccident engine examination revealed that the throttle arm at the fuel injector servo would not move when input was applied at the collective throttle grip; the cable had separated within its housing. The cable housing was securely mounted at each end and exhibited no evidence of damage. The cable was removed from the housing; it was worn and had separated near the servo end about 1 inch from where it swaged to the rigid portion in an area where the cable housing was slightly bent. This bend in the housing likely resulted in the cable rubbing on the interior housing wall and, over time, led to the cable's the failure and separation, and the subsequent partial loss of engine power. Examination of the helicopter maintenance logs did not provide a history of the cable maintenance; however, the cable was not subject to any hourly or calendar life limits, and there was no way to disassemble the housing to facilitate an internal examination of the cable. The cause of the bend in the housing could not be determined.

Text from the NTSB. Open the NTSB docket for WPR17LA093 for the full record.