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Aviation Accident

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NTSB Identification: ERA15LA291
14 CFR Part 91: General Aviation
Accident occurred Wednesday, July 29, 2015 in Winchendon, MA
Probable Cause Approval Date: 03/18/2019
Aircraft: SONTONASTASO MOSQUITO, registration: N285XE
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

According to the commercial pilot, about 1 hour into a local flight, he felt the helicopter suddenly "kick from loss of torque." He then observed that the engine rpm had dropped to about 30%, and he was unable to increase engine power using the throttle control. The pilot responded by performing an autorotation to an open field. During the landing, the helicopter touched down hard, and the main rotor system struck the tailboom, which resulted in substantial damage to the airframe and tail rotor drive system.
During a postaccident engine run, the pilot found that a faulty wiring crimp resulted in a loss of electrical power to the coil pack of one of the cylinders, which resulted in the engine experiencing a partial loss of power.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • A partial loss of engine power due to a faulty electrical wiring crimp in the engine‚Äôs ignition system.