Pilot Debrief

SONTONASTASO MOSQUITO near Winchendon, MA — 2015-07-29

Final reportERA15LA291
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Date
2015-07-29
Location
Winchendon, MA, USA
Aircraft
SONTONASTASO MOSQUITO
Registration
N285XE
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

A partial loss of engine power due to a faulty electrical wiring crimp in the engine’s ignition system.

NTSB narrative

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.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Identifying and fixing the bad crimp in the ignition system before flight.

NTSB coding

Evidence available

  • Photos
  • 4 docket documents
View NTSB final reportView NTSB docket

Docket documents4

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