Pilot Debrief

MCDONNELL DOUGLAS HELI CO 369FF near Wikieup, AZ — 2018-05-29

Final reportWPR18LA152
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Date
2018-05-29
Location
Wikieup, AZ, USA
Aircraft
MCDONNELL DOUGLAS HELI CO 369FF
Registration
N975BW
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

A vibration of the helicopter for reasons that could not be determined based on the available information, which resulted in a forced landing and the main rotor contacting the tailboom.

NTSB narrative

The pilot was performing external load operations in the helicopter when he felt a vibration during a left descending turn. The pilot increased the collective to arrest the rate of descent, but the vibration became more prominent. He subsequently performed a forced landing, during which the helicopter impacted the ground and a main rotor blade contacted and severed the tailboom. The pilot did not report any malfunctions with the engine nor any abnormal increase or decrease in main rotor rpm. Postaccident examination revealed a fractured drive link and a fractured strap pack assembly. Examination of the fractured surfaces revealed signatures consistent with tensile overstress, most likely from the blade contacting the left inlet fairing after the helicopter impacted the ground. There was no other evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation, and the reason for the vibration could not be determined based on the available information.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have aborted the maneuver when vibration first occurred.

NTSB coding

Evidence available

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

Docket documents8

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MCDONNELL DOUGLAS HELI CO 369FF near Wikieup, AZ — 2018-05-29 · Pilot Debrief