Pilot Debrief

Robinson R44 near Westminster, MD — 2018-09-30

Final reportERA18LA269
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Date
2018-09-30
Location
Westminster, MD, USA
Airport
NONE
Aircraft
Robinson R44
Registration
N440SH
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Ground

Probable cause

The pilot's attempt to move the helicopter from a sloped surface after an overspeed event, which resulted in a loss of helicopter control and impact with a car. The overspeed event resulted from misrouted and damaged wiring in the magneto, which subsequently resulted in errant and random signals to the governor.

NTSB narrative

The commercial pilot stated that, during takeoff, the helicopter experienced an engine and main-rotor overspeed and that he then conducted a precautionary landing on a down-sloping portion of a parking deck. Skid marks indicate that only the toes and tails of the landing gear's skids contacted the deck upon landing rather than the full length of each skid tube. The pilot disembarked the passengers and then "attempted to reposition the helicopter to its original spot." He "increased the throttle to return to normal engine rpm," but the helicopter "started spinning uncontrollably." As the helicopter rotated around its mast, the owner/operator, who was standing beside the helicopter, ducked to avoid the tailboom before it struck a parked car. The pilot said that he stopped the engine and the helicopter's rotation by pulling the mixture control. The tail rotor blades and vertical stabilizer sustained substantial damage. During a test run of the helicopter, when the engine was operating in the governed range, an engine overspeed occurred, similar to that described by the pilot. When the engine was operating with the governor in the "off" position, the engine rpm was controllable with no anomalies noted. Disassembly of the magneto that sent the signal to the governor controller module revealed that the wiring was misrouted and damaged, which resulted in errant, random signals to the governor and the subsequent loss of helicopter control.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have opted to use ground-handling wheels instead of attempting to reposition the helicopter.

NTSB coding

Evidence available

  • Video
  • 15 docket documents
View NTSB final reportView NTSB docket

Docket documents15

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