Pilot Debrief

CESSNA 172 near Skwentna, AK — 2021-07-16

Final reportANC21LA061
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Date
2021-07-16
Location
Skwentna, AK, USA
Aircraft
CESSNA 172
Registration
N7137T
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Takeoff roll

Probable cause

A partial loss of engine power due to detonation/preignition damage to the No. 2 cylinder. The reason for the detonation/preignition damage could not be determined based on the available evidence.

NTSB narrative

The pilot reported that during takeoff from an off-airport gravel bar on a river, the airplane experienced a partial loss of engine power. The pilot rejected the takeoff, and the airplane subsequently encountered a “bump,” which pitched the nose down. The pilot then made a hard right turn to avoid going into the water, and the airplane nosed down and impacted the ground with the left wing, which resulted in substantial damage to the left wing. Postaccident examination revealed that the No. 2 cylinder would not produce compression. Removal of the No. 2 cylinder revealed damage, including a hole in the piston that was consistent with detonation and/or preignition. The reason for the detonation and/or preignition could not be determined based on the available evidence.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have chosen to abort takeoff earlier after initial power loss.

NTSB coding

Evidence available

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

Docket documents5

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