Pilot Debrief

SONEX LIMITED WAIEX near Fond du Lac, WI — 2016-08-03

Final reportCEN16LA302
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Date
2016-08-03
Location
Fond du Lac, WI, USA
Airport
FLD
Aircraft
SONEX LIMITED WAIEX
Registration
N12YX
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Initial climb

Probable cause

A partial loss of engine for reasons that could not be determined during an examination of the engine.

NTSB narrative

Shortly after takeoff on an instructional flight, the pilots heard a sudden change in engine noise. The instructor scanned the engine instruments and observed that the engine rpm was lower than expected. The instructor took control of the airplane and attempted to return to the airport. The airplane was not able to maintain altitude, and the instructor could not restore engine power to full. Unable to reach the airport, the instructor initiated a forced landing to a field. During the approach, the airplane collided with a power transmission line and impacted terrain. An examination of the engine found that the Nos. 1 and 2 exhaust valves displayed excessive wear. While such wear will result in a loss of engine power, it could not be determined what caused the sudden change in noise and engine power that the pilots experienced on the day of the accident.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted takeoff upon hearing engine noise change.

NTSB coding

Evidence available

  • 4 docket documents
View NTSB final reportView NTSB docket

Docket documents4

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