Pilot Debrief

Cessna 150 near Madison, SD — 2018-08-14

Final reportCEN18LA329
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Date
2018-08-14
Location
Madison, SD, USA
Airport
MDS
Aircraft
Cessna 150
Registration
N6341K
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

A stuck No. 3 cylinder exhaust valve, which resulted in failure of the associated rocker arm, a partial loss of engine power, and the subsequent forced landing into tall vegetation.

NTSB narrative

The student pilot reported that he was flying north of the departure airport when the airplane's engine began running roughly. He attempted to return to the airport but was unable to reach the airport and landed in a cornfield. The airplane nosed over in the 7-ft-tall corn and sustained substantial damage to both wings. Examination of the airplane revealed that the engine's No. 3 cylinder exhaust valve was stuck in its valve guide, and the No. 3 exhaust valve rocker arm was fractured. A maintenance record entry indicated that the Nos. 1, 3, and 4 cylinders had experienced valves sticking and had been sent back to the overhaul vendor for service. The cylinders were reinstalled 3 days before the accident. Based on the available evidence, the partial loss of engine power was likely due to the No. 3 cylinder exhaust valve becoming stuck, which resulted in a secondary overload failure of the associated rocker arm and a substantial reduction in engine power output.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have conducted a precautionary landing before engine failure worsened.

NTSB coding

Evidence available

  • 2 docket documents
View NTSB final reportView NTSB docket

Docket documents2

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