Pilot Debrief

LUSCOMBE 8A near Cowiche, WA — 2011-08-18

Final reportWPR11LA391
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Date
2011-08-18
Location
Cowiche, WA, USA
Airport
YKM
Aircraft
LUSCOMBE 8A
Registration
N1444K
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

A partial loss of engine power during maneuvering flight due to an exhaust valve failure.

NTSB narrative

During a training flight, the airplane's occupants heard a hammering sound accompanied by an airframe vibration and reduction in engine power. The certified flight instructor took control of the airplane from the student and began to initiate a return to the airport. He decided that it was unlikely that they would be able to safely return, and he elected to perform a forced landing into a field. The airplane landed hard. Examination of the engine revealed that the exhaust valve head most likely separated from its stem during flight, resulting in catastrophic failure to its associated cylinder components. Discoloration within the rocker area, exhaust valve guide, and cooling fins was consistent with heat damage, most likely caused by a stuck or sticking exhaust valve. The engine was manufactured in 1948, and its serial number did not match any records on file with the manufacturer. The maintenance records did not reveal a complete history of the engine's total flight time.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
CFI could have opted for an immediate return to Yakima upon hearing the hammering sound.

NTSB coding

Evidence available

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

Docket documents8

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