Pilot Debrief

BEECH B36TC near Lemoore, CA — 2011-08-14

Final reportWPR11LA380
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Date
2011-08-14
Location
Lemoore, CA, USA
Airport
NLC
Aircraft
BEECH B36TC
Registration
N6465X
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

A loss of engine power during cruise flight due to maintenance personnel's failure to adequately torque the number 4 cylinder retaining nuts, which resulted in the in-flight separation of the cylinder.

NTSB narrative

The pilot reported that, while at cruise altitude, the engine experienced a partial loss of engine power. The pilot requested to land, and then heard a loud noise, followed by the engine cowling opening, and the pilot noted something fly out of the engine compartment followed by a total loss of engine power. Unable to reach the airport, the pilot subsequently made a forced landing in a plowed field. Postaccident examination of the engine revealed that the number 4 cylinder and piston had separated from the engine in flight and likely departed through the open engine cowling. The crankcase had mechanical damage concentrated at the number 4 and 6 cylinder bay areas. The number 4 cylinder bay area had missing crankcase material, with rubbed and displaced material noted on the cylinder attachment area. Further examination of the remaining cylinders found that the retaining self-locking nuts were loose and had not been tightened or properly torqued. Review of maintenance records noted that the engine had been overhauled less than 40 flight hours before the accident. It is likely that maintenance personnel did not properly tighten the self-locking nuts for the number 4 cylinder, which subsequently led to its separation.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Regular maintenance checks could have identified engine issues before the flight.

NTSB coding

Evidence available

  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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