Pilot Debrief

MOONEY M20E near Marked Tree, AR — 2012-07-21

Final reportCEN12FA463
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Date
2012-07-21
Location
Marked Tree, AR, USA
Airport
6M8
Aircraft
MOONEY M20E
Registration
N1310W
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Cruise

Probable cause

The loss of engine power during cruise flight due to a malfunction of the fuel injection servo due to a damaged O-ring.

NTSB narrative

The pilot reported that about 5 minutes after reaching cruise altitude, the engine started to run rough with an accompanying partial loss of power. He noted that the engine exhaust temperatures had dropped but that other engine indications were normal. The pilot elected to divert to an intermediate airport; however, the engine continued to lose power, and the pilot was unable to maintain a proper glide path to the runway. The pilot was concerned about an inadvertent aerodynamic stall, so he made a forced landing to the bean field short of the runway. Postaccident bench testing of the engine fuel injection servo revealed variations in fuel flow that were not consistent with normal servo operation. Further examination of the fuel servo revealed that the mixture control valve O-ring was damaged and that a fragment of the O-ring was located on the surface of the mixture control valve plate. This likely interfered with fuel flow through the servo and reduced the available engine power. The fuel servo was overhauled about 1 year before the accident and had accumulated about 113 hours in service since the overhaul.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have diverted earlier when engine started to run rough.

NTSB coding

Evidence available

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

Docket documents8

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