NTSB Identification: CEN12FA463
14 CFR Part 91: General Aviation
Accident occurred Saturday, July 21, 2012 in Marked Tree, AR
Probable Cause Approval Date: 02/14/2013
Aircraft: MOONEY M20E, registration: N1310W
Injuries: 1 Minor,1 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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

Full narrative available

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