Mooney M20E N1310W accident near Marked Tree, Arkansas

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 analysis

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.

Text from the NTSB. Open the NTSB docket for CEN12FA463 for the full record.