Beech A36 N9087S accident near Amarillo, Texas

Probable cause

The loss of engine power due to a leak in the fuel control assembly. Contributing to the accident was the inadequate maintenance of the fuel control assembly.

NTSB analysis

The pilot stated that during a nonprecision instrument approach to the destination airport, he applied full engine power when he noticed that the airplane airspeed was decreasing. He realized that the engine lost power and was unsuccessful in attempts at regaining engine power. He performed a forced landing on a pasture during which the airplane sustained substantial damage that included damage to the right wing.

A postaccident examination of the wreckage revealed streaks fuel on the left side of the engine cowling. An examination of the engine revealed the fuel control assembly was leaking at the mixture control shaft’s O-ring. The O-ring was intact and did not exhibit separation. However, the outside diameter of the O-ring was less than the diameter of the mixture control shaft consistent with wear. A leak within the fuel control assembly would have allowed air to enter/fuel to exit the assembly resulting in improper fuel metering and a loss of engine power. No other mechanical anomalies were noted with the airframe and engine that would have precluded normal operations.

Maintenance records showed that the last overhaul of the fuel control assembly was performed during an engine overhaul in 1996. There were no subsequent records or evidence that indicated the assembly was overhauled after 1996.

The engine manufacturer’s recommended time between overhaul (TBO) was 12 years. The engine manufacturer’s standard practice manual stated that engine accessories must be overhauled at the time of engine overhaul. The engine and fuel control assembly exceeded the engine manufacturer’s recommended TBO.

Text from the NTSB. Open the NTSB docket for CEN22LA233 for the full record.