Beech A36 N17544 accident near Austin, Texas

Probable cause

A total loss of engine power due to an excessively rich fuel mixture as a result of the improper adjustment of the fuel pump aneroid.

NTSB analysis

During a maintenance test flight, the airplane's fuel flow was slightly below normal, about 25-26 gallons per hour (gph) when it was normally 30-31 gph. The pilot selected the boost pump to "HIGH" and the fuel flow increased to 30 gph. A few seconds later, the fuel flow dropped to about 3 gph, and the engine stopped producing power. The pilot switched the boost pump off and on; however, the fuel flow did not chang. When the throttle was reduced, the engine momentarily surged. Engine power could not be restored, and the pilot performed a forced landing to a field.

An engine run was conducted after the accident, during which the engine again experienced a loss of power. The engine's fuel pump was removed and flow tested according to the supplemental type certificate holder's specifications. At an engine setting of 2,700 rpm, the fuel pump's flow pressure was 59.2 pounds per square inch (psi), above the maximum of 31 psi. The fuel pump's aneroid was found to be set incorrectly and was adjusted. During the subsequent flow test, the pump produced 31.3 gph. (The recommended maximum fuel flow for the fuel pump is 32 gph.) Review of maintenance logs revealed that the fuel pump was overhauled about 5 flight hours before the accident flight. It is likely that the aneroid was improperly set during this overhaul, which resulted in excessive fuel flow pressure.

The fuel pump was not the fuel pump recommended by the manufacturer; however, that did not play a role in the accident.

Text from the NTSB. Open the NTSB docket for CEN15LA336 for the full record.