Beech F33A N84MD accident near Puyallup, Washington

Probable cause

A total loss of engine power due to fuel starvation as a result of a mechanic’s failure to properly tighten the B-nut to the fuel pump inlet during a recent annual inspection. Contributing to the accident was the pilot's decision to take off despite indications that the engine was not operating normally.

NTSB analysis

The private pilot was conducting the airplane's first flight after an annual inspection. On the morning of the accident, the pilot picked up the airplane and conducted a run-up, during which the engine lost power. The airplane was towed back to the maintenance shop, and a mechanic recommended that the pilot wait until a more detailed examination could be completed. The pilot downloaded the data from the airplane's engine data monitor and took it home to examine. After returning to the airport later that day, the pilot reported to the mechanic that he did not observe anything abnormal in the data, and he got back in the airplane to depart for the accident flight. The pilot reported that, about 350 ft above the ground during initial climb, the engine lost power with no abnormal noises or sounds, and he landed in a field. The airplane subsequently rolled down an embankment, the nosewheel collapsed, and the airplane then came to rest.

During a postaccident engine run, the airplane started without hesitation; however, it lost power after the fuel boost pump was turned off. Further examination revealed that the B-nut to the fuel pump inlet was loose. The B-nut was tightened, and the engine then started and operated up to about 2,100 rpm with no additional anomalies. Data from the engine's data management system were analyzed, and the data revealed seven separate data sessions on the day of the accident, six leading up to the accident session. Based on the evidence, it is likely that the mechanic did not properly tighten the B-nut to the fuel pump inlet during the annual inspection and that the loose B-nut at the fuel pump resulted in the airplane being starved of fuel without the assistance of the pump. The accident likely would have been avoided if the pilot had not attempted to take off with indications that the airplane was not operating normally.

Text from the NTSB. Open the NTSB docket for WPR15LA167 for the full record.