Piper PA32 N31407 accident near Caro, Michigan

Probable cause

A total loss of engine power due to maintenance personnel’s failure to properly tighten the fuel supply line B-nut at the fuel servo.

NTSB analysis

The airplane had been in maintenance for 2 years before the accident flight, during which the engine crankcase was repaired and a new fuel servo was installed. After the work was completed, the mechanic asked the pilot to fly the airplane for 5 hours in the local area, after which he would inspect the engine again. Before the flight, the pilot performed a preflight inspection and added fuel to the tip tanks and the right main fuel tank.

He taxied to the runway and performed a run-up inspection, during which he noted an excessive drop in rpm on one of the magnetos. He added power, leaned the fuel mixture and ran the engine for about 2 minutes. A second magneto check indicated no anomalies. After takeoff, the pilot continued in the traffic pattern and, as he reduced the throttle on the downwind leg, the fuel flow decreased from 18 gallons per hour (gph) to about 15 gph. On final approach he increased the throttle and the engine did not respond. He then applied full power with no response from the engine and subsequently pitched the airplane for the best glide speed (87 knots).

The airplane cleared the trees at the end of the runway and impacted the grass about 200 yards short of the runway. As it touched down, the left main landing gear separated, and the airplane veered left and came to rest in a ditch. The airplane sustained substantial damage to the right horizontal stabilizer and both wings.

A postaccident examination of the engine revealed that, when the electric fuel pump was turned on, no fuel flowed from the injectors and a fuel leak was observed at the fuel servo. Further examination revealed the B-nut on the line from the fuel servo to the flow divider was loose at the fuel servo fitting. After the B-nut was tightened (between 1 and 1.5 turns), no leak was observed and fuel flowed evenly from all six injector nozzles.

Several other engine connections were found only finger tight, including the No. 1 upper spark plug, the No. 3 lower spark plug, and the No. 4 fuel injector nozzle. A compression check revealed air leakage from cylinder Nos. 1, 4, 5, and 6.

Based on the examination findings, the total loss of engine power likely resulted from the loose B-nut on the fuel line connection at the fuel servo, which allowed fuel to leak and prevented fuel from reaching the injector nozzles. Because the accident flight was the first flight following the maintenance and the fuel servo had recently been replaced, it is also likely that maintenance personnel did not adequately tighten the B-nut during maintenance.

Text from the NTSB. Open the NTSB docket for CEN24LA378 for the full record.