CEN24LA378

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.

On September 30, 2024, about 1230 eastern daylight time, a Piper PA-32-300 airplane, N31407, was substantially damaged when it was involved in an accident near Caro, Michigan. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. According to the pilot, the airplane had undergone maintenance over the previous two years, during which the engine was overhauled. Upon completion of the maintenance, the mechanic asked the pilot to fly the airplane for 5 hours in the local area; he would then remove the cowling and reinspect the engine. On the day of the accident, the pilot performed an extensive preflight inspection and added fuel to the tip tanks and the right main fuel tank. He taxied to the end of the runway and performed a run-up inspection. According to the pilot, one of the magnetos had an “overly extensive drop in RPMs.” He added power, leaned the fuel mixture, and ran the engine for about 2 minutes. The pilot then performed another magneto check that indicated no anomalies. He turned the fuel pump on, selected the right main fuel tank, and taxied onto the runway. The takeoff was normal, and the pilot continued on the crosswind and downwind legs of the traffic pattern. As the pilot reduced the throttle on the downwind leg, he noticed the fuel flow decreased from 18 gph to about 15 gph. He continued onto the base leg and then, on final approach, he increased the throttle and the engine did not respond. The pilot applied full power with no response from the engine and then pitched the airplane for the best glide speed (87 knots). The airplane cleared the trees at the end of the runway and then remained “just above stall” until it impacted the grass about 200 yards short of the runway. The left main landing gear separated, and the airplane veered to the left coming to rest in a ditch. The airplane sustained substantial damage to the right horizontal stabilizer and both wings. A postaccident examination of the airplane revealed the presence of fuel in both main fuel tanks and the left auxiliary tank; it was blue in color and had an odor similar to 100LL aviation fuel. The right auxiliary tank ruptured during the accident sequence. Fuel was drained from the fuel strainer, and a small amount of black contamination was observed. Examination of the engine revealed that the No. 1 upper spark plug and the No. 3 lower spark plug were finger tight. Additionally, the No. 4 fuel injector nozzle was finger tight in the cylinder. When the electric fuel pump was turned on, no fuel flowed from the injectors and a fuel leak was observed at the fuel servo. The fuel pump was shut off and the B-nut on the line from the fuel servo to the flow divider was found to be loose at the fuel servo fitting. The B-nut was tightened (between 1 and 1.5 turns), and the fuel pump was turned back on. No leak was observed and fuel flowed evenly from all six injector nozzles. A compression check was performed on the engine.As the propeller was rotated by hand, air leakage was noted on cylinder Nos. 1, 4, 5, and 6. All six cylinders were inspected with a borescope; all showed crackling in chrome plating. The valve seats on cylinder Nos. 1, 4, 5, and 6 showed evidence consistent with leakage. A dipstick check of the oil confirmed 10 quarts of oil in the engine; a sample was drained from the sump drain valve with no contaminants observed. The oil filter was removed and cut open; contaminants were observed in the filter pleats. A review of the engine logbook revealed an annual inspection was completed five days before the accident after completion of the repairs. The entry for the inspection specified that the engine crankcase was repaired due to a bearing failure corresponding to the statement from the pilot regarding the two years of maintenance. The entry further stated that new main bearings, a gasket set, and new ball bearings were installed; the fuel servo was also “exchanged” from the manufacturer. According to the entry, the engine was run on the ground for 15 minutes, checked for leaks, and run for another 15 minutes. No anomalies were noted in the logbook entry.