N151DC

On April 18, 2016, about 1530 Eastern daylight time, a Piper PA-28-161, N151DC, was substantially damaged when it was involved in an accident near Okeechobee, Florida. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 solo instructional flight.

The operator reported that, when the airplane was about 3,000 ft mean sea level, the engine suddenly started to run roughly accompanied by “abnormal” noises. The engine instruments remained in the normal range. The pilot attempted to troubleshoot the problem by performing the “engine roughness” checklist without success. Shortly after, the pilot contacted the Miami Air Route Traffic Control Center and reported the problem, and a controller suggested that the pilot proceed to the St Lucie County International Airport (FPR), Fort Pierce, Florida, where emergency services would be standing by. However, about 10 seconds after completing the checklist, the engine lost all power. The pilot then established the best glide speed and chose a private grass strip for forced landing and conducted the “engine power loss in flight” checklist without success. Once committed to landing, he conducted the “power off landing checklist.” After touching down, the airplane skidded and subsequently impacted farm equipment and other obstacles, and it then came to rest against a building.

A review of the engine’s maintenance records revealed that it had accrued 10,382.8 total flight hours and 2,600.8 hours since the last overhaul. The engine manufacturer’s recommended time between overhaul was 2,400 hours.

Postaccident examination of the airplane revealed that it had sustained substantial damage to the fuselage and tail section and that the wings had been sheared off. During postaccident examination of the engine, a hole was found in the crankcase above the No. 2 cylinder. Metal was found in most of the folds of the oil filter material and in the Nos. 3 and 4 cylinders, and ferrous and nonferrous materials were found throughout the crankcase.

During a subsequent compression check, the No. 3 cylinder’s compression was excessively low, The No. 3 piston would not move when the crankshaft was manually rotated. After the No. 3 cylinder was removed, only the connecting rod and piston pin were found. The No. 3 cylinder’s interior was extensively damaged.

Metallurgical examination of the No. 3 piston revealed that it was fractured and that it had two fatigue cracks emanating from the outer face of a lubricating hole in a groove for a compression ring. (See figure 1, which is a photograph showing the two fatigue cracks in the No. 3 piston in relation to the lubricating hose and compression ring groove. The white arrows indicate the general direction of the fatigue crack propagation.) The areas outside of the fatigue crack regions and fracture faces exhibited a rough texture and on-slant planes consistent with overstress separation. The reason for the initiation and propagation of the fatigue cracks could not be determined.

Figure 1. Photograph showing the No. 3 piston’s two fatigue cracks in relation to the lubricating hole and compression ring groove and the general direction of the fatigue propagation.