The private pilot, who was also the builder of the experimental, amateur-built Sonex, reported that, during initial climb for the local flight, about 3,000 feet mean sea level, the propeller separated from the airplane and fell to the ground.
He turned the airplane toward an airport in Morganton, N.C., that had a longer runway than the departure airport and attempted to glide the airplane to the runway. However, the plane did not have sufficient altitude, and it subsequently hit trees about 600 feet short of the runway.
Photographs of the crankshaft revealed that it fractured just aft of the propeller mounting hub/flange. The fracture surfaces on the hub exhibited features consistent with fatigue crack propagation through the wall thickness of the crankshaft and the subsequent overstress fracture of the remaining portion of the crankshaft.
Review of maintenance records revealed that the airplane had sustained a propeller strike about seven years before the accident. After that, the owner, who performed his own maintenance, replaced the propeller, however, he did not disassemble the engine or otherwise document any inspection or replacement of the crankshaft in the airplane’s maintenance records.
Probable cause: The pilot/owner’s inadequate maintenance inspection following a propeller strike, which resulted in the subsequent in-flight propeller separation due to propagation of fatigue cracks in the crankshaft.
NTSB Identification: ERA16LA041
This November 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Shoulda woulda coulda. In hindsight better choice shoulda been runway just departed. If you can takeoff from runway you can obviously land on it and with the AGL (unreported) reached shoulda (presumably) been able to make that runway as opposed to trying to stretch glide to another runway whose sole attraction was its greater length but that would have required pretakeoff planning which also requires review of glide ratio (distance vs. altitude) in quick and easy recall terms. The bigger shoulda was tearing down that engine rather than trusting the integrity of the crank shaft after having been exposed to a sudden stoppage prop strike. That’s blind trust which seldom turns out to be a good decision.
I went to the full report and the airport he took off from elevation is 1195′.
Good news: It was Darwin’s day off. Good news: Pilot enjoys maximum glide with no prop drag. Good news, Bad news, took easy out seven years before and didn’t tear down engine. Bad news, didn’t pick an intermediate field and instead fixated on landing at an airport. Bad news, wishful thinking is not a sign of good planning.
Good news – the Bad news = Lotsa Luck!