Cessna 172 N99442 accident near Palatka, Florida

Probable cause

The failure of the nose oil seal to remain secure in the engine crankcase, which resulted in a loss of engine oil and partial loss of engine power.

NTSB analysis

The pilot reported that when attempting to climb from his cruise altitude to an altitude at which he could begin a practice approach, the engine began to run rough and climb performance deteriorated. He discontinued the practice approach and turned direct to the airport; checking his instruments, he saw that the engine oil pressure was low and "in the red.” While proceeding to the airport, the engine performance continued to degrade, and the pilot was unable to maintain altitude. About 2 miles from the airport, the pilot realized he would not be able to make the runway and performed a forced landing in a field. The airplane sustained substantial damage to the fuselage during the landing.

Postaccident examination of the engine found the nose oil seal was protruding about 3/8 inch out of the recess in the crankcase, which allowed engine oil to be expelled from the crankcase and resulted in the loss of oil pressure. The crankshaft main journals and bearings and the rod journals and bearings exhibited light scoring. This was likely due to the lack of oil for lubrication and resulted in the power loss that the pilot experienced as the journals and bearings began to overheat. The engine had been operated for about 6,089 hours during the 19-year period since its last overhaul. The engine manufacturer recommended overhaul at 12 years or 2,000 hours of operation, whichever occurred first. Had the engine been overhauled in accordance with the engine manufacturer’s recommendations the nose oil seal would have been replaced, and it is likely that it would have remained secure.

Text from the NTSB. Open the NTSB docket for ERA24LA198 for the full record.