Ryan NAVION N5327K accident near Hurt, Virginia

Probable cause

Incorrect installation of the oil temperature probe and an inadequate annual inspection that failed to detect leaking oil around the loose probe, which resulted in a catastrophic engine failure due to oil starvation.

NTSB analysis

During cruise flight, the private pilot felt the engine suddenly begin to vibrate. He then heard a loud bang; the engine vibration increased, smoke and oil emanated from the engine compartment, and the engine lost total power. The pilot was unable to glide the airplane to a nearby airport and performed a forced landing in a field, during which the airplane struck and rolled through a fence, which resulted in substantial damage to the right wing. Examination of the engine revealed that its crankcase was absent of oil, and there were holes in the crankcase near cylinder Nos. 2, 4, and 6. Subsequent teardown examination revealed that the internal engine components exhibited heat distress consistent with a lack of lubrication. Further examination revealed that the oil temperature probe port was safety wired but could be moved by hand and that the crush washer between the probe and the cooler was installed backwards. This evidence is likely indicative that the probe had not been properly installed, although it could not be determined when that may have occurred. Air pressure applied to the oil cooler showed a leak between the oil temperature probe and the cooler. Oil residue noted on the exterior of the cooler indicated that the oil leak had likely been present for some time and that it was likely where the engine's oil had leaked out, ultimately resulting in the engine failure due to oil starvation. Had the leak been noted and addressed, by correctly installing the oil temperature probe, during the airplane's most recent annual inspection, which was completed 11 days before the accident, it is likely that the engine would not have been starved of oil.

Text from the NTSB. Open the NTSB docket for ERA16LA333 for the full record.