Piper PA-28-161 N8149R accident near Lindenhurst, New York

Probable cause

An in-flight fire due to a compromised oil pressure line fitting, which resulted in a collision with terrain during a subsequent emergency landing.

NTSB analysis

The airplane departed with two passengers on a local “discovery flight.” After completion of the 40-minute flight, while established on a 3-mile final approach for landing, the pilot announced there was smoke in the cockpit and he requested an immediate landing. The pilot subsequently broadcast a “Mayday” over the tower frequency. The tower controller reissued an earlier landing clearance and observed smoke emanating from the left side of the airplane as it descended rapidly from view.

Local doorbell camera and surveillance video captured the airplane in a wings-level attitude, with smooth continuous engine sound until contact with trees and terrain.

Examination of the wreckage identified copper tubing and brass fittings associated with the oil pressure indicating system. These copper oil lines and fittings were on the cockpit side of the firewall and slightly offset toward the left side. The oil pressure tubing exhibited a branch line that was not part of the original design. It is not known exactly where this line was routed behind the instrument panel. At the end of this branch line a brass fitting exhibited melting consistent with very localized heating caused by electrical arcing. The appearance was that of sustained or repeated arcing as it melted through the fitting across multiple flats. The post-crash fire resulted in widespread, diffuse thermal exposure of the wreckage and aircraft components as exhibited by the melted regions of the fitting. If the fitting had reached its melting point due to the postcrash fire, it would have melted entirely without the localized melted region and sharp demarcation shown between melted and intact material.

Two previous reported incidents of smoke in the cockpit of the accident airplane occurred about 2 months and about 50 hours before the accident; however, the investigation could not conclusively determine if those events were related to the event during the accident flight.

It is likely that an intermittent electrical short circuit took place involving the fitting on the end of the oil pressure indicating line. Repeated electrical arcing eventually compromised the fitting enough to allow oil leakage and eventual ignition of the leaking oil, which resulted in an in-flight fire.

Text from the NTSB. Open the NTSB docket for ERA23FA137 for the full record.