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Atlas / NTSB / WPR23LA215

NTSB CAROL · Event

Event WPR23LA215

2023-06-04 Belfair, Washington, United States Airport · PWT Serious 1 aircraft Status: Completed

Aircraft involved

Probable cause & findings

The total loss of engine power due to the fatigue failure of the crankshaft accessory drive gear.

Factual narrative

On June 4, 2023, at 1130 Pacific daylight time, a Piper J-3C-65, N77583, was substantially damaged when it was involved in an accident near Belfair, Washington. The flight instructor and the student pilot were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor stated that he and the student pilot had been practicing maneuvers before they proceeded toward the Bremerton National Airport (PWT), Bremerton, Washington. The student pilot performed the before-landing checklist, which included checking fuel and turning on carburetor heat, as they were about 2 miles from runway 02. Shortly after, they heard a loud noise followed by a total loss of engine power. The flight instructor took control of the airplane and initiated a forced landing to an open area. During the landing roll, the airplane impacted rough and rising terrain. The left wing partially separated, and landing gear collapsed, which resulted in substantial damage to the fuselage. A postaccident examination of the airframe and engine revealed that, when the propeller was rotated, neither magneto coupling could be heard firing. The right magneto was removed, and remnants of the crankshaft accessory drive gear were observed in the accessory case. No additional, non-impact related anomalies were noted with the engine or airframe. The engine was disassembled, and the crankshaft and the gear remnants were removed and sent to the National Transportation Safety Board Materials Laboratory for further examination. The fracture faces of the gear contained mechanical damage. Two of the fracture faces contained fatigue striations typical of fatigue cracking that emanated from the root of the gear. The fatigue crack in these two gear fragments extended through the entire width of the gear. The terminus of each fatigue crack was not defined because of the severe mechanical damage on the fracture faces. The engine had accumulated about 278 hours since last overhaul and about 20 hours since the last annual inspection. The total number of hours on the engine could not be determined. The flight instructor reported that during an instructional flight, while approaching the airport to land, there was a loud noise followed by a total loss of engine power. The flight instructor took control of the airplane and initiated a forced landing to an open area. During the landing roll, the airplane impacted rough and rising terrain. The left wing was partially separated, and landing gear was collapsed. Postaccident examination of the engine found the crankshaft accessory drive gear had failed. Metallurgical examination of the crankshaft and gear remnants revealed the fracture surfaces of two of the gear teeth had signatures of fatigue. Mechanical damage to the terminus of the observed fatigue cracks prevented determination of the initiating event that resulted in the eventual failure of the gear. The failed gear prevented both magnetos from operating, which resulted in a total loss of engine power due to a lack of ignition. Source: NTSB Aviation Accident Database Retrieved: 2026-02-12

NTSB Findings

Hierarchical cause / factor breakdown from the FAA bulk avdata database. Each finding tagged C (Cause) or F (Factor).

  • Aircraft-Aircraft power plant-Accessory gear-boxes-(general)-Failure
  • Aircraft-Aircraft power plant-Engine (reciprocating)-Recip eng rear section-Failure
  • Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Altitude-Attain/maintain not possible

Verbatim from NTSB's published report. Source file NTSB_2023_WPR23LA215.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.

Related research

What the literature says.

Academic papers and agency reports matching this event's aircraft type or causal vocabulary (icing). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.

Browse the full corpus — academia portal ↗