Loss of Control in Flight · NTSB WPR20FA077
Stinson V77 — Auburn, CA
| Date | January 24, 2020 |
| Location | Auburn, CA |
| Aircraft | Stinson V77 |
| Purpose of flight | Personal |
| Conditions | Day · Visual Meteorological Cond |
| Phase / occurrence | Enroute Collision with terr/obj (non-CFIT) |
| Pilot age | 55 |
| Pilot total time | 650 hrs · Building experience |
| Time in type | Unknown |
| Fatalities | 2, 1 serious |
Probable cause
NTSB findings
- Aircraft-Aircraft power plant-Engine (reciprocating)-Recip eng cyl section-Failure
- Aircraft-Aircraft power plant-Engine (reciprocating)-Recip eng wiring-Damaged/degraded
- Aircraft-Aircraft power plant-Ignition system-Spark plugs/igniters-Damaged/degraded
- Environmental issues-Physical environment-Terrain-Mountainous/hilly terrain-Contributed to outcome
- Personnel issues-Task performance-Maintenance-Scheduled/routine maintenance-Maintenance personnel
What happened
The pilot departed on a local flight with two passengers. Several witnesses reported that they heard the airplane’s engine backfiring and sputtering and subsequently heard the engine quit. The surviving passenger, who was seated in the front right seat, stated that the engine lost power and there was nowhere to land. The airplane subsequently impacted heavily wooded terrain about 1 mile from the departure airport.
Postaccident examination of the engine revealed that the No. 7 cylinder intake valve was stuck open. The No. 2 cylinder front spark plug was defective, and the Nos. 2- and 4-cylinders’ ignition wires were frayed, worn, and displayed arcing, which likely led to erratic operation or a lack of ignition in these two cylinders. The culmination of these issues most likely led to the engine running rough, backfiring, and subsequently losing total power.
An annual inspection was accomplished on the airframe and engine about 2 months before the accident. General maintenance practices and the inspection should have identified the anomalies that were found during the postaccident engine examination.