Investigation Summary
The investigation revealed that the Lockheed Electra's Allison 501-D13 turboprop engines were uniquely vulnerable to bird ingestion. Engine one ingested at least eight starlings, triggering the autofeather system and shutting down the engine. Simultaneously, engines two and four ingested birds, causing substantial power losses. A critical design limitation of the Electra's autofeather system meant that only one propeller could autofeather at a time; this prevented the propellers on engines two and four from feathering, creating severe asymmetric thrust and drag. The situation was further complicated by bird remains clogging the pitot tubes, which likely provided the pilots with unreliable airspeed readings. While the bird strike was the primary cause, subsequent civil litigation highlighted a significant maintenance failure: the co-pilot's seat was known to be defective and prone to sliding backward. It was theorized that during the emergency, the co-pilot's seat may have slipped, causing an inadvertent pull on the yoke that exacerbated the stall. The flight was scheduled to continue to Charlotte and Greenville before terminating in Atlanta.
Final Conclusions
The Civil Aeronautics Board concluded the accident was caused by the ingestion of a large number of starlings into three engines, resulting in a loss of power and a subsequent stall at an altitude too low for recovery. The board also noted that the turboprop engines of the era lacked sufficient resilience against bird strikes.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Allison 501-D13 Turboprop
The engines were found to be highly sensitive to bird ingestion, which caused immediate power loss or thrust degradation.
Autofeather System
Designed to reduce drag in the event of engine failure, but limited by design to only allow one propeller to feather at a time when armed. This prevented engines 2 and 4 from feathering despite their power loss.
Pitot-Static System
Clogged by bird remains during the strike, leading to the loss of accurate airspeed data for the flight crew.
Interesting Facts
- 01Engine one ingested at least eight birds, while engines two and four ingested at least one each.
- 02Investigators recovered approximately 75 starling carcasses on or near the runway area where the encounter occurred.
- 03The entire flight from takeoff roll to impact lasted less than one minute.
- 04The fuselage broke into two pieces upon impact; the rear section remained buoyant long enough for ten survivors to be rescued.
- 05Bird remains were found in the pitot tubes, which would have rendered airspeed indicators unreliable.
- 06Maintenance records showed the co-pilot's seat was defective and had been repaired with wire instead of a proper metal rod.
Safety Actions & Advisories
Turbine Engine Resilience
The CAB recommended that the CAA take steps to improve the bird-strike resistance of turbine engines.
Airport Wildlife Management
Recommendations were made to implement methods to reduce bird populations in the immediate vicinity of airport runways.
Known Controversies & Unanswered Questions
Co-pilot Seat Failure
Reference ↗During civil litigation, it was argued that a known maintenance defect in the co-pilot's seat caused it to slide back during the emergency, leading to an inadvertent control input that induced the final stall.