Investigation Summary
The accident aircraft had been idle for five weeks prior to the flight with its pitot tubes uncovered, allowing mud daubers to build nests inside. During the initial takeoff attempt, the crew rejected the takeoff due to a lack of airspeed indication. Instead of following the prescribed maintenance procedure of disconnecting the instruments and using compressed air, a mechanic used a screwdriver and a coat hanger to clear the obstructions, citing pressure from impatient passengers. Although a high-speed taxi test suggested the fix was successful, the NTSB noted that residual debris could have further compromised instrument reliability during the flight. Additionally, the flight was operated under Part 91 regulations to bypass the captain's expired Part 135 instrument check, a move the NTSB criticized as a lack of operational control.
Final Conclusions
The NTSB was unable to determine the probable cause of the accident due to the lack of physical evidence and flight recorders. However, the board identified three major contributing factors: flight into known thunderstorm activities and turbulence, pre-existing discrepancies in the pitot-static system affecting instrument reliability, and a lack of operational control by airline management.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Pitot-Static System
The system used to measure airspeed and altitude; it was obstructed by mud dauber nests prior to the flight.
Weather Radar
The aircraft was not equipped with radar, leaving the crew unaware of the severity of the thunderstorms ahead.
Interesting Facts
- 01The aircraft was 38 years old at the time of the accident.
- 02The pitot tubes had been left uncovered for five weeks, allowing mud dauber wasps to nest inside.
- 03The airline operated the flight under Part 91 rules because the captain was overdue for a 6-month instrument check required for Part 135 operations.
- 04The wreckage was never recovered as it was estimated to be at a depth of 1,800 feet.
- 05No flight data recorder or cockpit voice recorder was installed, as they were not required for this aircraft type at the time.
- 06Only 16 bodies were recovered before the search was terminated on September 15, 1980.
Safety Actions & Advisories
Maintenance Procedure Adherence
The NTSB emphasized the danger of using unapproved tools (like coat hangers) to clear pitot tubes and the necessity of following manufacturer-prescribed methods regardless of passenger pressure.
Known Controversies & Unanswered Questions
Sabotage Allegations
Reference ↗During the investigation, the NTSB received specific allegations regarding the possibility of sabotage or foul play. The FBI investigated these claims but ultimately discounted them, and the NTSB did not consider sabotage as a factor in its final evaluation.