Investigation Summary
The accident occurred just as Provincetown-Boston Airlines (PBA) was attempting to restore its reputation following a grounding by the FAA for safety violations in November 1984. Flight 1039 was climbing through approximately 600 feet when the crew acknowledged a frequency change. Seconds later, the aircraft entered a steep descent. Post-crash analysis revealed that the horizontal stabilizer, elevators, tail cone, and part of the ventral fin had separated before impact. The NTSB found that the left elevator control rod had failed due to overstress, leading to asymmetrical elevator movement. This created aerodynamic loads that exceeded the design limits of the horizontal stabilizer attachment structure, specifically at bulkhead No. 36. Because the aircraft was not equipped with a Cockpit Voice Recorder (CVR) or Flight Data Recorder (FDR), investigators could not determine the exact nature of the initial pitch control malfunction that triggered the pilots' fatal corrective inputs.
Final Conclusions
The NTSB concluded that the probable cause was a malfunction of either the elevator control system or elevator trim system, resulting in a pitch control problem. The flight crew's reaction to this problem overstressed the left elevator control rod, causing asymmetrical elevator deflection and the subsequent overstress failure of the horizontal stabilizer attachment structure. The precise initial malfunction remained undetermined due to the lack of flight recorders.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Thomas Ashby, age 34. Hired by PBA in 1974.
First Officer
Louis Fernandez, age 25. Hired by PBA in 1984.
Systems & Failure Modes
Elevator Control System
The system responsible for controlling the aircraft's pitch; a failure in the left elevator control rod led to asymmetrical deflection and structural failure.
Horizontal Stabilizer Attachment
The structural assembly, including bulkhead No. 36, which failed under extreme aerodynamic loads caused by the elevator malfunction.
Elevator Trim System
A secondary system used to reduce control column pressure; investigators identified a potential runaway trim or malfunction as a trigger for the accident.
Interesting Facts
- 01The horizontal stabilizer landed 1,100 feet short of the primary crash site.
- 02The aircraft was operated within its designed gross weight and center of gravity limits.
- 03PBA had been grounded by the FAA on November 10, 1984, and had only resumed full service two days before the crash.
- 04The crash was non-survivable due to impact forces that collapsed the fuselage downward to the seat pans, reducing cockpit and cabin volume by 50 percent.
- 05The aircraft was not equipped with a CVR or FDR, as they were not yet required for multi-engine turboprop aircraft of this size.
- 06The aircraft's Manufacturer Serial Number (MSN) was 110365.
Safety Actions & Advisories
CVR/FDR Mandates
The NTSB used the accident to urge the FAA to expedite rules requiring Cockpit Voice Recorders and Flight Data Recorders on multi-engine, turbine-powered passenger aircraft.
Runaway Trim Training
The NTSB recommended enhanced training for regional airline crews regarding runaway trim emergencies, including simulator demonstrations of the forces required to maintain control.
Known Controversies & Unanswered Questions
Confusion with PBA Flight 1033
Reference ↗Public accounts and some social media summaries occasionally conflate Flight 1039 with PBA Flight 1033, which occurred in September 1984. The 'burnt-out landing gear indicator' and 'bumped controls' theory belongs to the Flight 1033 investigation; for Flight 1039, the NTSB officially stated the precise initial malfunction could not be determined due to the lack of flight recorders.