Investigation Summary
The accident occurred during the first flight following a Phase 1 and Phase 2 maintenance check, which included flight control cable rigging. During the maintenance, the elevator trim cables were crossed: the inboard cable at the Fuselage Station (FS) 798 floor beam was routed through the lower fairlead hole instead of the upper hole, reversing the system's logic. Post-maintenance inspections failed to detect this error; specifically, the Required Inspection Item (RII) inspector did not sign off on the elevator servo trim tab cable connection and rigging, despite a bold note on the maintenance card requiring an RII signature. During the takeoff roll, as the aircraft reached rotation speed, the reversed trim began applying nose-down force. The captain, unaware of the reversal, likely attempted to trim the nose up to relieve control pressure, which only exacerbated the nose-down condition. The Cockpit Voice Recorder (CVR) captured the captain shouting "pull" 27 times as the crew struggled against the controls. The aircraft reached approximately 900 feet above ground level before descending into a cornfield approximately one mile southwest of the runway. The investigation also noted that the crew failed to activate the Flight Data Recorder (FDR) and did not follow standard procedures for a post-maintenance flight, such as performing a thorough control check that might have revealed the reversed trim on the ground.
Final Conclusions
The NTSB determined the probable cause was the improper (reverse) rigging of the elevator trim cables by company maintenance personnel and the failure of the RII inspector to discover the error during post-maintenance checks. Contributing factors included the captain's inadequate post-maintenance preflight check and the flight crew's improper response to the trim problem, specifically their failure to stop making additional trim inputs and return the aircraft to its previous configuration before the condition worsened.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Total hours from BAAA source.
First Officer
Total hours from BAAA source.
Systems & Failure Modes
Elevator Trim System
A mechanical cable-and-pulley system that adjusts the pitch of the aircraft. In this case, the cables were cross-connected, reversing the direction of the trim tab relative to the cockpit wheel.
Flight Data Recorder (FDR)
The aircraft was equipped with an FDR that required a manual cockpit switch to be set to 'ON'. The crew failed to activate it, resulting in no data for the accident flight.
Interesting Facts
- 01The elevator trim cables were found to be reversed aft of Fuselage Station 798.
- 02The Required Inspection Item (RII) inspector failed to sign off on the elevator trim rigging task.
- 03The Flight Data Recorder (FDR) was not powered on during the flight because the crew skipped the checklist item.
- 04The captain repeated the word 'pull' 27 times during the 2-minute 40-second flight.
- 05The aircraft was a 1956-built Convair CV-580 converted for cargo operations.
Safety Actions & Advisories
Maintenance Inspection Oversight
The investigation highlighted the critical necessity of RII (Required Inspection Item) signatures, emphasizing that mechanics and inspectors must independently verify flight control rigging.
Location
ACCIDENT SITE · Coordinates taken from the wikidata coordinate.