What happened
On 9 March 1969, an aircraft was being moved into a hangar for a scheduled Check III inspection when the port elevator sustained damage after hitting passenger stairs. This necessitated an elevator replacement during the maintenance period. Following the repair, the pilot-in-command conducted a test flight at 0600 hours on 18 March 1969. During this flight, it was noted that the elevator trim was not functioning effectively. A subsequent inspection found that the elevator trim tabs had been incorrectly rigged in opposite directions.
The aircraft was returned to the hangar for corrections. A second test flight was attempted at 0600 hours on 19 March 1969. After performing ground runs and preflight inspections, the plane was sent back to the hangar because the elevator trim was reported as being very stiff. Following further work performed by an engineer and the pilot-in-command, a functional check of the trim mechanism was observed.
At 0730 hours on 19 March, the aircraft lined up for takeoff. Witnesses noted that the initial takeoff and climb phase appeared normal. Approximately two minutes into the flight, at an altitude of roughly 700 feet, the aircraft began a port turn at 160 degrees with a bank angle of about 300 degrees. Following this maneuver, the aircraft recovered from the turn only to enter an immediate and increasingly steep dive. The aircraft impacted the ground and caught fire, resulting in four fatalities among the crew.
Findings
The investigation determined that the elevator trim tabs had been installed in opposition, with one tab positioned up and the other down. This incorrect assembly of the elevator trim tab mechanism caused the sudden, uncontrollable dive.