ATR72 N494AE incident near Dallas, Texas

Probable cause

A fatigue failure of an elevator stop bracket, which resulted in a partial jam of the elevator control. Contributing to the failure was the improper installation of shim stacks, poor alignment of the brackets, and cyclic stresses acting on the lower stop, generated by the repeated improper use of the gust lock system.

NTSB analysis

The flight crew reported that, while in level flight, they discovered that both control columns were jammed and they could only move the control column fore and aft a maximum of about 1 inch. After running checklist procedures without success, the flight crew slowed the airplane to 180 knots and were able to regain full control of the elevator. On final approach and after configuring for landing, the elevators again seemed to be jammed. The flight crew conducted a go-around and declared an emergency. During the second approach, with both control columns partially jammed, the flight crew performed a shallow approach to a smooth landing. A postincident examination revealed that brackets holding an elevator stop had fractured, causing the elevator movement to partially jam. The fractures were consistent with fatigue failure and were caused by a combination of improperly installed shim stacks, poor alignment of the L-brackets, and cyclic stresses acting on the lower stop, which were generated by the repeated improper use of the gust lock system.

Text from the NTSB. Open the NTSB docket for CEN10IA084 for the full record.