On May 8, 2003, a Canadair CL-600-2B19 (registration N829AS) operated by Atlantic Southeast Airlines, Inc. was involved in an aviation accident near Chattanooga, TN. Investigators recorded the probable cause as: Excessive wear on the bushings and the right aileron inboard and outboard power control unit output link resulting in the upward movement of the right aileron during cruise climb, uncommanded right roll. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.
Following takeoff, a flight crew encountered high-frequency vibration and an uncommanded roll. An emergency was declared. Post-flight inspection revealed worn aileron control components beyond maintenance limits.
Event Description
After departure, the flight crew detected a high-frequency vibration that was perceptible through the rudder pedals and control column. The Engine Indicating and Alerting System (EICAS) did not display any messages. The vibration, described as slow and increasing in intensity, persisted for approximately 30 seconds. The aircraft was cleared to 17,000 feet when it initiated an uncommanded roll to the right. The first officer disconnected the autopilot and successfully regained control. The captain subsequently declared an emergency and was cleared to divert to an alternate airport. During the descent and landing, the vibrations continued at all airspeeds.
Examination Findings
A subsequent inspection of the aircraft revealed that bushings and the right aileron inboard and outboard power control unit output link were worn. These components exceeded the authorized tolerances specified in the maintenance manual.
Manufacturer's Procedures
The manufacturer's inspection procedures for the aileron system backlash check did not require the operator to record the tolerance values found during the check.