Serious incident Bombardier CRJ-200ER N829AS, Thursday 8 May 2003

You can contribute by submitting additional or updated information.

Date:	Thursday 8 May 2003
Time:	12:28 LT
Type:	Bombardier CRJ-200ER
Owner/operator:	Atlantic Southeast Airlines - ASA
Registration:	N829AS
MSN:	7232
Year of manufacture:	1998
Total airframe hrs:	13127 hours
Engine model:	General Electric CF34-3BI
Fatalities:	Fatalities: 0 / Occupants: 21
Other fatalities:	0
Aircraft damage:	None
Category:	Serious incident
Location:	Chattanooga, TN - United States of America
Phase:	En route
Nature:	Unknown
Departure airport:	Atlanta Hartsfield-Jackson International Airport, GA (ATL/KATL)
Destination airport:	Montreal-Pierre Elliott Trudeau International Airport, QC (YUL/CYUL)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
After takeoff the flight crew heard a high frequency vibration which could be felt in the feet and control column. The engine indicating and alerting system indicated no messages. The vibration was slow and increased in intensity and lasted about 30 seconds. The flight was cleared to 17,000 feet, and the airplane started an uncommanded roll to the right. The first officer disconnected the autopilot and regained control of the airplane. The captain declared an emergency, and was issued a clearance to an alternate airport. The vibrations continued at all airspeeds during the descent and landing. Examination of the airplane revealed the bushings and right aileron inboard and outboard power control unit output link were worn and exceeded the authorized tolerance allowed by the maintenance manual. The aircraft manufacturers inspection procedures for the aileron system backlash check did not require the operator to record the tolerance found during the backlash check.

Probable Cause: 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. A factor in the accident was inadequate maintenance inspection procedure by the aircraft manufacture for the aileron system backlash check performed by the operator. The inspection procedure did not require the operator to record the tolerance found during the backlash check.

Accident investigation: