What happened
On November 7, 2011, a Boeing 767-30/300 was performing a takeoff roll at Katowice Airport (EPKT). During the acceleration phase, the crew observed a yellow warning message on the upper EICAS indicating a LEFT YAW DAMPER malfunction. In response to this alert, the captain initiated an aborted takeoff at a speed of 47 knots. The decision to abort the takeoff did not pose a threat to the safety of the passengers or the crew.
Following the aborted takeoff, the captain notified the flight attendant and the tower controller. The aircraft taxied to taxiway D, where the crew contacted Maintenance Control Center (MCC) for assistance. Following instructions, the aircraft taxied to the gate, and the passengers were informed of the necessity to disembark. After a technical inspection, maintenance personnel cleared the aircraft for flight under the provisions of MEL 22-21-01. During the subsequent departure and the remainder of the flight, the warning did not recur.
The investigation
The investigation focused on the technical failure that triggered the EICAS warning. It was determined that the malfunction was localized to the yaw damper system. Maintenance records indicated that on November 12, 2011, the fault was rectified by replacing the Control Pressure Switch S29 in accordance with the Aircraft Maintenance Manual (AMM) 29-11-19. Following the replacement, successful functional tests were performed on both the left and right yaw damper systems.
Findings
- The primary cause of the incident was a malfunction of the Control Pressure Switch S29 within the yaw damper system.