What happened
On May 12, 2011, at 20:36 hours, an MD-90 (registration B-17917), operated by Uni Airways Corporation, veered off the runway during its landing at Taoyuan International Airport. The flight, BR 806, originated from Macau Airport and was carrying 127 passengers and 7 crew members.
As the aircraft approached Runway 06, the flight crew encountered thunderstorms and heavy rain. During the landing roll, the right main gear veered off the runway at approximately 3,340 feet from the threshold. The aircraft drifted off the runway side before returning to the pavement at 5,100 feet. While the aircraft sustained minor damage to the landing gear flaps, engine exterior, and landing lights, there were no injuries to the passengers or crew.
The investigation
The investigation conducted by the TTSB utilized the Cockpit Voice Recorder (CVR), Flight Data Recorder (FDR), and interviews with personnel. Investigators examined the weather conditions, including a significant increase in left-side crosswinds and heavy rainfall that had accumulated on the runway.
Data from the FDR revealed that the left and right spoilers were not extended during the landing roll. The investigation also looked into the air traffic control (ATC) environment, noting high workloads and the failure to communicate recent changes in ground wind conditions to the flight crew. Additionally, the investigation reviewed the aircraft's descent profile and the crew's adherence to standard operating procedures (SOPs).
Findings
- The primary cause of the excursion was the failure to promptly extend the ground spoilers, which prevented the minimization of wing lift and failed to stabilize the aircraft against the wind.
- A significant increase in left-side crosswind (up to 18 knots) occurred during the landing roll, causing the aircraft to lean to the right.
- The flight crew did not use the thrust reversers effectively to reduce lateral pitch and counteract the weathercock effect.
- The flight crew was unaware of the dramatic change in wind speed prior to touchdown.
- The aircraft landed in an abnormal manner, with the nose gear and both main gears touching down simultaneously, which deviated from the MD-90 standard operating manual.
- The captain did not immediately take control of the aircraft when the landing became unstable.
- ATC failed to provide the most current wind information due to high workload and the prioritization of thunderstorm warnings.
- The aircraft's speed brake was not set to the ready position, which likely prevented the automatic extension of the spoilers.