What happened
On 21 May 2014, a Singapore Airlines Airbus A330-300, registration 9V-STS, was performing a scheduled passenger flight from Singapore to Yangon, Myanmar. During the approach to Runway 21, the flight crew encountered shifting crosswinds and rain showers. As the aircraft descended below 100 feet, the pilot attempted to correct for a change in wind speed, but an over-correction caused the aircraft to drift toward the right side of the runway.
Despite a call for a go-around from the co-pilot, the pilot-in-command elected to proceed with the landing. The aircraft touched down approximately 26 metres from the runway centerline, very close to the edge. Shortly after touchdown, the right main landing gear exited the paved surface. The aircraft traveled roughly 600 metres off the pavement before the crew managed to steer it back onto the runway. There were no injuries among the 265 people on board.
The investigation
The investigation examined the flight data, cockpit voice recordings, and the physical state of the airfield. Investigators analyzed the flight crew's manual handling of the aircraft, noting that the pilot had disconnected the autopilot at 1,100 feet. The study also looked into the mechanical consequences of the excursion, specifically the damage to the aircraft's green hydraulic system, which resulted in the loss of nose wheel steering capability. Additionally, the condition of the runway shoulder was evaluated to determine if the uneven surface contributed to the aircraft's movement off the pavement.
Findings
- The primary cause of the excursion was the pilot's over-correction during the final approach, which induced a rightward drift.
- Conflicting control inputs were recorded; the co-pilot applied left roll input while the pilot-in-command applied right roll input, resulting in a net rightward roll that maintained the drift.
- The approach was considered unstabilized due to the aircraft's deviation from the centerline.
- The runway shoulder was not flush with the runway surface and was uneven, failing to meet international safety standards.
- The aircraft sustained damage to its hydraulic system, flap fairings, and tires, and the left engine ingested mud and debris.
Safety action
Following the incident, the aircraft operator implemented several training updates, including exercises for landing in gusty crosswinds and training on proper side-stick handling to prevent inadvertent roll inputs. There was also a safety recommendation for the aerodrome operator to improve the runway shoulder to ensure it meets ICAO requirements.