What happened
On 6 February 2018, during the Singapore Airshow, a T-50 Golden Eagle operated by the Republic of Korea Air Force (ROKAF) experienced a runway excursion while performing a formation take-off from Changi Airport. As the aircraft accelerated down Runway 20R, it began to veer toward the right edge of the runway.
In an attempt to regain control, the pilot reduced engine thrust, deployed speed brakes, and applied full left rudder. The pilot then re-engaged the nose wheel steering (NWS) and applied full engine thrust to continue the take-off. This sequence caused the aircraft to zigzag across the runway for approximately 750 metres. The aircraft eventually drifted off the left edge of the runway, flipped over, and came to rest on the grass. A fire broke out in the tail section, which was quickly extinguished by airport rescue services. The pilot was the sole occupant and escaped the wreckage without injury.
The investigation
The investigation, conducted by the TSIB with support from the ROKAF Safety Investigation Board, examined flight data, cockpit video, and aircraft components. Investigators found that the aircraft's nose wheel was not perfectly aligned with the aircraft's nose at the moment the NWS was disengaged.
Technical inspections of the aircraft revealed no mechanical malfunctions in the cockpit or the NWS system. While the aircraft was destroyed, investigators noted that the tyres were within acceptable pressure ranges and showed wear consistent with the skidding motion. The investigation also reviewed meteorological data, noting a 10-knot tailwind was present during the departure.
Findings
- The initial rightward veer was caused by the disengagement of the nose wheel steering while the nose wheel was unaligned (at an angle of 1.31° to the right) and at a relatively low airspeed of 51.4 knots.
- Because of the tailwind, the aircraft's actual airspeed was lower than the pilot's estimated speed, meaning there was insufficient aerodynamic force on the rudder to correct the direction.
- The pilot's decision to re-engage the NWS while applying full left rudder caused the aircraft to swing abruptly to the left, leading to the uncontrollable zigzag motion.
- The pilot attempted to continue the take-off rather than aborting the maneuver, driven by a fixation on completing the scheduled aerial display.
Safety action
Following the incident, the ROKAF implemented several safety measures, including:
- Reminding pilots to strictly adhere to standard operating procedures regarding abnormal situations.
- Conducting simulator training sessions that replicate loss of directional control to reinforce the necessity of aborting take-offs when safety is compromised.