What happened
On 2 September 1999, a China Airlines Boeing 747SP, registration B-18253, was conducting a type check flight for two first officers at Chiang Kai-shek International Airport. Following landing on Runway 06, the pilot-in-command attempted to exit the runway by steering left toward Taxiway S5. At a speed of 76.8 knots, the aircraft failed to complete the turn and veered onto the adjacent grass strip.
During the excursion, the aircraft's nose gear and left body gear collided with a protruding concrete manhole located approximately 11 meters from the runway edge. The impact was severe, snapping the front and rear axles of the left body gear truck and causing the separation of the #5 and # and #6 wheels. The collision also damaged the aircraft's belly structure and caused the #1 engine to make contact with the ground. There were no fatalities or injuries reported during the incident.
The investigation
In coordination with the Civil Aeronautics Administration (CAA) and China Airlines, the investigation team analyzed data from the Flight Data Recorder and Cockpit Voice Recorder. Investigators also examined tire tracks on the runway, conducted tests on the nose gear steering system, and inspected the physical condition of the manhole. The investigation focused on the aircraft's deceleration, steering inputs, and the structural adequacy of the airport's runway strip infrastructure.
Findings
- The pilot-in-command failed to select an appropriate runway exit point prior to touchdown that accounted for the aircraft's braking characteristics.
- The pilot applied nose gear steering before reaching the necessary rolling speed, and reverse thrust and braking were not applied at the required speed.
- The aircraft's light weight and an aft center of gravity increased the tendency to pitch up, which caused the nose wheel to slip laterally despite steering inputs.
- The protruding manhole was an indirect cause of the damage; its location, design, and construction failed to meet both domestic and ICAO standards.
Safety action
- China Airlines was advised to ensure flight crews operate strictly according to flight manuals and to establish specific rolling speeds for various flight conditions in the Boeing 747SP Flight Manual.
- The CAA was recommended to inspect all fixed structures, such as manholes, around the runway strips at Chiang Kai-shek International Airport to ensure compliance with international safety standards and to assess runway strip transverse slopes.