What happened
On 23 July 2008, a Boeing 73 and 400, registered PK-GZN, was operating a scheduled flight from Jakarta to Banjarmasin with 121 people on board. The flight crew reported a routine touchdown at Syamsudin Noor Airport. During the landing roll, as the aircraft slowed to approximately 60 knots, the pilot applied manual braking, which triggered an anti-skid malfunction light.
While taxiing toward the apron, the pilot noticed the aircraft pulling to the left and reduced speed. As the aircraft turned right into taxiway B, a loud noise, similar to a tire bursting, prompted the pilot to stop the aircraft. Upon inspection by ground engineers, it was discovered that the number-one main landing gear axle had broken and detached from its strut, which subsequently caused the number-two tire to burst. There were no injuries among the 114 passengers or 7 crew members.
The investigation
Investigators examined the wreckage and the failed component to determine the cause of the structural failure. Metallurgical analysis conducted by the Institute of Technology, Bandung, revealed that the failure was caused by a fatigue crack. The fracture surface exhibited beach marks, which are characteristic of progressive fatigue. The investigation established that the crack originated from a corroded hole within the brake assembly attachment flange and propagated inward toward the axle wall. The crack reached a length of approximately 6 cm before a sudden, catastrophic final fracture occurred.
Findings
- The primary cause of the failure was an undetected fatigue crack in the number-one main landing gear axle.
- The crack originated from a site of corrosion located at the edge of a brake mounting hole.
- The fatigue crack propagated through the axle wall until it reached a critical size, leading to the complete separation of the axle from the strut.
- The failure occurred well before the component reached its manufacturer-specified service life.