What happened
On 30 October 2009, a Boeing 737-30 and operated by Garuda Indonesia as flight GA142 was performing a scheduled service from Jakarta to Banda Aceh via Medan. The aircraft, registered PK-GGQ, was carrying 55 people, including 49 passengers and 6 crew members.
During the takeoff roll from runway 07L at Soekarno-Hatta Airport, the number-two main wheel separated from its axle and rolled onto the runway, striking and destroying a runway light. Air traffic controllers alerted the flight crew that a wheel had fallen off. The pilot in command elected to return to Jakarta, leveling off at 10,000 feet. After a 90-minute period of holding to manage fuel levels, the aircraft landed safely. No injuries were reported among the passengers or crew, though the aircraft required inspection and the detached wheel was recovered from the runway shoulder.
The investigation
An investigation by the KNKT focused on the mechanical failure of the landing gear assembly. Laboratory analysis of the failed components revealed that the inner race of the inboard bearing showed clear signs of true Brinelling. This condition is characterized by indentation marks on the bearing raceway caused by improper mounting.
Investigators traced the maintenance history back to 23 October 2009, when the wheel assembly had been removed to replace a brake unit. This maintenance task was performed on the airport apron during the night shift using flashlights for illumination. The investigation established that the work environment was not conducive to safe or precise maintenance procedures.
Findings
- The primary cause of the wheel detachment was the catastrophic failure of the wheel bearings.
- The bearing failure was triggered by an under-torque condition during the re-installation of the number-two main wheel following a brake replacement.
- The maintenance was conducted in a poor environment, specifically during hours of darkness using flashlights, which hindered the ability to follow approved procedures accurately.
- The physical evidence of Brinelling on the bearing races confirmed that the axle nut was not tightened to the required specification, leading to excessive loads and misalignment of the rollers.
Safety action
Following the incident, PT. GMF AeroAsia initiated several safety measures, including a quality assurance reminder for engineers and a scheduled retraining program focused on wheel and brake replacement. The Directorate General of Civil Aviation also directed Garuda Indonesia to re-torque the main and nose wheels on all its Boeing 737 aircraft at the first available opportunity and to implement more rigorous checklists for wheel installation.