What happened
On 10 March 2008, an Adam Air Boeing 737-400, registration PK-KKT, was operating a scheduled passenger flight from Jakarta to Batam with 177 people on board. During the approach to Hang Nadim International Airport, the flight crew initially attempted a landing but elected to perform a go-around because the approach was not stable. After being cleared to land again following improved visibility, the aircraft touched down on runway 04.
Upon touchdown, the crew noted the main wheels barely contacted the runway. As the aircraft decelerated below 30 knots, it began to yaw heavily to the right. Despite the crew applying full left rudder to correct the direction, the aircraft veered off the runway centerline and came to a stop on the shoulder, approximately 40 meters from the edge of the runway. There were no injuries among the 177 occupants, but the aircraft sustained serious damage, including a collapsed right main landing gear, a displaced engine, and damage to the right wing and flaps.
The investigation
The KNKT analyzed data from the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR). The CVR revealed that the aircraft had been flying below the correct glide path, triggering an aural warning, and recorded the landing gear warning following the collapse.
FDR analysis showed a vertical acceleration of 2.97g during the landing. While this impact level was not high enough to cause such structural failure under normal conditions, the investigation identified that the aircraft had experienced a hard landing and a bounce during a previous flight. Furthermore, physical examination of the failed right main landing gear strut revealed corrosion on the fracture surface.
Findings
- The approach was unstable, as the aircraft was flying below the established glide path.
- The right main landing gear collapsed due to a combination of a hard landing and pre-existing structural weakness.
- Corrosion on the fracture surface of the landing gear strut indicated a crack had likely been present for some time, compromising the component's strength.
- The operator failed to identify the degradation of the landing gear, potentially due to a lack of reporting regarding previous hard landings or deficiencies in the maintenance recording system.
Safety action
- The investigation highlighted the necessity of strictly adhering to stabilized approach criteria, specifically the requirement to execute a go-around if criteria are not met.
- The report emphasizes the importance of identifying and reporting all aircraft system failures and hard landing events to ensure proper maintenance intervention.