What happened
On 19 October 2012, a Boeing 737-40 and registration PK-CKN, operated by PT. Sriwijaya Air, was performing a scheduled passenger flight from Jakarta to Pontianak. The flight, carrying 166 individuals, encountered heavy rain and thunderstorms during its approach to Supadio International Airport.
During the final stages of the approach, the aircraft's speed was recorded at 150 knots at 50 feet, which was 13 knots above the target Vref. As the aircraft touched down, it experienced a two-second bounce. During the landing roll, the aircraft encountered hydroplaning, significantly reducing braking effectiveness. The aircraft eventually came to a halt approximately two meters from the end of the runway stopway, with the nose wheels sinking into the soft ground.
The investigation
The KNKT investigation focused on landing distance calculations, approach preparation, and the occurrence of hydroplaning. Investigators examined flight data recorder (FDR) logs, which showed that while the pilot applied maximum braking, longitudinal deceleration decreased from -0.3 G to -0.1 G.
Physical evidence, including reverted rubber marks on the inner main wheels and white tire marks on the runway, confirmed that hydroplaning had occurred. Furthermore, a follow-up inspection of the runway during rain revealed standing water up to 15 cm deep at the intersection of the runway and taxiway Charlie. The investigation also reviewed the crew's approach briefing and landing performance calculations.
Findings
- The aircraft was airworthy and the crew held valid licenses.
- The approach was un-stabilized due to the speed being 13 knots above Vref at 50 feet.
- A 10-knot tailwind and a two-second bounce contributed to a required stopping distance of 7,515 feet, exceeding the available 7,382 feet.
- The crew failed to perform a complete approach briefing, specifically neglecting to review the required landing distance relative to the available runway length.
- Significant standing water on the runway surface facilitated hydroplaning.
Safety action
Following the incident, PT. Sriwijaya Air issued internal communications to remind pilots regarding adverse weather operations. The Supadio Airport Authority initiated plans to improve the runway drainage system and perform runway resurfacing. The KNKT issued recommendations to the airline to ensure consistent SOP implementation and to the airport authority to manage standing water levels during heavy rain.