What happened
On April 19, 2018, a Malindo Airways Boeing 737-900, registration 9M-LNJ, was preparing for departure from Kathmandu's Tribhuvan International Airport to Kuala Lumpur. The weather conditions were characterized by drizzling rain and calm winds. During the takeoff roll, an audible and visual 'Take-Off Configuration' warning activated.
As the aircraft reached approximately 154 knots—a speed already past the decision speed (V1)—the captain elected to reject the takeoff. The pilot's decision was influenced by the surrounding high terrain and the deteriorating weather. Despite the crew applying braking pressure, the aircraft could not stop within the available runway distance, eventually skidding off the pavement and coming to rest approximately 50 meters beyond the runway threshold on soft ground.
Because the aircraft's position and the soft terrain prevented the use of mobile stairs, passengers and crew were evacuated via the 2R emergency slide. There were no injuries among the 132 passengers and 7 crew members.
The investigation
AAIB Malaysia examined the flight data, cockpit voice recordings, and maintenance records. The investigation focused on the sequence of braking and the validity of the configuration warning. Investigators found that while the first officer had checked the speed brake position, the warning persisted. Maintenance troubleshooting later revealed that the speed brake lever switch was providing an intermittent signal due to being out of range, rather than the handle being improperly stowed.
Furthermore, the investigation looked into the crew's procedures, noting that the autobrake system was disconnected immediately after the rejected takeoff was initiated, and maximum braking pressure was not applied consistently throughout the deceleration process. The investigation also noted that the captain had not conducted a pre-flight briefing with the cabin crew prior to the flight.
Findings
- The primary cause of the excursion was the pilot's attempt to reject the takeoff at a speed exceeding V1.
- The aircraft failed to stop because maximum braking pressure was not maintained throughout the entire deceleration period.
- The takeoff configuration warning was triggered by a faulty speed brake lever switch providing intermittent signals.
- The airline's standard operating procedures (SOP) for takeoff briefings did not clearly align with Boeing's Quick Reference Handbook (QRH) regarding specific RTO criteria for speeds above or below 80 knots.
- There was a lack of communication between the flight crew and cabin crew regarding the pre-flight briefing.
- The flight crew failed to preserve the flight recorders by not pulling the circuit breakers after the incident.