What happened
On 18 July 2010, a De Havilland DHC6-300 Twin Otter, registration PK-NUH, was performing a scheduled flight from Bintuni Airport to Sorong, West Papua. The aircraft was carrying two crew members and seven passengers. During the takeoff roll on runway 31, the pilot monitoring called for rotation. Approximately one second later, the pilot monitoring observed the engine torque indicator drop to zero and alerted the flight crew of a failure.
In response, the pilot flying initiated an aborted takeoff by reducing power and engaging reverse thrust. During the deceleration, the aircraft veered to the right of the centerline. The heavy braking required to stop the aircraft resulted in both main landing gear tires becoming flat. The aircraft eventually came to a rest on the right shoulder at the end of the runway. While there were no injuries among the nine people on board, the aircraft sustained damage, including a collapsed nose landing gear and a bent right footstep.
The investigation
The investigation focused on the mechanical cause of the instrument failure and the execution of the aborted takeoff. Investigators discovered that a melted fuse had caused the engine torque indicator to drop to zero. Notably, a nearly identical issue involving a melted fuse had occurred on the same aircraft two weeks prior.
Analysis of the takeoff parameters revealed that the decision to abort the takeoff was made after the aircraft had already passed V1, the maximum decision speed. Furthermore, the investigation examined the crew's response and training, noting that the heavy braking applied during the abort led to the tire deflation and subsequent loss of directional control.
Findings
- The engine torque indicator failure was caused by a melted fuse.
- The decision to abort the takeoff was initiated after the aircraft had exceeded V1 speed.
- The aircraft veered off the runway because the right main landing gear tire went flat due to heavy braking.
- The flight crew demonstrated inadequate knowledge of the aircraft systems and flight procedures, as they could not identify the potential causes of the malfunction.
- The pilot training and proficiency check syllabus were insufficient, as they did not include aborted takeoff exercises.
Safety action
The NTSC recommended that PT Merpati Nusantara Airline improve recurrent training programs to ensure pilots fully understand aircraft systems. Additionally, the committee recommended that proficiency checks be updated to include specific exercises for aborted takeoff procedures.