What happened
On 23 December 2022, a DHC-6-300 Twin Otter, registration PK-OTY, operated by PT. Rimbun Abadi Aviasi, was performing an unscheduled cargo and passenger flight in Papua, Indonesia. After completing several successful sectors, the crew decided to divert to Moanamani Airport.
While approaching the field, the pilot decided to land on Runway 03 instead of the originally planned Runway 21 to expedite the process, noting that the wind appeared calm. Upon touchdown on Runway 03, the pilot engaged the propeller reverse thrust. Shortly after, the aircraft began drifting toward the right side of the runway. The pilot attempted to correct the deviation using left rudder, temporarily realigning the aircraft with the centerline. However, as the aircraft passed the apron area, it skidded further to the right. The aircraft exited the paved surface, struck an airport fence, and the right main wheel entered a ditch, causing the nose gear to collapse. The crew and an engineer evacuated the aircraft without fatalities, though two crew members sustained minor injuries.
The investigation
The KNKT investigation focused on the sequence of events leading to the loss of directional control. Investigators examined the aircraft's maintenance records, which showed no prior issues with the nose wheel steering system. The investigation also reviewed the pilot's training history, noting that while the pilot in command was experienced, this was their first landing at Moanamani since joining the operator.
Technical reviews of the aircraft's documentation revealed that the Quick Reference Handbook (QRH) used by the crew had not been updated to include recent manufacturer amendments regarding the nose wheel steering lever. Furthermore, the Cockpit Voice Recorder (CVR) did not capture the performance of the Approach Checklist during the final stages of the flight.
Findings
- The pilot decided to change the landing runway without a recorded discussion between the crew members.
- The aircraft's QRH lacked updated nose wheel steering procedures, which required a specific physical check (applying upward and downward pressure) to confirm the steering lever was properly locked in the center position.
- The crew did not perform the Approach Checklist as recorded by the CVR, which could have impacted airspeed management.
- The pilot's recent training history included remarks regarding directional control and speed management.