What happened
On 15 October 2020, a PAC 75 and XL aircraft, registration PK-RWR, was performing an unscheduled cargo and passenger flight from Nabire to the Bayabiru Airstrip in Papua, Indonesia. During the approach, the crew noted a tailwind of approximately 5 knots. Because the runway is a grass surface, the pilots could not visually confirm if the surface was wet or dry; however, based on unofficial weather reports suggesting only light morning drizzle, they proceeded with the landing.
Upon touchdown, the crew found the runway to be slippery. The pilot flying applied maximum braking and moved the propeller to Beta Mode to slow the aircraft, but deceleration was insufficient. The pilot in command then took control and engaged reverse thrust. Despite these efforts, the aircraft overran the runway and struck higher ground at the end of the airstrip. There were no injuries among the occupants, though the aircraft sustained substantial damage.
The investigation
The KNKT investigation focused on the decision-making process regarding weather and the physical conditions of the airstrip. Investigators found that the pilot obtained weather information via a mobile messaging application from a local resident in Bayabiru. This resident, who lacked meteorological training, provided information based on personal observations from a distance. The pilot assumed the morning drizzle had dried by the time of arrival, but the runway remained slick.
Furthermore, the investigation revealed that the Bayabiru Airstrip is not certified by the Directorate General of Civil Aviation and its details are not included in the Aeronautical Information Publication. While the operator's internal charts listed a runway length of 350 meters, investigators measured the actual usable distance to be only 330 meters due to encroaching vegetation.
Findings
- The primary cause of the overrun was the slippery runway surface which prevented effective deceleration.
- The crew relied on unreliable weather information provided by an unqualified local resident rather than official meteorological sources.
- The pilot's decision to fly was based on the assumption that the runway had dried, which proved incorrect.
- The aircraft's weight and balance calculations were inaccurate because they were based on a two-seat configuration rather than the actual four-seat installation.
- The use of an outdated TIBA frequency by air traffic control created potential communication risks in the uncontrolled airspace.
Safety action
- The KNKT recommended that Tariku Aviation implement procedures to ensure pilots obtain accurate runway condition data.
- The operator was advised to ensure weight and balance calculations reflect the actual aircraft configuration.
- A recommendation was made to AirNav Indonesia to review radio frequency usage in uncontrolled areas to prevent communication gaps between aircraft.