What happened
On 12 July 2023, a Pilatus PC-6/B2-H4, registered PK-VVU, was performing a cargo flight from Tarakan to Long Layu Airstrip in North Kalimantan, Indonesia. The flight, operated by PT Asi Pudjiastuti Aviation (Susi Air), was delayed by two hours to allow a recently wet runway to dry.
During the approach to Runway 19, the pilot performed an overhead maneuver to assess the runway conditions. To ensure better directional control and a longer landing distance on the potentially slippery surface, the pilot chose an approach path with an offset of less than 15 degrees. This deviation from the standard 15-degree offset—intended to avoid trees on the short final path—resulted in the aircraft's right wing striking tree branches. While the aircraft sustained a dent on the leading edge of the right wing, the pilot landed safely and no injuries were reported.
The investigation
The investigation by the KNKT focused on the pilot's decision-making and the adequacy of available aeronautical information. The inquiry established that the aircraft was airworthy and operating within weight and balance limits, and that weather conditions were clear with good visibility.
Investigators examined the Area Reference Booklet (ARB) used by the operator, finding that while the presence of trees was noted, the document lacked detailed approach procedures for Long Lay0 Airstrip. Furthermore, the investigation found that the airstrip, managed by local government, lacked formal registration with the DGCA, meaning the airstrip operator was not formally required to implement a hazard identification system. Consequently, the tree was not identified as a specific hazard by the operator until after the incident occurred.
Findings
- The pilot's decision to use a reduced approach offset to manage runway surface conditions led to the wing strike.
- There was an absence of detailed, documented approach procedures for Runway 19 in the operator's Area Reference Booklet.
- Unmitigated vegetation near the runway created a significant operational risk.
- The airstrip operator was unaware of the tree as a specific hazard due to the lack of a formal hazard reporting and management system at the site.
Safety action
In response to the incident, Susi Air implemented several safety measures, including conducting refresher training for the pilot covering performance, safety awareness, and human factors. The operator also requested that the airstrip operator trim the encroaching branches and has increased safety promotion activities to encourage more frequent hazard reporting by flight crews.