What happened
On 22 September 2011, a Pilatus PC-6/B2-H4, registration PK-UCE, operated by Yayasan Jasa Aviasi Indonesia (YAJASI), crashed in the North Gap corridor near the Pass Valley airstrip in Papua. The flight departed Pagai at 0403 UTC, bound for Wamena, and was flying under Visual Flight Rules (VFR) at a cruise altitude of 10,000 feet.
At 0413 UTC, the pilot transmitted a position report to the flight following officer at Sentani Airport. However, following this transmission, no further radio contact or updates were received. When the aircraft failed to arrive at its destination by the estimated time, a search was initiated involving other YAJASI aircraft and local pilots. The wreckage was eventually located in a mountainous area at an elevation of approximately 7,500 feet, where the aircraft had struck trees and the ground. The accident resulted in 3 fatalities.
The investigation
The investigation by the NTSC focused on the pilot's decision-making and the meteorological conditions at the time of the accident. Investigators examined the aircraft's flight path through the North Gap corridor and reviewed the weather reports from Wamena Airport, which indicated intermittent rain and scattered clouds.
Technical analysis of the wreckage showed that the propeller blades were bent rearward and the left wing was broken. The investigation also reviewed the regulatory requirements for VFR flight in Class F airspace, which mandates specific visibility and cloud clearance distances. Furthermore, the investigators looked into the company's training protocols and the status of official visual flight guidance in the region.
Findings
- The pilot made the decision to descend from 10,000 feet to penetrate an area of marginal weather, a maneuver that was likely more dangerous than perceived.
- To avoid cloud formations located to the left of the established VFR route, the pilot maneuvered into a space that did not meet the required weather minimums for Class F airspace.
- The aircraft was unpressurized, and the impact occurred at 7,500 feet, near the limits of the pilot's safe operating altitude without supplemental oxygen.
Safety action
Following the accident, YAJASI implemented several training enhancements, specifically focusing on pilot decision-making in mountainous terrain. These updates emphasize the importance of aborting flights when encountering challenging weather and maintaining adequate visibility margins to allow for safe maneuvering at higher altitudes. Additionally, the NTSC recommended that the Indonesian Directorate General of Civil Aviation expedite the official issuance of a standard Visual Flight Guide (VFG) to provide clear, regulated routes for VFR operations in the growing Papua aviation sector.