On 8 March 2024, a Pilatus PC-6/B2-H4 aircraft, registered PK-SNE, was being operated by PT Smart Cakrawala Aviation (Smart Aviation) on a cargo flight from Tarakan (WAQQ) to Binuang (WAQG). The flight was conducted on single pilot operation.

Based on the filed flight plan the flight would follow Visual Flight Rules (VFR), the cruising altitude would be 8,500 feet, the flight route would be directed from Tarakan to Binuang, and the fuel endurance would be sufficient for three-hour flight.

During the flight preparation, the pilot received pictures that depicted the weather over Binuang was cloudy.

At 0825 LT, in daylight conditions, the aircraft departed Tarakan. On board of the aircraft were a pilot, an aircraft engineer of Smart Aviation, and cargo with a total weight of 583 kg.

At 0854 LT, the pilot reported to the approach controller that the aircraft was over Malinau at an altitude of 8,500 feet. The approach controller then instructed PK-SNE to monitor radio communication at a frequency of 122.9 MHz. This communication was the last recorded transmission from the PK-SNE at the approach controller radio frequency.

The flight was monitored by the Flight Operation Officer (FOO) at Tarakan and Malinau using a flight following system. At 0900 LT, PK-SNE transmitted the last position report in the flight following system, which indicated that the aircraft was about 12 NM northeast of Malinau or about 35 NM southeast of Binuang.

About 1000 LT, the Malinau FOO, who had been aware that the PK-SNE did not transmit its position report in the flight following, then contacted the Binuang resident. The Binuang resident advised the Malinau FOO that the aircraft had not landed at Binuang. The Malinau FOO then contacted Malinau air traffic control, and the Tarakan FOO contacted Tarakan air traffic control. Both air traffic controllers then contacted the PK-SNE pilot several times and asked the air traffic services unit near Binuang of the PK-SNE. All attempts to locate the PKSNE aircraft were unsuccessful, and search and rescue activities were activated.

On 9 March 2024, the aircraft was found on the ridge of the mountain at the coordinates of 343’29.60”N and 11556’24.04”E, with an elevation of about 4,800 ft, 5 NM southeast of Binuang on a bearing of 305°.

At the time of issuing this Preliminary Report, KNKT had not been informed of any safety actions taken by involved parties resulting from this occurrence. The KNKT issued safety recommendations to address the safety issues identified in this report. 

The investigation involved the participation of the Swiss Transportation Safety Board (STSB) of the Switzerland as the State of Design and Manufacture, the Transportation Safety Board (TSB) of the Canada as the State of Manufacture, and Bureau d’Enquêtes et d’Analyses pour la sécurité de l’aviation civile (BEA) as the State providing assistance. All agencies have appointed their accredited representatives and advisers to assist in this investigation in accordance with the provisions in ICAO Annex 13.