What happened
On 24 August 2012, a Piper Chieftain PA31-350, registration PK-IWH, departed from Temindung Airport (WALS) in Samarinda at 0751 local time. Operated by PT. Intan Angkasa Airservice, the aircraft was performing an aero magnetic survey north of Bontang, East Kalimantan. The crew, consisting of one pilot, one security officer, and two surveyors, had planned to fly at 3,000 feet AMSL en-route and descend to 500 feet AGL for the survey operations.
During the flight, the pilot communicated with the Temindung Control Tower, reporting that the aircraft was passing Tanjung Santan while descending from 3,000 feet. The pilot then established contact with the Bontang Info officer, stating the aircraft was at 300 feet altitude and providing an estimated time of arrival over Bontang. However, at 0010 UTC, the flight following system, SureTrack, lost all data from the aircraft. The final recorded telemetry indicated a speed of 138 knots on a heading of 352°.
Concern arose at 0600 UTC when an engineer noted that the aircraft had exceeded its planned fuel endurance. After unsuccessful attempts to reach the pilot via Bontang Info and Tanjung Bara Airstrip, authorities transitioned through the uncertainty, alert, and distress phases (INCERFA, ALERFA, and DETRESFA) between 0610 and 0700 UTC. A multi-agency search and rescue operation involving ground teams and three helicopters was launched at 0730 UTC.
On 26 August 2012, a ground search team discovered the wreckage on a ridge of Mayang Hill, approximately 1,200 feet AMSL. The site was located roughly 12 NM from Bontang Aerodrome, within the intended survey area. The impact and subsequent fire resulted in four fatalities and the total destruction of the aircraft.