What happened
On the afternoon of 30 April 2009, a Beechcraft Sundowner C23, registration PK-ANW, was conducting a local training flight near Budiarto Airport, Indonesia. The aircraft was operated by Sekolah Tinggi Penerbangan Indonesia (STPI) with one flight instructor and two student pilots on board.
During the flight, the air traffic controller notified the crew of deteriorating weather, including heavy rain and thunderstorms in the area, and advised them to return to the aerodrome. However, the crew elected to continue their training in a different area due to reduced visibility. While attempting to return to Budiarto Airport, the aircraft encountered intense thunderstorms, heavy rain, and strong winds. The aircraft subsequently impacted the ground at Tenjo Village, approximately 13 km southwest of the airport. The impact resulted in one fatality and two serious injuries.
The investigation
The investigation focused on the aircraft's flight path, the meteorological conditions, and the operational procedures of the flight school. Investigators examined the wreckage and determined the damage was consistent with an aerodynamic stall at the time of impact. A passenger in the rear seat reported experiencing a strong downdraft and hearing the aircraft's stall warning before the crash.
Regarding the occupants, the investigation found that the instructor was not wearing the shoulder section of his safety harness, which likely contributed to his fatal injuries. Furthermore, the serious injuries sustained by the rear passenger were attributed to an improperly fastened seat belt. The investigation also looked into the communications equipment at Budiarto Airport, noting that the controller was using a portable VHF transceiver due to the unserviceability of the primary system.