What happened
On 25 April 2012, a Pilatus PC-6/ B2-H4 Turbo Porter, registration PK-VVQ, was conducting an aerial survey flight over the Melak area in East Kalimantan, Indonesia. The aircraft, operated by PT. ASI Pujiastually Aviation (Susi Air), departed from Balikpapan with one pilot and one passenger on board.
During the mission, the engine experienced a flameout. Shortly before the aircraft went down, the passenger sent a text message to an employer stating that the aircraft had run out of fuel and was attempting to land on a road. The aircraft subsequently impacted the ground near the village of Muaritan. The impact was characterized by extreme deceleration, making the crash unsurvivable. Both the pilot and the passenger sustained fatal injuries.
The investigation
The investigation focused on the aircraft's fuel system and the circumstances leading to the engine failure. Investigators found that while the auxiliary fuel tanks were still full, the main fuel tanks had been depleted. The fuel transfer process from the external tanks to the main tanks had not been completed.
Technical analysis of the wreckage revealed that the propeller was in a feathered position at the time of impact. The investigation also noted that the aircraft's horizontal pitch trim was set to a nearly full nose-up position and the flaps were only partially extended. Furthermore, it was determined that the pilot's shoulder harness was not in use at the time of the accident.
Findings
Several contributing factors were identified in the sequence of events:
- The engine flameout was directly caused by a lack of fuel supply to the engine because the main tanks had run dry.
- The failure to transfer fuel from the auxiliary tanks to the main tanks was the primary mechanical cause of the fuel exhaustion.
- The pilot, who had relatively little experience with this specific aircraft type and was in the early stages of transition to survey flying, likely became fixated on the high-precision demands of the survey mission.
- This fixation, combined with fatigue and the demanding nature of the survey operations, led to a loss of situational awareness regarding the aircraft's fuel state.
- The low altitude of the survey flight (between 1,500 and 2,500 feet) left the crew with insufficient time or suitable terrain to execute an emergency landing.
Safety action
Following the accident, the operator, PT. ASI Pujiastually Aviation, implemented new Standard Operating Procedures (SOP) for survey flights. These procedures include enhanced fuel management protocols, site-specific risk analysis, and comprehensive training programs for new pilots. Additionally, a recommendation was made to Pilatus Aircraft Ltd. to consider the development of a low-fuel warning system for the PC-6 series.