What happened
On January 22, 2002, a Pilatus PC-6/B2H2, registration OB-1600, operated by Aero Andino S.A., departed from Pucallpa for a commercial flight to Atalaya. While cruising at approximately 9,000 feet, roughly 82 miles from Pucallpa, the aircraft's Pratt & Whitney PT6A-27 engine suffered a loss of power, preventing the aircraft from maintaining altitude.
As the aircraft descended at a rate of 800 to 1,000 feet per minute, the pilot attempted to reach the nearest alternate aerodrome at Nueva Italia, Cumaria. However, due to the inability to maintain altitude and the distance from the alternate, the pilot began searching for a suitable landing site. After determining that a nearby island was unsuitable for a safe forced landing, the pilot identified a 50 by 50-meter patch of sugarcane field. The aircraft performed a full stall landing within approximately 20 meters. There were no fatalities among the crew or the nine passengers on board, though the aircraft sustained major damage.
The investigation
The investigation focused on the mechanical failure of the Pratt & Whitney PT6A-27 engine. Technical analysis of the engine components revealed that the loss of usable power was triggered by a structural failure within the compressor turbine. Furthermore, investigators examined the secondary failure of the P3 pneumatic line, which was impacted by vibrations and imbalances following the initial engine damage.
Findings
- The primary cause of the accident was the loss of usable power in the engine due to a creep fracture and subsequent detachment of one or more compressor turbine blades.
- The departing turbine blades impacted adjacent engine components, causing further deterioration and a significant drop in engine performance.
- The loss of turbine blades induced vibrations and imbalances that caused a fracture in the P3 pneumatic line.
- The fracture of the P3 line led to the malfunction of the Fuel Control Unit, which prevented the pilot from controlling engine power and caused the engine to default to minimum output.