What happened
On September 21, 2016, an AT-602 aircraft, registration N1001R, was performing a ferry flight from São José dos Campos to Mirassol, Brazil. The flight was part of a complex delivery operation to transfer the aircraft from the United States to a buyer in Brazil.
During the descent phase, approximately 10 nautical miles from the Mirassol Aerodrome, the engine experienced a significant malfunction. The pilot attempted to increase power, but the engine failed to respond, with the power turbine rotation dropping to 70%. Unable to maintain flight, the pilot executed an emergency landing in a sugarcane field at the Santa Inês Farm. The aircraft sustained substantial damage to the wings, fuselage, landing gear, and stabilizers, but the pilot escaped the wreckage unharmed.
The investigation
CENIPA investigators examined the aircraft's engine, a Pratt & Whitney Canada PT6A-60AG, and analyzed data from the onboard engine monitoring system. Testing conducted by the manufacturer in Canada revealed that the Fuel Control Unit (FCU) was malfunctioning due to the presence of debris.
Investigators found significant amounts of contaminants, including fiberglass, zinc stearate, and traces of an amine compound, within the aircraft's fuel filter, fuel pump, and the FCU itself. While the fuel samples themselves showed no contamination, the high concentration of debris in the airframe's filters suggested the source was the fuel delivery system. The investigation focused on a temporary fuel system installed for the ferry flight, which utilized the aircraft's hopper as an auxiliary fuel tank.
Findings
- The primary cause of the engine power loss was contamination within the fuel control unit (FCU) and fuel pump.
- The use of the aircraft's hopper as an uncertified, temporary fuel tank likely introduced debris into the fuel system.
- The presence of fiberglass and zinc stearate suggests the contamination originated from the hopper, which is typically used for transporting agricultural products and may not meet the cleaning standards required for aviation fuel storage.
- The aircraft was operating outside of its authorized route during the transfer flight.