What happened
On March 23, 2008, an EMB 202A aircraft, registration PT-UUC, was performing agricultural spraying operations in Primavera do Leste, Mato Grosso, when the engine experienced a significant loss of power. Approximately 20 minutes into the mission, the pilot attempted emergency procedures, but the engine failed to restart. After jettisoning the chemical load, the pilot executed a forced landing into a cornfield.
The pilot escaped the aircraft uninjured, though the aircraft sustained severe damage to the propeller, engine, landing gear, and the agricultural application equipment.
The investigation
CENIPA investigators determined that the engine failure was caused by the failure of the mechanical fuel pump. Bench tests revealed that the pump was unable to generate pressure because the central shaft had detached from the engine-driven actuation lever. This specific failure mode had been documented in three previous similar cases.
Furthermore, the investigation found that although the aircraft's operating manual requires the auxiliary electric fuel pump to remain active during agricultural operations, the pilot had deactivated it shortly after takeoff. While the pilot attempted to restart the engine by engaging the electric pump, the engine failed to ignite. Subsequent inspections of the magnetos revealed they were operating outside of normal parameters, with significant wear and rust on a bushing, which prevented proper ignition even when fuel was available.
Findings
- Mechanical Failure: The mechanical fuel pump's central shaft ruptured, cutting off fuel flow.
- Maintenance Deficiencies: The magnetos had exceeded their recommended service intervals, having operated for approximately 600 hours without maintenance, whereas they should have been inspected every 100 hours and replaced every 300 hours.
- Operational Error: The pilot deactivated the auxiliary electric fuel pump to prevent perceived wear, a practice driven by a common professional culture among agricultural pilots that contradicts the manufacturer's manual.
- Design/Service Factors: The investigation noted that the mechanical pump design required updated replacement intervals to prevent similar shaft ruptures.