What happened
On April 25, 2001, at approximately 13:10 local time, a Bell 206 helicopter, registration PT-HXZ, departed from Heliponto Tamboré in Barueri, São Paulo, for a local leisure flight. The aircraft was carrying four occupants, including the pilot, who was also the owner.
Shortly after takeoff, the engine experienced a sudden loss of power. Witnesses observed the aircraft entering a descending right-hand turn as the pilot attempted an autorotation maneuver. The helicopter struck the roof of an Atlas Copco industrial warehouse. The impact ruptured the fuel tank, and electrical sparks from severed wiring in the building ignited the leaking kerosene. The resulting intense fire completely destroyed the aircraft and caused the deaths of all four occupants.
The investigation
CENIPA investigators reconstructed the wreckage at the IFI/CTA laboratory to analyze the engine and components. The investigation focused on the cause of the engine flameout. Analysis of the engine revealed that the N1 and N2 turbines were functional, but the compressor was seized due to fire damage.
Detailed examination of the fuel system identified debris in the airframe fuel filter, the engine fuel pump filter, and the fuel nozzle filter. Specifically, the fuel nozzle filter showed signs of deformation caused by a pressure differential. Testing at Rolls Royce in the United States confirmed that the fuel nozzle filter had collapsed due to an obstruction. Furthermore, investigators found that the turbine governor and fuel nozzle had serial numbers that did not match the aircraft's maintenance logs, suggesting undocumented part replacements.
Findings
- The engine flameout was caused by a momentary interruption of fuel flow due to the clogging and subsequent collapse of the fuel nozzle filter.
- Severe fuel contamination, including sand, clay, and water, was present in the fuel system, likely introduced during previous refueling.
- Maintenance performed by the maintenance facility was inadequate; while the fuel tank had been cleaned, the required inspection and cleaning of the engine fuel lines and filters were not performed as mandated by the manufacturer's manual.
- The pilot's lack of recent flight experience in this specific aircraft type contributed to errors in executing the emergency autorotation maneuver.
- Deficient judgment was noted when the pilot attempted to fly past the warehouse during the autorotation attempt, failing to properly account for altitude and airspeed.