What happened
On February 11, 1998, a Hughes 369 HS helicopter, registration PT-HFF, was performing herbicide spraying operations over sugarcane plantations at Engenho Cusaí, near Carpina, Pernambuco. During the mission, the pilot performed a series of maneuvers that included an intermediate refueling stop and a period of waiting for ground markers to be positioned.
While executing a right-hand turn to approach a landing site, witnesses observed the engine noise decrease significantly before the aircraft lost altitude and struck the ground. The impact caused severe damage to the airframe, engine, rotors, transmission, and tail cone. The pilot sustained serious injuries.
The investigation
CENIPA investigators examined the wreckage and the engine, finding no evidence of mechanical failure or material defects that could have caused the power loss. The investigation focused on the operational procedures and the pilot's fuel management.
Records showed that the pilot had a habit of flying with lower fuel levels than company policy dictated, often requesting only 100 pounds of fuel to keep the aircraft light and save time. At the time of the crash, only 13 pounds of fuel remained in the tanks. The investigation also noted that the pilot was flying at a low altitude and low airspeed, specifically within the high-risk parameters of the aircraft's "Dead Man's Curve" (height-velocity diagram), which significantly reduced the chances of a successful autorotation following the engine failure.
Findings
- Excessive self-confidence: The pilot's overconfidence led to a disregard for company refueling guidelines and a failure to monitor fuel levels via the liquidometer, relying instead on estimated flight time.
- Deficient judgment and planning: The pilot's decision to perform low-altitude, low-speed maneuvers while operating with critically low fuel levels was a primary contributing factor.
- Lack of operational supervision: The operator failed to implement oversight mechanisms to ensure the pilot adhered to the established refueling protocols, despite being aware of the non-compliance.
- Operational risks: The pilot's practice of flying with reduced fuel to increase efficiency and save time directly contributed to the engine flameout during a high-bank turn.