What happened
On September 27, 1998, an R-22 helicopter, registration PT-HXQ, departed from Heliponto Tamboré in Barueri, São Paulo, for a sightseeing flight over the Billings Reservoir. The flight, which included the pilot and one passenger, was conducted without a prior flight plan or notification.
As the pilot attempted to land near the reservoir, the aircraft entered a left turn at an altitude of approximately 250 feet and a speed of 30 knots. During this maneuver, the helicopter experienced a loss of directional control and began spinning to the right. In an attempt to recover, the pilot increased power, which triggered the engine's intake pressure warning and further destabilized the aircraft. The pilot subsequently lowered the collective to enter autorotation; however, the altitude was insufficient to prevent the main rotor blades from striking a tree. The aircraft subsequently struck the ground with a level attitude, resulting in severe damage to the airframe, engine, and rotor systems. Both occupants escaped the crash uninjured.
The investigation
CENIPA's investigation focused on the meteorological conditions, the pilot's experience, and the operational procedures followed during the approach. Investigators noted that the pilot was qualified but possessed limited experience in this specific aircraft type, with only 150 total flight hours.
Meteorological data revealed that a passing cold front was causing high temperatures (31°C) and significant wind instability, with sustained winds of 10 knots and gusts reaching 28 knots. The investigation also examined the aircraft's manual, which strictly prohibits operations when surface gusts exceed 25 knots or when wind variance exceeds 15 knots. Furthermore, the pilot's approach altitude of 250 feet was found to be below the 500-foot minimum required for traffic in areas without air traffic control.
Findings
- Adverse Meteorological Conditions: The presence of wind gusts up to 28 knots exceeded the operational limits defined in the Robinson R-22 manual.
- Loss of Tail Rotor Effectiveness: During the left turn, the wind direction change caused a loss of tail rotor efficiency, leading to the uncontrolled rightward yaw.
- Improper Recovery Technique: Instead of applying forward cyclic and lowering the collective to restore control, the pilot increased power, which exacerbated the loss of control and led to a vortex ring state condition.
- Operational Deviations: The pilot failed to notify authorities of the flight, operated below the regulatory minimum altitude, and disregarded the aircraft's wind limitations.
- Pilot Experience and Judgment: The pilot's limited experience in the R-22 and a lack of adequate weather planning contributed to the decision to fly in unstable conditions.