What happened
On August 10, 1999, at approximately 17:40, a Robinson R-22 helicopter, registration PT-YDB, was performing a recreational flight over the Guaíba River near Porto Alegre, Brazil. The aircraft had departed from the Aeroclube do Rio Grande do Sul carrying the pilot and one passenger.
During the flight, the pilot initiated a simulated autorotation maneuver. After climbing to approximately 300 feet, the pilot executed a 180-degree right turn and began a descent toward the water, heading directly into the setting sun. At the final stage of the maneuver, the helicopter lost control and collided with the surface of the river. The impact occurred at a low speed with a high sink rate. The aircraft submerged, resulting in severe damage to the main rotor, main transmission, tail cone, and tail rotor. Both occupants were able to abandon the aircraft and were rescued by a nearby fisherman; both remained uninjured.
The investigation
The CENIPA investigation focused on the operational decisions and environmental factors present during the maneuver. Investigators examined the aircraft's maintenance records, which showed the helicopter was within its inspection limits and had no mechanical failures. The carburetor was tested and found to be in good condition.
Environmental analysis revealed that the water surface was "mirror-like" and the sun was low on the horizon, creating conditions prone to visual illusions. The investigation also reviewed the pilot's background, noting that while he held a valid private pilot license, he had previously been cautioned by flight instructors for aggressive and unsafe flying maneuvers. The investigation also considered the aerodynamic possibility of the aircraft entering a vortex ring state (settling with power) during the final phase of the maneuver.
Findings
- Deficient Planning: The pilot chose an unsuitable area for training, performing the maneuver over water and directly facing the sun.
- Inadequate Altitude: The flight was conducted below the minimum VFR altitude of 200 feet AGL, contrary to both air traffic regulations and the Robinson R-22 operating manual.
- Visual Illusions: The combination of the sun's glare and the reflective, calm water surface likely caused a loss of depth perception and height perception, leading to an improper flare.
- Flight Indiscipline: The pilot intentionally performed maneuvers that deviated from the manufacturer's operating manual and established safety standards.
- Psychological Factors: The pilot's decision-making was influenced by excessive self-confidence and a desire for self-affirmation through demonstrating the aircraft's capabilities.
Safety action
CENIPA issued several recommendations to the Civil Aviation Department and Regional Services, including:
- Implementing more detailed flight evaluation forms for the validation of foreign licenses.
- Mandating lectures on human factors, specifically regarding judgment and decision-making errors, in flight safety seminars.
- Requiring helicopter check pilots to evaluate operational and human factors identified in recurring R-22 accidents during check flights.