What happened
On August 22, 2003, an SK-76A helicopter, registration PT-YAU, was performing a periodic training flight at Macaé Airport (SBME) in Rio de Janeiro. The mission involved a monthly emergency procedure refresher, specifically practicing a "square" maneuver with a constant heading. For this training, the Automatic Flight Control System (AFCS) was intentionally deactivated.
During the exercise, while the aircraft was in a backward flight phase, the pilot in training experienced significant difficulty managing the helicopter due to surface winds. The aircraft's attitude began to fluctuate abnormally. As the pilot attempted to correct the position, the nose pitched down sharply and abruptly. The instructor attempted to take control, but the crew engaged in simultaneous and conflicting control inputs. This led to a loss of control, causing the main rotor blades to strike the ground. The aircraft subsequently overturned and came to rest approximately 25 meters from the initial impact site. Both crew members survived the accident without injuries, though the helicopter was a total loss.
The investigation
CENIPA's investigation focused on the mechanical, meteorological, and human factors involved in the loss of control. Investigators confirmed that the aircraft's hydraulic and flight control systems were fully operational and that all maintenance records and inspections were up to date. The investigation also reviewed the Cockpit Voice Recorder (CVR) from the NTSB laboratories, which revealed that the student pilot had verbally expressed difficulty managing the aircraft due to the wind, but the instructor's intervention was delayed.
Technical analysis determined that while the aircraft remained controllable without the AFCS, the specific training maneuver—performing high-power, low-altitude maneuvers in a confined space with the system off—created an unnecessarily high level of difficulty. The investigation also noted that the instructor's reliance on the student's perceived proficiency contributed to the delay in taking decisive action.
Findings
- Wind conditions: Prevailing winds increased the difficulty of the flight maneuvers, contributing to the pilot's struggle with the aircraft.
- Pilot experience: While both pilots were highly experienced in rotary-wing aviation generally, they possessed limited experience specifically with the SK-76A model.
- Crew coordination: There was a lack of assertive communication from the student pilot and a failure by the instructor to recognize the severity of the student's difficulty early enough.
- Control inputs: The occurrence of simultaneous and conflicting control inputs between the instructor and the student pilot led to a divergent flight path.
- Training design: The training maneuver (square pattern with AFCS off) was more demanding than a real-world AFCS failure scenario, which would typically involve a direct landing rather than complex maneuvering.
Safety action
Following the investigation, CENIPA issued several safety recommendations:
- Training modifications: Instructors should deactivate the AFCS during training while on the downwind leg or outside the traffic pattern to ensure sufficient vertical and horizontal clearance from obstacles.
- Standardization: Offshore air taxi operators were advised to standardize training programs and implement better oversight regarding instructor and student proficiency levels.
- Instructor training: Recommendations were made to improve instructor standardization through both theoretical and practical training to ensure effective supervision during high-difficulty maneuvers.