What happened
On May 3, 2021, at approximately 16:30 UTC, a Robinson R22 helicopter, registration PT-HUD, was conducting a local flight training mission at Aeródromo Campo de Marte (SBMT) in São Paulo, Brazil. The flight was being conducted by an instructor and a student pilot as part of a private pilot helicopter training program.
After completing several standard maneuvers, the instructor decided to demonstrate a takeoff and landing procedure on sloped terrain. The crew moved to a grassy area characterized by a lateral slope of approximately 9 degrees. During the maneuver, the helicopter's left skid remained in contact with the ground while the right skid was elevated. As the aircraft attempted to maneuver, it experienced a lateral roll to the left, leading to a dynamic rollover and subsequent collision with the ground. The impact caused substantial damage to the aircraft, though both occupants sustained only light injuries.
The investigation
CENIPA investigators examined the aircraft, the site, and the flight records. The investigation confirmed that the weather conditions were favorable for visual flight rules (VFR) and that both pilots held valid medical certificates and necessary licenses. The aircraft's airworthiness certificate was valid, and the aircraft was within weight and balance limits.
Investigators analyzed the terrain and found no external objects or obstructions that could have snagged the skid. The investigation focused on the physics of the rollover, noting that the 9-degree slope exceeded the 5-degree maximum inclination recommended in the Robinson R22 Maneuver Guide for such training operations. Furthermore, the investigation found that the instructor had not conducted a specific briefing for this particular slope maneuver prior to the execution.
Findings
- The primary cause of the accident was a dynamic rollover triggered by inappropriate control inputs and the exceeding of the critical roll angle.
- The pilot applied full collective power during the onset of the roll, which increased the angular momentum and contributed to the instability.
- The terrain slope of 9 degrees exceeded the manufacturer's recommended limit of 5 degrees for slope operations.
- There was a lack of a specific briefing for the student regarding the intended slope maneuver.
- The engine logbook entries were found to be out of date according to regulatory requirements.