What happened
On November 21, 2019, a Bell 407 helicopter, registration PR-SLO, was performing training maneuvers at Campo de Marte Airport (SBMT) in São Paulo, Brazil. The flight had departed from Heliponto Wheaton in São Bernardo do Campo to transport a passenger and conduct emergency procedure training.
The pilot had successfully completed seven autorotation maneuvers without incident. However, during the eighth attempt, the aircraft experienced an abnormal contact with the runway. The pilot executed the flare at an altitude lower than recommended and at a low airspeed of approximately 2/20 kt. This resulted in the tail skid striking the ground, which caused the main rotor blades to collide with the tail rotor drive shaft and the horizontal stabilizer.
Following the hard landing, the pilot attempted a subsequent takeoff. During this attempt, the aircraft rotated approximately 270 degrees on its axis before coming to a stop. Despite the impact, the pilot initially informed Air Traffic Control that no damage had occurred, unaware that the tail rotor drive shaft had been severed.
The investigation
CENIPA's investigation focused on the execution of the maneuver and the pilot's situational awareness. The investigation confirmed that the pilot was fully qualified with recent experience in the aircraft type and that the Bell 407 was airworthy and within weight and balance limits. No mechanical failures or system malfunctions were identified as contributing to the event.
Investigators analyzed the flight dynamics of the flare maneuver, noting that at speeds below 45 kt, the flare is less effective at reducing the rate of descent. The investigation also highlighted that the training was being conducted without the presence of a flight instructor. Furthermore, the investigation noted a lack of situational awareness, as the pilot attempted a second takeoff without realizing the structural integrity of the tail rotor system had been compromised by the initial impact.
Findings
- The pilot executed the flare at an insufficient altitude and airspeed.
- The tail skid struck the ground, leading to the main rotor blades striking the tail structure.
- The tail rotor drive shaft was severed during the collision.
- Improper application of flight controls during the final phase of the maneuver contributed to the hard landing.
- The training was performed without an instructor on board.
- The pilot's failure to perceive the structural damage led to an unsafe attempted takeoff.