What happened
On March 17, 2008, at approximately 14:30 UTC, a Robinson R22 helicopter, registration PT-YFV, was conducting a local instructional flight departing from Jacarepaguá Aerodrome (SBJR) in Rio de Janeiro, Brazil. The crew consisted of an instructor pilot and a student pilot.
While the aircraft was on the final approach for a touch-and-go maneuver on runway 20, the crew heard a loud bang. This was immediately followed by a sharp yaw to the right and a sudden pitch-up motion. The instructor attempted to compensate by applying left pedal, but the controls failed to respond. To avoid a more serious accident, the instructor initiated an autorotation, pitching the nose down to reach an empty field, where the aircraft performed a hard landing.
The impact resulted in substantial damage to the aircraft. Both occupants survived the occurrence without injuries.
The investigation
CENIPA investigators examined the wreckage and the flight history of the aircraft. While ground observers reported seeing what appeared to be feathers in the air following the noise, forensic testing using Luminol on the tail rotor blades showed no traces of blood, effectively ruling out a bird strike as the cause.
Technical analysis of the vertical and horizontal stabilizers, which were found detached on a nearby warehouse roof, revealed that the tail rotor blades had struck the lower part of the vertical stabilizer. Laboratory examinations of the fractured components at the Institute of Aeronautics and Space (IAE) identified the failure as being caused by an overload mechanism. No evidence of corrosion or pre-existing fatigue cracks was found in the fracture area.
Investigators also noted damage to the tail rotor guard. Although a 100-hour inspection had been performed sixteen days prior, the investigation focused on whether previous instructional landings might have caused subtle deformations or cracks in the tail cone structure, potentially leading to the misalignment of the tail rotor.
Findings
- The tail rotor blades struck the lower vertical stabilizer, causing the failure of the tail rotor drive assembly.
- The fracture in the stabilizer support was consistent with an overload failure.
- The tail rotor guard showed evidence of damage on its lower section.
- Inadequate maintenance or inspection of the tail rotor guard and tail cone structure may have allowed a structural weakness to go undetected.