What happened
On April 16, 2003, an R22 BETA helicopter, registration PT-YBF, was conducting a local flight training mission near Mogi das Cruzes, Brazil. The flight was intended to assist a private pilot in transitioning back to active flying in preparation for a commercial pilot checkride.
During the second approach to a landing area, the pilot attempted to reduce the rate of descent by increasing collective pitch. This action triggered significant vibrations and an abnormal rate of sink. The crew attempted to regain control, but the aircraft entered a state of uncontrolled descent, performing a 1/2 turn before the left skid struck the ground. Both occupants survived the impact without injuries, but the aircraft sustained severe damage and was determined to be a total loss.
The investigation
CENIPA investigators examined the flight profiles, maintenance records, and crew qualifications. The investigation focused on the aerodynamic conditions during the approach and the crew's response to the onset of instability. Investigators analyzed the impact site, a golf course near a reservoir, and reviewed the aircraft's engine and rotor performance. While investigators considered the possibility of carburetor icing due to the proximity to a body of water, environmental data ruled this out. The investigation also looked into the training school's procedures and the instructor's management of the student during the maneuver.
Findings
- The aircraft entered a vortex ring state during a high-angle approach.
- The approach was conducted with a tailwind component, which delayed the movement of the turbulent wake and exacerbated the loss of lift.
- The crew failed to account for the degradation of engine performance caused by high density altitude and high temperatures.
- The instructor demonstrated poor judgment and delayed intervention, failing to take control effectively when the student's inputs led to an unrecoverable situation.
- There was a lack of coordination and assertiveness between the instructor and the student during the emergency.
- The flight training school's procedures deviated from the manufacturer's manual, specifically regarding approach angles and tailwind operations.