What happened
On January 26, 2008, a Schweizer 269C-1, registration PT-YOG, was engaged in flight instruction at Edra Aeronáutica Aerodrome in Ipeúna, São Paulo. Following a series of completed autorotation exercises, the instructor initiated a simulated engine failure by partially reducing power after takeoff.
During the maneuver, the student pilot correctly managed the cyclic controls to maintain airspeed; however, during the flare, the student applied the collective control with excessive amplitude. This rapid input caused a critical loss of main rotor RPM. The resulting increase in the rate of descent prevented the instructor from recovering the aircraft, leading to the tail rotor striking the ground, followed by the skids, and a lateral overturn. Both the instructor and the student sustained minor injuries, but the aircraft suffered heavy damage.
The investigation
CENIPA investigators examined the flight parameters and the sequence of events leading to the impact. The investigation focused on the altitude and safety margins maintained during the critical training phase. While the student's performance in previous evaluations had been above average, the investigation noted that the simulation was conducted at an altitude of approximately 250 to 300 feet AGL, which was significantly lower than the recommended 500 feet AGL for such maneuvers.
Physical evidence at the scene included damage to the main rotor blades, specifically showing signs of the "coning effect," which occurs when centrifugal force and weight cause the blades to flex upward as rotor rotation decreases. The investigation also reviewed the instructor's management of the cockpit dynamics and the specific training profile used during the emergency simulation.
Findings
- Excessive collective input: The student pilot applied the collective control with too much amplitude, leading to the loss of rotor RPM.
- Insufficient safety margin: The training profile (simulated engine failure after takeoff) was conducted at an altitude that did not provide enough margin to correct student errors.
- Inadequate cockpit management: The instructor's management of the simultaneous procedures and dynamics during the emergency contributed to the inability to intervene effectively.
- Low rotor inertia: The low inertia of the main rotor contributed to the rapid loss of rotation following the improper control input.