What happened
On the morning of September 7, 2002, a Robinson R-22 helicopter, registration EC-GVR, was operating at the Brunete ultralight airfield in Madrid. After arriving from Cuatro Vientos, the pilot and one passenger prepared for a subsequent takeoff. Following the pre-flight checks and engine start, the pilot transitioned the aircraft into a hover.
During this hover phase, the aircraft began to rotate rapidly to the right. The pilot attempted to regain control, but the aircraft also began to tilt laterally. In an effort to stabilize the aircraft, the pilot reduced the main rotor pitch by lowering the collective lever. This action decreased lift, causing the aircraft to descend abruptly and land on the ground in a level but forceful attitude. The impact resulted in a broken rear crossbar and damage to the landing skids. Both occupants were uninjured.
The investigation
The investigation focused on the aerodynamic conditions present during the takeoff phase. Investigators examined the interaction between wind conditions and the helicopter's single main rotor system. The analysis considered how specific wind sectors can lead to a loss of tail rotor effectiveness (LTE), where the tail rotor is unable to provide sufficient thrust to counteract the torque generated by the main rotor.
Findings
- The primary cause of the incident was loss of tail rotor effectiveness induced by specific wind conditions.
- For helicopters with a counter-clockwise main rotor rotation, certain wind directions—specifically winds between 285º and 315º or tailwinds between 120º and 240º—can trigger uncommanded yaw or rapid rotation.
- In this instance, the wind conditions caused the tail rotor to lose its ability to compensate for the engine's torque, leading to the uncontrolled rightward yaw.
- The pilot's decision to reduce collective pitch to mitigate the rotation led to a hard landing, causing structural damage to the airframe.