What happened
On May 7, 2001, a Bell 407 helicopter, registered in Denmark, was performing a repositioning flight from Nuremberg to Zell am See. Due to weather conditions, the pilot diverted to Salzburg Airport, conducting the approach under Visual Flight Rules (VFR).
During the final approach to Runway 16, at approximately 50 meters above ground level and a speed of 90 KIAS, the pilot increased engine power and noticed a loss of tail rotor effectiveness, preventing complete torque compensation. Simultaneously, a yellow warning light illuminated, though the pilot was unable to identify the specific alert. Despite the pilot attempting to manually release the pedal restrictor control system via the emergency pedal stop release, the "ENGAGE" light remained illuminated.
As the pilot transitioned to a hover over Taxiway LIMA at approximately 10 KIAS, the aircraft began to yaw uncontrollably to the right due to the counter-clockwise rotation of the main rotor system. Unable to arrest the increasing yaw even with full left pedal input, the pilot initiated an emergency landing by reducing engine power to relieve torque. The helicopter subsequently performed a hard landing in the grass between Taxiway LIMA and the airport perimeter fence after completing approximately one and a regular half rotations.
There were no fatalities and no injuries to the crew, though the aircraft sustained significant damage, including a bent landing gear and a broken front skid cross tube.
The investigation
The investigation focused on the mechanical state of the tail rotor control system following recent maintenance. The aircraft had recently undergone scheduled inspections and maintenance on the tail rotor control linkage by a maintenance facility in Nuremberg. Following the accident, investigators examined the tail boom assembly.
Findings
- The primary cause of the loss of directional control was a mechanical disconnection between the control rod (ROD ASSY P/N 406-012-129-101) and the bellcrank (BELLCRANK ASSY P/N 406-001-704-101).
- This disconnection prevented the pilot's pedal inputs from effectively modulating the tail rotor pitch.
- The pilot's attempt to manually override the pedal restrictor system was unsuccessful because the underlying mechanical failure had already rendered the control linkage inoperative.