What happened
On April 28, 2001, a Bell 206 Jet Ranger helicopter, registration OO-KBM, was performing sightseeing flights over a cycling event near Maastricht. The aircraft was operating from a field located just across the Belgian border. During the second flight of the day, the pilot attempted a hover taxi at an altitude of approximately one meter, intending to reposition the aircraft to face into the wind before takeoff.
While attempting to turn the nose into the wind, the pilot experienced vibrations throughout the aircraft and felt the cyclic control stick become blocked in the aft position. In response to this sensation, the pilot attempted to land the helicopter. During this maneuver, one of the skids struck the ground, causing the helicopter to bounce and eventually tip onto its right side. All four passengers and the pilot were able to exit the aircraft unassisted, though the helicopter was heavered damaged.
The investigation
Investigators examined the mechanical state of the aircraft and the environmental conditions at the time of the accident. Technical inspections revealed no mechanical failures or deficiencies in the helicopter's systems. The weather conditions were found to be within the legal requirements for Visual Flight Rules (VFR) operations.
Findings
- The investigation identified turbulent airflow as a likely source of the vibrations, specifically caused by the tail rotor's wake being blown into the main rotor disk by a strong tailwind.
- To maintain a zero ground speed against a strong tailwind, the pilot had to apply significant aft cyclic input, which likely reached the physical limit of the control's travel.
- A combination of factors—including a forward center of gravity, a high takeoff weight, strong tailwinds, and a low hover altitude—may have caused a rapid demand for increased power.
- The pilot's failure to immediately and adequately compensate for this power demand likely led to a loss of altitude.
- The pilot's limited experience on this specific aircraft type may have contributed to the inability to manage the sudden change in flight dynamics.
Safety action
- The investigation noted that during operations with strong tailwinds, it is standard practice to perform hover taxis at a higher altitude than the standard one-meter level to provide a safety margin.