206L Vertical Hops on Lightly Loaded Aircraft

Van Horn Aviation has recently become aware of a particular flight condition that can set off an extreme vertical hop on lightly loaded LongRangers using VHA main rotor blades.

In cases where a 206L fitted with VHA main rotor blades is operating light—for example, with only a single pilot on board, less than a full tank of fuel and no cargo—the helicopter can experience a severe vertical hop in turbulent conditions. When initiated by a gust at high speed, this very light aircraft configuration can allow an interaction to occur between the rotor blades and the nodal beam mount. The resulting vertical hop can become very uncomfortable. This seems to be an unusual situation, but if the helicopter gets into this condition the appropriate action is to load the rotor by banking. By loading the disk, the frequency of the system is quickly changed, thereby resolving the issue. 

Please pass this along to your pilots and operations crew. If you have any questions, please contact us.