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Helicopters

There is no flying object being more fascinating than helicopters:

• They do not only fly but are able to hover above a point, fly to the side and even backwards.
• The aerodynamics around the blades is extremely complex:
  • The flow velocity at the balde tips is near at the speed of sound, whereas during the foreward flight there are regions at the rotor disc where there is a reverse flow around the blades.
  • The blades do not move through undisturbed air such as the wings of planes, but move through the vortex sheets of the preceeding blades.
  • During the upward vertical flight, the helicopter has to climb in its own downwash, whereas in the downward flight, the helicoter is likely to fly in the so called vortex ring state.
• The torque generated by the main rotor has to be balanced by the thrust of the tail rotor
• And much more ...

Model Helicopters

Even more fascinating are model helicopters since they can fly maneuvers which are far beyond the possibilities of the full scale helicopters The can fly inverted and can be controlled in such way that they seem to stand vertically in the air. During the pitch changes the air is accelerated to and fro through the rotor disk.

Simulation

The simulation of the described behavior is an interesting and chalanging task. Not only the forces and the torque of the rotors have to be calculated, but also the dynamics of the air has to be considered. These are topics which are beyond typical publications concerning the aerodynamis of full-scale helicopters. These publications deal with stationary states, where for the model helicopters dynamic processes are more important. This is the setting of the simulation program HELI-X. Have fun with this web pages and - of course - with HELI-X.