Ground taxi and automated control systems

[nickel]

Hi,

I am working on a simulation model and have a problem with taxi. I am trying to model a helicopter which is steered with differential braking. The helicopter also has an AFCS system with heading hold capability.

Now the problem is, when taxiing on the ground, AFCS tries to keep the heading constant. So, tail rotor opposes the differential brakes, an the heli is not maneuvrable at all!

Obviously, heading hold must be off on the ground. On the other hand, we would like to turn it on during take-off. Now the question is how is the transition made in real helicopters? Are there sensors on the landing wheels that turn on/off heading hold?


Thanks in advance