The helicommand is Laser and gyro controlled. When the lasers cannot see the ground (weak lasers) the gyros take over.

The Co-pilot FS8 or CPD4 works on IR energy. The ground is hotter than the sky principle. That IR energy varias slightly as you go up in altitude.

I have seen both fly on helicopters and own an FS8 installed in a plank. They both have their ups and downs.

The Co-pilot systems can be fooled by a hot engine or exhaust. A friend of mine installed one on a gas powered AP Helicopter and he told me that the heat of the engine made the co-pilot read a false signature and made the helicopter tilt away from the heat source. The heat was in front of the sensor, so the helicopter was always backing up.

The Helicommand, is inmune to heat signatures and the system is calibrated by the ground sensors while the heli is on the ground. When the ground sensors cannot detect the ground anymore, the unit switches to gyro-stabilized flight. I do not know much more about this unit. Other than the guy that had the heat problem with his Co-pilot system changed to a helicommand.

Either system seems to do it's intended job. Would I recommend them? Probably not. I do have my FS8 on a plank to teach newcomers the down and dirty basics of flight without jeopardizing my model. On a helicopter, they could be a great tool or a hindering technology, depending on what point of view you take. I believe that is the point of view Barracuda and Vince have but they were not so eloquent.

Rafael