Create trigger with the following in the 'on action'
heli setHitPointDamage ["HitVrotor, 1"];
And then set the trigger on eihter a radio or activated by the faction's heli being tested.
Place a helicopter and name it 'heli'
Set to flying.
Either fly through the trigger or activate the trigger via radio when going +150kph
Once the rotor fails, shut off the engine via the action menu.
Proceeded to autorotate to a area of land.
Note as your airspeed drops the helo will begin to lean right and finally spin quickly when at -50kph just before landing.