Retreating Blade Stall
From the manual.
The Comanche is rated at a top red-line speed of 175 knots. Although it is possible to exceed this maximum safe operating speed, the manufacturer (and the Army) would prefer that you don't.
As you near this maximum speed, you'll automatically trigger a Receding Blade Stall warning. This warning takes the form of a flashing red groundspeed indicator, voice and audible alarm.
Once you exceed 175 knots, the Comanche will become unresponsive and nose over due to this receding blade stall phenomenon. Eventually, if you do not slow down, your helicopter will depart controlled flight (DCF) and crash. To prevent this from happening, slow down to within safe operating speed tolerances (175 knots). Control will be returned to you at this time.❞