you dont need to repeat youself in every post, things that were leant at heli school. of caurse the pressure never increases if you want to hold a hight above the ground, as the pilot keeps the pressure constant with the collective. did you even think about what i said on the power chart? it indicates how much pressure you could put under the helicopter at a particular speed (power available). it distinctly shows slightly less power at hover than a couple of knots. this is the cushion im talking about. your right, the pressure doesnt actualy rise, because the pilot reduces the collective to save it. the saved pressure now shows on the performance chart.
so for you nick, i wont call it ground cushion anymore. its now, THE CONSERVATION OF POTENTIAL GROUND PRESSURE!
DAVE
thrust REQUIRED is constant.
turbine engines also suffer at altitude, air is less dence. but on RPT jets the engine is designed to operate at a particular altitude so flying below or above this hight the engine is inefficient.