Vfrpilotpb,
The speed limits on a hulled boat are due to the fact that the bow wave created by the hull tends to grow longer as the boat speeds up, and when the wave reaches the stern, it adds to the wave from the stern. If you try to go faster, the wave gets deeper, but the boat goes almost exactly the same speed. In fact, the engine power starts making bigger waves, but the boat goes no faster. This is called the "Hull Speed" and is determined mostly by the hull length (the longer the faster).
Helos have something similar, because the rotor doesn't like being pulled thru the air at speeds much faster than about 170 knots. You can put bigger engines on, and get more payload, more lift, but probably little more speed.
The power required curve at high speed is actually a product of all the drags of the helo, but it is generally true that at Vmax, increasing power by 10% might only add 5 knots or so at 165 knots.
Last edited by NickLappos; 4th November 2004 at 19:35.