Originally Posted by rotorfossil
I suspect that the answer may be that the higher weight requires a higher lever setting and therefore higher angle of attack to maintain to maintain the same Nr. This moves the L/D of the whole rotor disc towards its optimum conditions. The same reason that max range in autorotation is achieved generally at the lower end of the RPM band.
I suspect you're right. Certainly sounds plausible.
Originally Posted by Tourist
Does anybody here really believe that if you added a million tons to a helicopter it would fall more slowly?
Or conversely, if you attached an enormous helium balloon to the rotor head we would plummet in auto?
No, our internal newtonian physics professor can spot a flawed theory quite well.
A extremely heavy helicopter would fall like a brick with very high RRPM that can't be controlled, because not enough collective is available / the rotor would stall due to excessive AOA.
(However, it is easy to imagine that this heavy helicopter would still be able to autorotate if the rotor was made large enough. A 1:12 scale RC helicopter can autorotate, and so can a CH-53.)
A extremely light helicopter - forget the helium balloon though, that is not the same thing - would fall like a brick because insufficient energy is available to keep the rotor turning.
(However, if the rotor was small enough, it would produce less drag and still be able to autorotate. Think maple seed vs. chinook)
The question is, what happens in between, and why.