The glide ratio for an S-76 is about 4.2, at min rate of descent and maybe 4.7 at best glide.
The lowest rate of descent in the glide is driven by the power required to fly at best rate of climb speed, since the engine is no longer the power source, the power is taken from the potential energy of the helicopter - its altitude. Lowest rate of descent is at or close to Vy (best rate of climb) but might read differently on the airspeed indicator due to calibration differences between the steep descent of auto and the steep climb of a max climb rate. In other words, the airspeed might READ differently in auto, but most likely the actual airspeed is the same as a climb.
Similarly, the best angle of descent is close to the best range speed, for the same reason. Best range is where the fuel burned takes you the farthest. If you substitute fuel burned for altitude lost (same thing, really - energy consumed is energy consumed) then best glide is farthest flown for a unit of descent.
The steep glide angle relative to an airplane is due to the basic inefficiency of the rotor as compared to a wing. Most airplanes have a glide ratios of 8 to 12 to 1, and sleek airplanes can be 18:1. Gliders can be impossibly efficient, with 40:1 in the world class ones.
Rotors are less efficient than wings onlu until the winged machine tries to hover, that is.........
Last edited by NickLappos; 12th Jul 2013 at 17:44.