Helpcpoter wing rotation rate?

Question

How many times per second do helicopter blades rotate, on average?

Answer 1

About 350-400 RPM.  The larger the rotor, the lower the RPM.

Answer 2

The rotation speed is dictated by the speed of the blade tip.  Because of compressibility factors as an airfoil approaches sonic, the effectiveness of that airfoil is reduced.  The designers try to keep the tip speed at around 450mph, so that as the helicopter nears its top speed, the advancing tip is still somewhat below the speed of sound.  In the case of a helicopter that can do 140 knots, that would put the advancing tip as it passes perpendicular to the airframe at just over 600mph, very near sonic at sea level.  this is one of the main factors that limits the forwarde airspeed of all helicopters.  You have to have the blades turning at a fast enough pace to provide the necessary lift, but keep them slow enough to allow for a decent airspeed.

A more specific answer, the 394rpm of an AStar rotor system is turning about 65 revs per second.

Consider the tail rotor, which is turning at just over 1300rpm, or the engine, which is turning over 40,000rpm