The tip of a helicoptor rotor blade can reach speeds of roughly 300 mph (130 m/s). It takes about 30 seconds to get them up to speed and they have a typical radius of 20 feet (6 m). What is the average angular acceleration of the rotor blades as they get up to speed?

a = (Vf - Vo) / t,

a = (130 - 0) / 30 = 4.33m/s^2, Linear.

C = 3.14*D = 3.14 * 2*6 = 37.68m/rev.

a = 4.33m/s^2 * (6.28/37.68)rad/m,
a = 0.722rad/s^2.