The diameters of the main rotor and tail rotor of a single-engine helicopter are
ID: 1430461 • Letter: T
Question
The diameters of the main rotor and tail rotor of a single-engine helicopter are 7.55 m and 1.02 m, respectively. The respective rotational speeds are 458 rev/min and 4,129 rev/min. Calculate the speeds of the tips of both rotors. main rotor m/s tail rotor m/sCompare these speeds with the speed of sound, 343 m/s. vmain rotor / vsound = vtail rotor / vsound = The diameters of the main rotor and tail rotor of a single-engine helicopter are 7.55 m and 1.02 m, respectively. The respective rotational speeds are 458 rev/min and 4,129 rev/min. Calculate the speeds of the tips of both rotors. main rotor m/s tail rotor m/s
Compare these speeds with the speed of sound, 343 m/s. vmain rotor / vsound = vtail rotor / vsound = main rotor m/s tail rotor m/s
Explanation / Answer
Given
main rotor and tail rotor diameters are d1 = 7.55 m, d2 = 1.02 m
their radii r1 = 3.775 m, r2 = 0.51 m
rotational speeds W1 = 458 rev/min = 458/60 = 7.63 rev/s = 47.75 rad/s
and for tail rotor W2 = 4129 rev/min = 68.82 rev/s = 432.40 rad/s
and for speed V = r*w ==> V1 = r1*W1 = 3.775*47.75= 180.26 m/s, vmain rotor / v sound = 180.26/330 = 0.55
for tail rotor speed V2 = r2*W2 = 0.51*432.40 = 220.524 m/s , Vtail rotor / v sound = 220.524/330 = 0.67