Rotor blade shed ice projectile length prediction

Ice shed from rotor blades can be a ballistic concern for rotorcraft. These ice projectiles could damage the empennage and tail rotor of a conventional helicopter, or the fuselage of a tilt rotor. This paper presents research conducted to predict the ice projectile length of shed ice leaving the tip of a rotating blade due to the triggering of an electro-thermal deicing system. Neglecting rigid and elastic blade motions, an Euler-Bernoulli beam bending model was developed to predict the length of shed ice as it leaves the tip of the rotor blade. The model was able to predict the ice projectile length within 11% using experimentally measured ice shapes and within 18% using LEWICE-generated ice shapes. Owing to a large discrepancy in reported values found in the literature, the ultimate tensile strength of the impact ice was measured experimentally and found to be 0.685 MPa with a standard deviation of 38%.