S-76D™ Tail Rotor Ice Impact Test

This paper presents the test method and results from ice impact testing conducted on representative S-76D™ Helicopter Tail Rotor (TR) blade and TR control system assemblies. Full scale ice impact tests on the leading edge of the tail rotor blade paddle, pitch links, and a pitch beam were conducted to demonstrate sufficient residual strength for continued safe operation following a potential ice strike. During testing the tail rotor system remained stationary with centrifugal force (CF) simulated by stiffening the tail rotor blade with spring loading at the bolted joint. The ice pieces were shot at the blade/control specimen at an equivalent forward velocity of ice shedding from an aircraft traveling at 155 knots (1.0 V_NE; 261.61 ft/s) plus an equivalent forward velocity of the blade given the rotational velocity at the tip (670 ft/s @ 99.4% TR Nr). Additional shots were conducted to define the relationship between impact energy and projectile fracture mode. The TR blade orientation was approximately at 0° collective pitch at the bolted joint, which demonstrates the greatest potential damage configuration possible in current facility. Ice specimens impacted on the blade were incremented in size in order to establish a blade damage/ice shed size relationship. The S-76D Tail Rotor system demonstrated an ice impact resistance of up to and including 1.05 lb equivalent impact energy with no detectable structural damage. Inspections and posttest analysis have confirmed that the control system and the tail rotor blade can withstand the impact of a 1.05 lb ice projectile shed from an A/C travelling at V_NE and sustain only minor, non-structural damage.