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A team from the USA rotorcraft industry, NASA, and academia was established to create a validated high-fidelity computational fluid dynamics (CFD) icing tool for rotorcraft. Previous work showed that an oscillating blade with a periodic variation in angle of attack causes changes in the accreted ice shape and this makes a significant change in the airfoil drag. Although there is extensive data for ice accumulation on a stationary airfoil section, high-quality icing-tunnel data on an oscillating airfoil is scarce for validating the rotorcraft icing problem. In response to this need, a two-dimensional (2D) oscillating airfoil icing test was recently performed in the Icing Research Tunnel at the NASA Glenn Research Center. Three leading-edge specimens for an existing 15-inch chord test apparatus were designed and instrumented to provide the necessary data for the CFD code validation.

Sikorsky Aircraft certificated the Model S-92A™ helicopter for flight in icing conditions in 2005. Since that time, the aircraft has flown in icing conditions throughout the world and the approval to launch a flight when icing conditions are forecast or reported has been valuable to operators. However, when the rotor ice protection system was inoperative due to a system failure, use of the aircraft on days of forecast icing was prohibited. Sikorsky Aircraft, therefore, elected to obtain certification of the S-92A helicopter to an EASA limited icing Special Condition so that UK and Norwegian operators in the North Sea sector could complete a mission when icing conditions were forecast, should the RIPS be inoperative on that day. A review of previously available icing data indicated that the S-92A helicopter could meet the requirements of the EASA Special Condition, but that additional flights were required to demonstrate full compliance.

An integrated approach for modeling the ice accretion and shedding of ice on helicopter rotors is presented. A modular framework is used that includes state of the art computational fluid dynamics, computational structural dynamics, rotor trim, ice accretion, and shedding tools. Results are presented for performance degradation due to icing, collection efficiency, surface temperature and water film properties associated with runback-refreeze phenomena, and shedding. Comparisons with other published simulations and test data are given.

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 VNE; 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.

PZL Mielec is in the process of certificating the ice protection systems installed on the M28 turboprop aircraft so that customers of that aircraft may operate in icing conditions. The M28 airplane is derived from the Antonov An-28, which was certificated in Russia to their icing certification requirements many decades ago. The M28 is equipped with a lot of western equipment, including Pratt and Whitney Canada engines and Hartzell propellers, and now has a no-hazard certification for the use of the installed ice protection system. The M28 ice protection equipment includes wing and tail anti-icing, engine inlet anti-icing, propeller deicing, and wing strut deicing. These systems have undergone a series of development flight tests and icing wind tunnel tests. This paper presents an overview of the flight tests and wind tunnel tests conducted to date.