Icing Scaling Laws Implemented in a Rotor Performance Degradation Model 2011-38-0082
The purpose of this paper is to describe the methodology to develop a simple model to assess performance degradation of the helicopter due to ice accretion on rotor blades (main and tail rotors).
The main idea is to use icing scaling laws and check their validity in the frame of performance. Therefore, as a first step, a review and a discussion are presented on icing scaling laws in order to compare simple parameters which describe several phenomena involved in the accretion process (water quantity, droplet trajectories, etc…) with available Eurocopter data. The second step is the identification of a global parameter which allows describing 2D airfoil drag degradation in a comprehensive way. In addition, an empirical law for 2D airfoil lift degradation and a criterion for natural ice shedding of blades are built in order to complete this modelling for helicopter rotors.
The 2D comprehensive laws, so developed and validated on several icing wind tunnel tests, are then implemented in an overall helicopter model (HOST) to provide an assessment of helicopter performance degradation for flight in natural icing conditions. Comparisons between model assessment and experimental results on several Eurocopter helicopters covering a large range of aircrafts demonstrate the accuracy and the confidence on the general model.