AW139 Full Ice Protection System flight testing with US Army Helicopter Icing Spray System

The use of the US Army’s Helicopter Icing Spray System (HISS) is a powerful tool for the development of an ice protection system, and the results can be useful to support civil certification activities. The HISS is a CH-47D helicopter attached with a spray bar system generating a stabilized cloud of artificial ice for prolonged periods: the helicopter under test can remain in the cloud to build up even heavy ice accretions on unprotected components or to verify the performance of protected components at fixed design points. AgustaWestland (AW) in cooperation with the US Army’s Aviation Technical Test Center (ATTC) used the HISS for the in-flight development of the AW139 Full Ice Protection System (FIPS), which can be used to support the application for civil certification presented to EASA, FAA and DOT Canada authorities. AW139 performed a first HISS campaign in February-March 2007, testing the “cold blades” configuration (i.e. without ice protection for main and tail rotors, only for windshields and engine intakes) in order to verify the basic helicopter performance in ice and to assess its behaviour in case of failure of the rotors protection system. A second HISS campaign was performed by AW139 in February-April 2008 to test the complete system also with rotors protection. The use of the HISS for AW139 FIPS testing before the start of the full scale flights in natural icing allowed simulated failure modes to be evaluated in a safe environment and even early discovery of needed refinements in the system. The HISS tests allow helicopter immersion in a stabilized cloud for prolonged times, and the flights output can be compared with the results obtained with analysis and wind/ice tunnel tests, to optimize these simulation tools. Additionally the HISS results can be used, especially for the corner points of the OAT/LWC/MVD envelope defined by civil certification, as support and validation of the results obtained in natural ice flights.