Vertiflite May/June 2021

Grover E. Bell Award, given for outstanding research and experimentation that has been brought to fruition. Enrico Bellussi, head of Leonardo’s Ice Protection Project since 2004, has supported the certification of the AW139, AW189 and now AW169 ice protection programs. He noted that “Full ice protection means maximum protection. The helicopter can enter all ice conditions with no limitations, except in the case of Supercooled Large Drops (SLD)” — that is, when droplets have a diameter over 50 microns (0.002 inches or 0.05 mm). According to Leonardo, the FIPS system is available as an option, and includes ice detectors, an automatic activation system with a manual back-up, electrical power generators, engine intakes protection grids, a heated windshield and heated main and tail rotor blades. The AW139 has two dedicated generators — one of 45 kW and 25 kW for the other — for a total of 70 kW altogether. The AW189 has only one dedicated generator (30 kW) with the 25 kW auxiliary power unit (APU) generator as a back-up; the power supply for the heated windshield comes from the basic generators. The AW169 has two dedicated generators of 30 kW each.

Pre-production AW189 “P6” painted in Era Helicopter colors at Heli-Expo 2014 in Anaheim, California.

HISS deicing trials between the JCH-47D Chinook and AW189 in Michigan. (Leonardo)

Leonardo’s Limited Ice Protection System (LIPS) includes ice detectors, an SLD marker, an ice accretion meter, heated engine inlets and a heated windshield. LIPS permits flight within a known and defined envelope of icing conditions, provided that the capability to descend into a known band of positive temperature is available throughout the intended route, typical of conditions encountered, for example, over the North Sea. FIPS adds electrically heated main and tail rotor blades, which consume additional power and add weight to the aircraft, but allows the rotorcraft to operate in forecast icing conditions. FIPS, therefore, expands the helicopter’s operational flexibility by providing real all- weather capability, as required in a growing number of applications, including offshore, search and rescue/emergency medical service, corporate transport and shuttle service. Typically, rotor blade deicing systems use electrical heating blankets built into the leading edges. The electricity from the generator is transmitted through slip rings on the rotor hub. Both LIPS and FIPS are available as options and keep performance and procedures unchanged for Category A operations (meaning the flight can continue to safety evenwith one engine inoperative). They also do not generate any restrictions during instrument flight rules (IFR) operations. HISSing Over the Great Lakes The Helicopter Icing Spray System (HISS) is an important asset that covers one aspect of rotorcraft civil certification for helicopter ice protection.

The Leonardo HISS trials have been carried out over many years above the US Great Lakes region by the US Redstone Test Center’s (RTC) Aviation Flight Test Directorate (see “Testers to Order,” Vertiflite , Sept/Oct 2013). The AFTD detachment — flying from Duluth, Minnesota, until 2014 and from Marquette, Michigan, since then — includes a Boeing JCH-47D Chinook with a 1,800- gal (6,800-liter) tank that sprays water drops onto the customer’s aircraft to simulate natural icing. The tests are conducted with a spray boom fitted onto the JCH-47D; a Beechcraft C-12D chase aircraft accompanies and escorts both helicopters, filming the tests, as well as conducting initial ice sampling, monitoring, etc. In each airframe campaign, there are several stages that must be passed in order to support certification: first the definition of the HISS test matrix; then a full assessment of the test results; validation of the results; and, finally, presenting the HISS test results to the certification board. The parameters for this type of flight test include the ice cloud generated by the 36-by-8-ft (11-by-2.4-m) HISS spray bars, a test duration of 30–45 minutes, a medium value diameter (MVD) of less than 70 microns (0.0028 inches or 0.07 mm) and a liquid water content (LWC) that is typically less than 0.001 oz/ft³ (1 g/m³). The HISS test matrix has a number of definitions and benchmarks, ranging from initial performance checks and debugging the system, looking at continuous maximum icing (CMI) and intermittent maximum icing (IMI) corner points, and SLD checks. Simulated failure tests are also performed, including partial and total heating loss on both main rotors and tail rotor. HISS tests alone are not enough to ensure certification,

May / June 2021

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