The Development of an Advanced Anti-Icing/Deicing Capability for U.S. Army Helicopters. Volume 1. Design Criteria and Technology Considerations

Representative values of icing-related variables aloft in freezing rain and freezing drizzle

“…In an attempt to develop design values for U.S. Army helicopters, a 1975 report [23] drew on the hourly rain rate statistics of reference 1 to find the extreme (99 percent) limit for RWC in ZR conditions. Simple equations borrowed from radar meteorology were used to convert extreme ZR rain rates to corresponding values of RWC and effective dropsize.…”

“…One reference [23] points out that the precise size of ZR droplets is really of minor importance, because the large droplet sizes involved ensure collection efficiencies near 100 percent anyway.…”

A Hybrid De-icing Strategy Utilizing Tailored Anti-Icing Coatings Paired with Electro-Thermal and Electro-Mechanical Ice Protection Systems for Use on Rotary-Wing Aircraft

“…Electro-thermal de-icing systems are heavy and require large power supplies. Typically, not all blades can be de-iced at once, due to the high power demand [75]. This allows additional ice to form when the system is not in use.…”

“…For the system to be useful for longer durations, more fluid must be carried, hence increasing the weight. Fluid-based systems cannot be used for military helicopters due to the risk of punctures to the reservoir lines from enemy fire during battle [75].…”

“…Similar to a bleed air de-icing system on fixed-wing aircraft, heated air can be captured from the engine and circulated in the rotor blades. Another configuration uses heaters to warm the air prior to circulation [75]. These systems can provide good protection and are fairly lightweight; however, they entail several disadvantages.…”