Evaluation of three helicopter preflight deicing techniques

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Procedures for preflight deicing of helicopters have not been refined nor standardized. Parked helicopters are often exposed to weather, allowing freezing precipitation and snow to accumulate on airframe and blade surfaces. Unless removed, snow and ice may linger after precipitation ends, grounding aircraft for hours to days, depending upon temperature. Newer helicopters with comlposite blades and fuselage components are susceptible to damage corn deicing operations because thermal and mechanical damage can cause delamination. In addition, glycol-based deicing fluids may cause corrosion of critical rotor head components. Therefore, there is a need to develop different ground deicing techniques for helicopters. This paper describes an experimental evaluation of the use of infrared radiation, hot water and hot air to deice helicopters before flight. The purpose of the experiment was to evaluate the effectiveness of each deicing method, and to assess the potential themial effects of each on rotor blade composites. Our greatest interest was the potential for using infrared radiation as a deicing agent, a technique that has been used to deice fixed-wing aircraft, but not helicopters. Introduction and Problem Hangared helicopters are protected from weather. However, helicopters exposed to ,weather during military, search and rescue, medevac, anld oil rig supply operations allow freezing precipitation and snow to accumulate on airhame and blade surfaces when parked. Adhering snow and ice may linger after a storm passes, grounding aircraft for hours to days, unless frozen precipitation is manually removed. Reports that manual deicing methods can require up to four hours to prepare a single aircraft for flight, and the inefficiency of manual methods, justifies the need for finding better methods. Modem helicopters are mor’e likely to be damaged by ice and snow removal techniques than are fixed-wing aircraft because large portions of rotor blades and fuselage surfaces are constructed of composites. Composites are susceptible to damage from physical impact, scraping, high temperatures, and rapid thermal cycling. In addition, glycol deicing fluids may corrode helicopter rotor heads and wash lubricants from bearings. This paper is declared a work of the U.S. Government and is not subject to copyright protection in the IJnited States. Boots and covers are occasionally used to protect helicopter components from ice and snow on the ground. For example, covers for blades, rotor heads, wind screens, tail rotors, engine inlets and, as on fixed-wing aircraft, pitot covers, are often used. However, reports of freezing of covers to aircraft surfaces make them less practical than desired. In addition, their use requires knowledge that freezing or frozen precipitation may occur when the aircraft is parked. Unless forecasts of freezing precipitation are very reliable and precipitation probabilities are high, aircraft are unlikely to be covered prior to a storm resulting in snow or ice-covered aircraft requiring deicing. This paper describes an experimental evaluation of the use of in&red radiation, hot liquid, and hot air to deice Army Blackhawk helicopters before flight. It also describes the utility of a portable ice imager system for use in deicing procedures. The purpose of the experiment was to identify deicing techniques available for helicopters, to select and evaluate the effectiveness of several methods, and to assess the potential thermal effects of each on rotor blade composites.