1.1 PROBLEMnThe operation of helicopters on unprepared sites has proved to be a problem because of the ground erosion created by the rotor downwash. When hovering at low altitude over dry sand or loose dirt, helicopters pilots usually find themselves flying blindly in a dust cloud. Operations in sandy environment have shown that sand ingested by the engines and the action of the flying particles on the rotor greatly reduce the life of engine and rotor components. Such operations generate dust clouds during landing and takeoffs which reveal the presence and location of the aircraft to the enemy.n1.2.1 PHASE I ANALYSES AND MATERIALS INVESTIGATIONnA review of potential materials was performed. An in-house material review and an industry-wide search for potential materials were conducted to ensure that the latest material development was reflected in the study.n1.2.2 PHASE II CONCEPTS INVESTIGATIONSnCombinations of materials and application concepts were investigated. Single-component materials as well as systems comprised of multiple elements were evaluated.n1.2.3 PHASE III LABORATORY TESTINGnA laboratory testing program was conducted to efficiently screen a large number of materials. Cure rate and strength under adverse tempera¬ture and/or moisture conditions were the most significant characteristics under evaluation during this phase. Samples of materials exhibiting the best potential were prepared for wheel load testing.
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