Laboratory and field investigations following helicopter accidents. Includes statistics on survivability with different models of helmets such as the HGU-56. Impact rate of UH-60 (Black Hawk) helicopter, CH-47 (Chinook) helicopter, UH-1 (Huey) helicopter, OH-58 (Kiowa) helicopter, and AH-1 (Cobra) helicopter. Factors used for equipment design are addressed.