Basic Principles of Crashworthiness

Crashworthiness can be defined as the ability of an aircraft and its internal systems to protect occupants from injury in the event of a crash. In general, injury in aircraft crashes can be considered to arise from three distinct sources: (1) excessive acceleration forces; (2) direct trauma from contact with injurious surfaces, and; (3) exposure to environmental factors such as fire, smoke, water, and chemicals resulting in bums, drowning or asphyxiation. Consequently, effective crashworthiness designs must consider all possible sources of injury and eliminate or mitigate as many as practical for a given design impact limit. This involves considerations of (1) strength of the container (cockpit and cabin), (2) adequacy of seats and restraint systems, (3) adequacy of energy attenuation systems, (4) injurious objects in the local environment of occupants, and (5) post-crash factors, principally fire prevention and adequacy of escape routes. The U.S. Army UH-60 Black Hawk and AH-64 Apache helicopters were the first helicopters built to modem crashworthiness specifications. This paper uses investigations of crashes of these helicopters to illustrate basic crashworthiness principles and to demonstrate their effectiveness when systematically incorporated into helicopter designs.