The limited space between crew seats and controls, dashboards, or outside objects with which the crew can collide is also a container problem. The thoughtful investigator will evaluate the living space remaining after impact forces have been dissipated, remembering that some ductile metals can rebound after they have compromised volume, leaving few traces of their brief invasion into the aircrew compartment. The Restraint System . To secure an aircrewman with a system of straps designed to withstand a 10,000 pound load is futile unless the system is maintained and used properly. Worn or damaged straps may fail at reduced loading.
Unused restraints speak for themselves.
Loosely secured restraints present a special problem because of dynamic overshoot. This occurs when the aircraft has begun deceleration over time before the crewman actually impinges on his straps, which may either fail or rebound. Crash force calculations under the latter circumstances will be in error by at least a factor of two. Loose restraints invite submarining in which the aircrewman can exit the seat in whole or in part without unfastening the restraint buckle. Buckles that open under survivable deceleration forces or that cannot be opened with one hand must be identified.