Comparative Vertical Impact Testing of the F/FB-111 Crew Restraint System and a Proposed Modification.

Abstract : An impact test program was conducted to evaluate the operational F/FB-111 crew seat and restraint system and a proposed modification. A primary objective of the program was to compare human response to vertical impacts in the two restraint harnessess. A total of 67 human impact tests were performed on the Vertical Deceleration Tower up to 10 G peak, 26 ft/sec. Subjects were exposed to comparable impacts at different seat elevations in both harnesses to allow parametric analysis of the test results. Measured data included seat acceleration and velocity, head and chest translational acceleration components, triaxial forces acting on the seat and footrest, forces acting at the restraint harness, attachment, and deplacements of various body segments. The resultant head and chest accelerations were significantly greater in the modified harness than in the operational harness, regardless of seat elevation. On the basis of this comparison, the proposed modification to the F/FB-111 crew seat and restraint is not recommended for implementation. Future restraint harness modification proposals should be based on careful evaluation of all unconventional design features of the operational harness and should address all mechanisms by which adverse loads may be imposed on the seat occupant. In addition, future redesign efforts of the F/FB-111 escape system should provide improved landing impact attenuation.