The goal of the Contrails project is to help preserve and disseminate the technical record of 20th century aerospace research, highlighting in particular the research endeavors of the Illinois Tech community.

Factor of Safety - USAF Design Practice

Report Number: AFFDL TR 78-8
Author: Miller, George E.
Author: Schmid, Clement J.
Corporate Author: Structural Integrity Branch
Laboratory: Air Force Flight Dynamics Laboratory
Date of Publication: 1978-04
Pages: 104
Contract: Laboratory Research - No Contract
Project: 2401
Task: 240101
AD Number: ADA070237

A review of the historical development of the 1.5 structural factor of safety for airplanes, the 1.4 factor for manned space vehicles, and the 1.25 factor for missiles is presented from an Air Force perspective. Several variations and experimental applications of the factor of safety design concept and reliability based design concepts are also reviewed to show their interaction. Although not without criticism, the factor of safety design concept has become an almost universally accepted measure of flight safety. There is, however, a tendency among engineers to both challenge the continued application of factors of safety for efficient airframe design, and yet to avoid any changes that would challenge the confidence of future designs. The use of reliability based concepts will probably increase but their application to airframe design may be limited. The factor of safety still covers many contingencies and it appears at this time there will be a continuing need for some factor.

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