MIL-STD-209K APPENDIX D
the overall cost impact based on sound risk/benefit analysis. Bypassing the submission of analysis, and performing a test to prove structural adequacy, may require additional local structural testing or analysis to adequately substantiate the back-up structure and deter- mine locations of high stress. Positive margins of safety for limit and ultimate load condi- tions are required for all structure.
D.3.6 Structural Analysis.
Structural analysis consists of structural substantiation of the vehicle, tiedown provi- sions and backup structure for the load factors defined in paragraph D.3.1 As part of a preliminary structural analysis package, a matrix of all possible tiedown patterns, cone of action for each vehicle tiedown, and plans to structurally substantiate the individual tiedown patterns and cones of action shall be submitted to NAVAIR for approval. The analysis package shall show structural substantiation by structural testing, analysis or both, for securing the vehicle to the aircraft. The analysis shall include structural substantiation of the vehicle, vehicle backup structure, and provision. Methods of structural analysis and sub- stantiation include hand analysis, finite element analysis and structural test. All high stress structural members and critical load cases shall be identified, margin of safety calculations shown, location of high stress in the model illustrated, assumption stated for boundary conditions and interpretation of results, and enough information in the vendor submitted structural report such that an analyst can reproduce the results from the information pro- vided. Load paths shall be identified for each provision with structural analysis showing positive margin of safety or passage of structural testing. All analysis shall be performed to structurally substantiate the local tiedown provision and backup structure to the point where nominal uniform stress occurs. When multiple provisions use the same back up structure the worst loading case scenarios shall be assumed, identified and analyzed. Standard structural analysis techniques shall be applied, such as stress reduction factors for welds, detailed finite element analysis identifying local high stress areas, conservative assump- tions for load application and load distribution, etc. Margins of safety shall be positive for all ultimate load cases as defined in paragraph D.3.1. Positive margins of safety for limit and ultimate load conditions are required for all structure. Limit load cases shall show no per- manent set by analysis or test. A structural analysis report shall be submitted for approval
to the transport approving agent.
D.3.6.5 Vehicle Structural Analysis and Test.
The entire vehicle shall be structurally substantiated for carriage in Navy/Marine Corps aircraft by test and/or structural analysis. The vehicle structure and all peripheral components shall remain undeformed and an integrated unit when subject to the limit load conditions specified in paragraph D.3.1. The vehicle subject to ultimate load condi- tions can deform, but must remain as an integral unit. Structural substantiation can be shown by test, structural analysis by hand or finite element, engineering inference or a combination of methods. The vehicle and all peripheral components, such as cargo, weapon systems, seats, mirrors, windshield, seats etc., shall be shown to be retained and undeformed for the appropriate condition in paragraph D.3.1. A test plan or struc- tural analysis shall be submitted for approval to the approving air transport certifying authority. Testing may be static or dynamic in nature or a combination of both. For ex-
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