Garmin GDL 90 Installation Manual

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Appendix D – Construction and Validation of StructuresGDL 90 Installation Manual 560-1049-00 Rev B D-1APPENDIX D - CONSTRUCTION & VALIDATION OFSTRUCTURESThis appendix includes information necessary for testing load-carrying capabilities of equipmentmounting structures, such as shelves, mounting plates and mounting brackets, used to mount the GDL 90mounting tray.Baggage compartments and cabins or cockpit floors are good mounting platforms providing the floorattachments meet the strength requirements. If support racks, brackets or shelves need to be fabricated,they should be fabricated and attached to the aircraft structure in accordance with the methods outlined inAC 43.13-2A Chapter 2. After the structure is installed, it should be tested as outlined in AC43.13-2AChapter 1 to verify that it is capable of supporting the required loads.The GDL 90 installation must be capable of withstanding the Ultimate Load Factors listed in Table D-1for at least 3 seconds in each direction specified without damage or permanent deformation. Note thatthese required loads differ somewhat from those normally required for equipment installations.Since the combined weight of the GDL 90 and its equipment mounting rack is 6.4 lbs, the static loadswhich must be applied (Load Factor x 6.4 lbs.) will be the following:Direction of Force Load Factor Static Test Load(Load Factor x GDL 90 weight)Downward 6.6 g (6.6 x 6.4) = 42.24 lbsUpward 6.0 g (6.0 x 6.4) = 38.4 lbsSideward 4.5 g (4.5 x 6.4) = 28.8 lbsForward 18.0 g (18.0 x 6.4) = 115.2 lbsTable D-1. Static Test LoadOne method of determining the static load capability is as follows:1. Mark and drill the holes where the GDL 90 equipment rack will be mounted.2. Install four 8-32 machine screws (MS35206, AN526 or equivalent) in the four holes whichwill be used to mount the GDL 90 equipment rack using washers, nuts and nutplates to mount theequipment rack to the mounting surface. Note: some means of locking fastener must be used, ie.lock nuts & lock washers.2. For testing downward loading, place shot bags or other suitable weights totaling 42.24 poundswithin the footprint outlined by the four screw holes (assuming the mounting surface ishorizontal) or use a calibrated force gauge at the location of the center of gravity when the unit ismounted.3. Verify there is no damage or permanent deformation of the structure after 3 seconds.

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