Garmin GTX 33 Installation Manual - Page 51

APPENDIX A CONSTRUCTION AND VALIDATION OF STRUCTURES A.1 Static Test Loading This appendix includes information necessary for testing load-carrying capabilities of equipment mounting structures, such as shelves, mounting plates and mounting brackets, used to mount the GTX 33 remote mounting tray. Baggage compartments and cabins or cockpit floors are good mounting platforms providing the floor attachments 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 in AC 43.13-2B Chapter 2. After the structure is installed, it should be tested as outlined in AC 43.13-2B Chapter 1 to verify that it is capable of supporting the required loads. The GTX 33 installation must be capable of withstanding the Ultimate Load Factors listed in Table A-1 for at least 3 seconds in each direction specified without damage or permanent deformation. Note that these required loads differ somewhat from those normally required for equipment installations. Since the combined weight of the GTX 33 and its equipment mounting rack and connector is 4.3 lbs, the static loads which must be applied (Load Factor x 4.3 lbs.) will be as follows: Table A-1. Static Test Load Direction of Force DOWNWARD UPWARD SIDEWAYS FORWARD Load Factor 6.6 G 6.0 G 4.5 G 18.0 G Static Test Load (Load Factor x GTX 33 weight) (6.6 x 4.3) = 28.4 lbs (6.0 x 4.3) = 25.8 lbs (4.5 x 4.3) = 19.4 lbs (18.0 x 4.3) = 77.4 lbs A.2 Determining Static Load Capability A recommended method of determining the static load capability is as follows: 1. Mark and drill the holes where the GTX 33 equipment rack will be mounted. 2. Install four 8-32 machine screws (MS35206, AN526 or other approved fastener) in the four holes which will be used to mount the GTX 33 equipment rack using washers, nuts and nutplates to mount the equipment rack to the mounting surface. Note that some means of locking fastener must be used, e.g. either lock nuts or steel nuts with lock washers. 3. For testing downward loading, place shot bags or other suitable weights totaling 28.4 pounds within the footprint outlined by the four screw holes (assuming the mounting surface is horizontal) or use a calibrated force gauge at the location of the center of gravity when the unit is mounted. 4. Verify there is no damage or permanent deformation of the structure after 3 seconds. 5. Fasten a 36 inch loop of suitable material such as fishing line, braided wire, or other similar material having a breaking strength of at least 100 lbs., diagonally between two of the screws. Then fasten another loop diagonally between the other two screws, adjusting the length of the loop so it exactly matches the first. 190-00906-00 Rev. F GTX 33 Installation Manual Page A-1