Amt 611 Covering, Finishes, and Wood Structures PDF

AMT 611 COVERING, FINISHES AND WOOD STRUCTURES 1 AMT 611 COVERING, FINISHES AND WOOD STRUCTURES AIRCRAFT COVERINGS 2 PART 1 COVERING Fabric-covered aircraft, like the Wright Flyer, were important in early aviation due...

AMT 611 COVERING, FINISHES AND WOOD STRUCTURES 1 AMT 611 COVERING, FINISHES AND WOOD STRUCTURES AIRCRAFT COVERINGS 2 PART 1 COVERING Fabric-covered aircraft, like the Wright Flyer, were important in early aviation due to their light weight. However, fabric coverings are flammable and less durable. Advantage: light weight Disadvantages: flammability and lack of durability. Early aircraft used fabrics like linen and cotton, but these sagged. Oils and varnishes helped. It made the fabric tight and smooth but was very flammable 3 COVERING Aircraft fabrics like cotton had a short lifespan and were replaced by aluminum, which was more durable and fire- resistant, revolutionizing aviation with its use in engines, frames, and coverings. While aluminum and composites are now common, fabric still covers gliders and light aircraft. 4 Fabric Term 5 Fabric Term  Warp—the direction along the length of fabric.  Fill or weave—the direction across the width of the fabric.  Bias—a cut, fold, or seam made diagonally to the warp or fill threads.  Pinked edge—an edge which has been cut by machine.  Selvage edge—the edge of cloth, tape, or webbing woven to prevent raveling. 6 Cross Coat 7 Approved Materials The FAA must approve all materials used in aircraft fabric covering and repair, including fabric, tapes, and coatings, to ensure safety and compliance with regulations.  Fabric A Technical Standard Order (TSO) is a minimum performance standard issued by the FAA for specified materials, parts, instruction or a STC. Types of Fabric:  polyester  Dacron  Stits  Ceconite  Poly-Fiber  Superflite  Oratex 8 Approved Materials fabric can be overlapped differently on high wing and low wing aircraft. 9 Approved Materials  Anti-Chafe Tape - Anti-chafe tape protects fabric from sharp edges. This self-adhesive cloth tape is applied before the fabric, after cleaning and priming the aircraft. 10 Approved Materials  Reinforcing Tape - is most commonly used on rib caps after the fabric covering is installed to protect and strengthen the area for attaching the fabric to the ribs. 11 Approved Materials  Rib Bracing - Rib bracing tape secures wing ribs in place during the fabric covering process. It's applied in an alternating pattern across the rib caps. 12 Approved Materials  Surface Tape - usually polyester, is applied after the fabric to cover seams and edges. It comes in various widths and styles, including bias cut for curves 13 Approved Materials Grommets - reinforce drain holes in fabric. They are glued in place, then a hole is made in the fabric. Some grommets have shields to prevent water from entering. 14 Inspection Rings - Inspection rings are attached to the fabric to allow for inspection of the underlying structure. 15 16 Products and procedures specified in the applicable to complete an airworthy fabric re-covering job. Primer – a base coat used to help treat a surface before applying a topcoat. Before covering, the aircraft structure must be cleaned, inspected, and primed with a compatible treatment. Use the primer specified by the manufacturer. Fabric Cement - a special cement, which must be compatible with the primer and sealer 17 Products and procedures specified in the applicable to complete an airworthy fabric re-covering job. Fabric Sealer - protects the fabric and provides adhesion. It's applied after the fabric is attached and shrunk. Use a sealer to avoid damaging the airframe. Fillers - After sealing, a UV-blocking filler is sprayed onto the fabric. This is crucial to protect the fabric from the sun. Fillers may be dope- based or proprietary formulas Topcoats - After the fabric is installed and protected, topcoats provide the final appearance. Use the specified topcoat and procedures for an airworthy finish 18 Different Additives Additives are often used with fabric coatings. Only approved products listed can be used; substitutions are not allowed Catalysts suppress the inhibitors and initiate the curing process Starts a reaction that allows the chemistry to evolve to a cured solid form. Thinner is a solvent that adjusts a product's consistency for application. 19 Different Additives Retarder slows the drying time of coatings, allowing a smoother, glossier finish. It's used in hot conditions or to prevent blushing in high humidity Accelerator speeds up drying time, especially in cold conditions or to avoid contamination. 20 Different Additives Rejuvenator softens coatings. It's used on dope finishes only. Fungicide additives are not typically needed for modern polyester fabric coverings, as the coatings often have anti-fungal agents. 21 Fabric Strength Aircraft fabric must maintain at least 70% of its original strength. Strength is checked at every 100-hour and annual inspection. 22 Fabric Testing Devices Mechanical fabric testers that press or pierce fabric are not FAA- approved. Mechanics use them at their discretion to get a general idea of fabric condition. Accuracy varies depending on the device, coating thickness, and fabric type. If results show low strength or the fabric looks bad, more accurate testing is Maule punch tester needed. 23 Fabric Testing Devices Maule punch tester 24  General Fabric Covering Process Removal of Old Fabric Coverings To start re-covering, carefully cut away the old fabric. If you need to use it as a template for marking inspection panels and other features on the new fabric, remove it in large sections. Important: Take out any rib stitching fasteners before removing the fabric to avoid damaging the aircraft Preparation of the Airframe Before Covering After removing the old fabric, clean and inspect the airframe. Remove all old adhesive and address any necessary repairs or corrosion treatment. Many technicians also grit blast steel tube airframes at this stage. 25 General Fabric Covering Process 26 General Fabric Covering Process 27 General Fabric Covering Process 28 General Fabric Covering Process 29 After gluing the fabric, shrink it with a calibrated iron (use a smaller one for tight spots). Iron the entire surface according to instructions, shrinking evenly by working from one end to the other, then the middle. 30 31 END OF PART 1