Lesson-2-Fabrics

AIRCRAFT MATERIALS, CONSTRUCTION AND REPAIR

AIRCRAFT FABRICS

HISTORY OF AIRCRAFT FABRICS

  • Early Materials: Organic fabrics used with no special processes for strength.

  • Initial Improvements: Coatings (rubberized or varnished) applied to mitigate humidity effects.

MATERIALS AND TECHNIQUES

  • Cellulose Nitrate Development:

    • Cotton fibers dissolved in nitric acid created a more durable finish.

    • Resulted in translucent coverings that exposed internal frameworks.

    • Translucency led to degradation from UV exposure.

  • Improved Coating Techniques:

    • Colored enamel painted over doped fabric to block sunlight.

    • Paint prone to cracking due to poor adhesion, reducing effectiveness.

  • Aluminum Powder Addition:

    • Fine aluminum powder mixed into dope for a reflective silver finish, decreasing heat absorption and improving durability.

  • Fire Safety Enhancement:

    • Development of cellulose acetate dope by US Navy to decrease flammability hazards of nitrate dope.

AIRCRAFT FABRIC COVERING

  • Definition:

    • Refers to both the materials and the process for covering aircraft structures.

    • Must meet FAA’s Technical Standard Order (TSO) for approval.

  • Approved Fabrics:

    • Only a few approved polyester fabrics such as Ceconite, Stits/Polyfiber, and Superflite.

    • Substitution of unapproved materials renders aircraft unairworthy.

FABRIC TERMS

  • Key Terminology:

    • Warp: Fabric length direction.

    • Fill/Weave: Fabric width direction.

    • Count: Threads per inch in warp or fill.

    • Ply: Yarns that compose a thread.

    • Bias: Diagonal cut relative to warp or fill.

    • Pinked Edge: Edge finished with pinking shears.

    • Selvage Edge: Finished edge to prevent raveling.

    • Cross Coat: Technique for applying second coat perpendicular to the first.

ADDITIONAL MATERIALS FOR FABRIC COVERING

  • Anti-Chafe Tape:

    • Protects sharp edges and seams to prevent fabric damage.

  • Reinforcing Tape:

    • Strengthens rib caps after installation.

  • Surface Tape:

    • Finishing tape applied post fabric installation.

  • Rib Lacing Cord:

    • Secures fabric to wing ribs, ensuring load transfer.

  • Rib Bracing Tape:

    • Applied spanwise to hold ribs during covering.

  • Grommets:

    • Reinforce drain holes, preventing fraying.

  • Inspection Rings:

    • Create stable viewing holes in fabric for structural checks.

  • Primer:

    • Prepares structure for fabric covering with epoxy-based treatments.

  • Fabric Cement:

    • Attaches fabric securely, must be compatible with sealants used.

  • Fabric Sealer:

    • Protects fibers, blocks dirt/moisture, and prevents UV damage through filler application.

  • Topcoats:

    • Final appearance layer applied after sealing and filling.

AIRCRAFT DOPE

  • Definition:

    • Plasticized lacquer applied to fabric to ensure tight, weatherproof coverings.

  • Nitrate Dope:

    • Offers better adhesion but highly flammable; less commonly used today.

  • Butyrate Dope:

    • Popular for safety, burns slowly compared to nitrate dope.

ADDITIVES

  • Catalysts:

    • Accelerate chemical reactions specific to each product.

  • Thinner:

    • Mixture added for proper application consistency.

GENERAL FABRIC COVERING PROCESS

  • Blanket Method:

    • Involves multiple fabric sections secured to the airframe.

  • Envelope Method:

    • Utilizes pre-cut, pre-sewn fabric envelopes for efficient covering.