Lesson-2-Fabrics

Aircraft Materials, Construction and Repair

  • Overview of materials and construction methods used in aircraft.

Aircraft Fabrics

  • Significance and role in aircraft structure and performance.

History of Aircraft Fabrics

Early Construction

  • Initial constructions used organic fabrics without special processes for strength.

  • Lack of airtightness; fabric would loosen and wrinkle with humidity.

  • Use of rubberized or varnished finishes applied to fabric surfaces to minimize airflow.

Cellulose Nitrate Improvement

  • Introduction of a clear dope made of cotton fibers dissolved in nitric acid for better durability.

  • Resulted in a translucent covering, exposing interior framework.

  • Deterioration from ultraviolet rays due to translucency.

Colored Enamel Application

  • Colored enamel applied over doped fabric to enhance sunlight protection.

  • Paint finishes suffered from cracking and peeling due to poor adhesion to dope coating.

Aluminum Powder in Dope

  • Manufacturers began mixing fine aluminum powder into dope for enhanced durability.

  • Resulted in a silver-colored dope that reflected heat and blocked sunlight.

Fire Hazard Solutions

  • High flammability of cellulose nitrate dope led to the development of cellulose acetate dope by the U.S. Navy.

Aircraft Fabric Covering

  • Refers to both the materials and processes for covering open structures in aircraft.

  • Fabrics must meet Technical Standard Order (TSO) standards, established by the FAA.

Approved Fabrics

  • Few approved fabrics for aircraft coverings include:

    • Ceconite

    • Stits/Polyfiber

    • Superflite

  • Use of unapproved materials is forbidden, leading to unairworthiness.

Fabric Terminology

  • Warp: Direction along the length of fabric.

  • Fill/Weave: Direction across the width of the fabric.

  • Count: Number of threads per inch in warp or filling.

  • Ply: Number of yarns in a thread.

  • Bias: Diagonal cut, fold, or seam.

  • Pinked Edge: Edge cut by special shears to prevent raveling.

  • Selvage Edge: Woven edge to prevent raveling.

  • Cross Coat: Technique of applying a second coat at a 90° angle to the first.

Other Fabric Covering Materials

Protective Materials

  • Anti-chafe Tape: Used on sharp edges and seams for protection.

  • Reinforcing Tape: Commonly used on rib caps for added strength.

  • Surface Tape/Finishing Tape: Applied after fabric installation for a neat finish.

  • Rib Lacing Cord: Strong cord used to secure fabric to wing ribs.

Additional Support Materials

  • Rib Bracing Tape: Applied spanwise around rib caps to keep ribs secured before covering.

  • Grommets: Reinforce drain holes in aircraft fabric made of aluminum or plastic.

  • Inspection Rings: Allow for inspections by maintaining shaped areas around fabric without cutting it.

Preparation Materials

  • Primer: Used to prepare airframe; typically two-part epoxy for metal and varnish for wood.

  • Fabric Cement: Attaches fabric to frame; must be compatible with primers and sealants.

  • Fabric Sealer: Provides a protective coating, blocking dirt and moisture; critical for UV protection.

  • Topcoats: Final protective and aesthetic layer after covering and sealing.

Aircraft Dope

  • Dope: Lacquer that tightens and weatherproofs fabric on aircraft.

Nitrate Dope

  • Bonds effectively to both fabric and structure but is highly flammable; less used today.

Butyrate Dope

  • Common and safer alternative; burns slowly and is more challenging to ignite.

Additives in Fabric Covering

  • Catalysts: Speed up chemical reactions; tailored for each product.

  • Thinner: Adjusts product consistency for proper application methods.

General Fabric Covering Process

Covering Methods

  • Blanket Method: Uses multiple flat fabric sections attached to airframe.

  • Envelope Method: Utilizes precut, pre-sewn fabric envelopes for quicker installation.