Aircraft Fabric Coverings and Materials

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are the primary materials used for fabric coverings in aircraft before the 1960s?

Synthetic leather and canvas

Grade A cotton and Irish linen (correct)

Polyester and glass fibre

Synthetic rubber and nylon

What major drawback do natural fabric coverings have compared to synthetic fabrics?

Incompatibility with standard aircraft designs

Greater susceptibility to UV light and flammability (correct)

Reduced structural integrity over time

Higher cost and difficulty in application

What is a significant advantage of synthetic fabric coverings over natural fabrics?

Lower cost and easier application

Improved aesthetic appeal

Enhanced resistance to moisture

Longer replacement intervals and reduced maintenance (correct)

What is a critical concern regarding the long replacement intervals of synthetic fabrics?

Greater intervals between airframe structural inspections Signup and view all the answers

Which of the following is NOT a synthetic fabric used in aircraft coverings?

Linen Signup and view all the answers

What must be completely removed for a comprehensive structural inspection of an aircraft?

The synthetic fabric covering Signup and view all the answers

What is the main factor that led to the widespread adoption of synthetic fabrics in aircraft?

Increases in cost and the short lifespan of natural fabrics Signup and view all the answers

Why is fabric orientation important in aircraft fabric coverings?

It is crucial for ensuring a strong covering. Signup and view all the answers

What direction do the warp threads run in a fabric?

Along the length of the fabric Signup and view all the answers

Which fabric has a strength of around 140 lb/in when new?

Irish Linen Signup and view all the answers

What is the purpose of the selvage edge in fabric?

To prevent the fabric from unraveling Signup and view all the answers

What is a characteristic of bias fabric orientation?

It allows for the formation of contoured shapes Signup and view all the answers

What happens to polyester fabric when heat is applied during installation?

It constricts back to its original length Signup and view all the answers

Which of the following statements is true about glass fibre?

It must be tensioned when fitted. Signup and view all the answers

How is Grade A cotton strengthened during manufacturing?

By mercerization in a caustic soda solution Signup and view all the answers

What is a characteristic of synthetic polyester fabrics?

They have equal number of fibres in warp and fill directions. Signup and view all the answers

What does a pinked edge refer to?

An edge cut with special shears to prevent unraveling Signup and view all the answers

What is greige fabric?

Unshrunk fabric just removed from the loom Signup and view all the answers

What protects polyester fabric from deterioration due to ultraviolet radiation?

Coatings applied during manufacturing Signup and view all the answers

Which tape is used to smooth sharp protrusions and prevent fabric tearing?

Anti-chafe tape Signup and view all the answers

What is the primary function of inter-rib bracing?

To maintain rib alignment during shrinking Signup and view all the answers

What is a notable risk associated with excessive heat applied to polyester fabric?

It can melt and burn Signup and view all the answers

What is the primary use of surface tape in aircraft covering?

To blend the covering around seams and contours Signup and view all the answers

Why is rib-lacing cord important in aircraft fabric covering?

It helps prevent fabric from tearing and maintains aerofoil shape. Signup and view all the answers

What is the function of grommets in aircraft fabric?

To create reinforced drain holes for moisture management. Signup and view all the answers

How do inspection rings assist in aircraft maintenance?

They allow access to critical areas after fabric application. Signup and view all the answers

What is the main purpose of using special fabric fasteners in aircraft covering?

To fasten the fabric to ribs using various approved methods. Signup and view all the answers

Which tool is used to monitor fiber surface temperatures during fabric work?

Fibre thermometer Signup and view all the answers

What is the role of aircraft dope in fabric covering?

It protects fabric from environmental damages. Signup and view all the answers

Which type of dope is known for being highly flammable due to its composition?

Cellulose Nitrate Dope Signup and view all the answers

What is required before using fabric covering tools that involve heat for shrinkage?

They must be calibrated for temperature settings. Signup and view all the answers

How does proper application of dope affect fabric covering?

It helps in reducing air passage through the fabric. Signup and view all the answers

What must be done if fastener holes become worn before applying special fabric fasteners?

Enlarge or re-drill them as per manufacturer’s instructions. Signup and view all the answers

Which of the following tools is specifically used to create a continuous series of Vs to prevent unravelling of fabric edges?

Pinking shears Signup and view all the answers

What characteristic of cellulose nitrate dope makes it a less preferable option nowadays?

It is highly flammable and poses safety risks. Signup and view all the answers

What must be controlled during the dope application process to ensure a proper finish?

Humidity and temperature conditions Signup and view all the answers

What is the primary concern when seaming fabric on an aeroplane?

Strength, elasticity, durability, and appearance Signup and view all the answers

What method should be used to sew the blanket on aeroplanes with a Vmo greater than 150 mph?

Plain overthrow or baseball stitch Signup and view all the answers

What is the minimum breaking strength required for the fabric to remain airworthy if it was originally rated at 80 lb?

56 lb Signup and view all the answers

What is essential to do before applying the fabric to the airframe structure?

Apply adhesive in two coats and allow to dry Signup and view all the answers

What is the main reason for re-covering an aircraft's fabric?

Deterioration of fabric strength Signup and view all the answers

What temperature does polyester fabric shrink nearly 10%?

350 °F (176 °C) Signup and view all the answers

Which materials are essential for personnel protection during the fabric covering process?

Eye protection, a respirator, and skin protection Signup and view all the answers

What method is commonly used to attach fabric to wing ribs in aircraft?

Screws, rivets, clips, and lacing Signup and view all the answers

What is rib lacing designed to prevent?

Fabric blowing away from the structure Signup and view all the answers

What is the purpose of anti-chafe tape when covering an aircraft?

To prevent chafing at contact points Signup and view all the answers

Which covering method involves pre-sewn envelopes to minimize installation hand-stitching?

Envelope method Signup and view all the answers

What type of knot is typically used for the first stitch when lacing a rib?

Square knot with a half hitch Signup and view all the answers

For aeroplanes with a maximum operating velocity greater than 220 knots, what should be used under rib stitching?

Anti-tear strips Signup and view all the answers

What should be ensured about the aircraft before covering it with new fabric?

All repairs completed and structures moisture protected Signup and view all the answers

What is the minimum frequency for determining the breaking strength of fabric coverings during inspections?

Every 100 hours and annual inspections Signup and view all the answers

What is required after covering seams and rib stitching with surface tape?

Saturate the tape with dope Signup and view all the answers

What is typically required in the work environment for proper fabric covering preparation?

Control of temperature, humidity, and ventilation Signup and view all the answers

What is a common material used to cement polyester fabric to the airframe structure?

Fabric cement or glue Signup and view all the answers

What primary issue can excess tension in fabric cause in aircraft structures?

Warping of critical components Signup and view all the answers

Why is it important to remove any rib-stitching fasteners before pulling fabric free from the airframe?

To prevent damage to the structure Signup and view all the answers

What should avoid being too tight when positioning the fabric on the structure?

The fabric's relaxed condition Signup and view all the answers

Which factor is a common cause of loose or wrinkled fabric in aircraft?

Excess slack during installation Signup and view all the answers

What is a common characteristic of polyester fabric used in aircraft re-covering?

It exceeds certain strength requirements for airworthiness Signup and view all the answers

What process follows after the fabric has been glued to the structure?

Heat shrinking to make it taut Signup and view all the answers

What is the recommended method for repairing polyester fabric coverings?

Cemented repairs without sewing Signup and view all the answers

What is the role of ventilation when working with materials like nitrate dope?

To prevent toxic fume accumulation Signup and view all the answers

What type of stitch is preferred due to its strength and durability for sewing polyester fabric?

Doped seam Signup and view all the answers

How should metal parts be treated prior to applying new fabric covering?

They must be coated with a good-quality epoxy primer Signup and view all the answers

Which issue results from cracks in the coatings of aircraft fabric?

Deterioration of exposed fabric Signup and view all the answers

What should workers do to prevent static electricity build-up during the covering process?

Ground the work area Signup and view all the answers

What must all materials used for fabric repairs match?

Quality and type of original materials Signup and view all the answers

What is the function of jigs and work stands during the fabric covering process?

To maintain structural integrity of parts Signup and view all the answers

How should areas showing lifting fabric covering be addressed?

Seal or remove coatings and replace with new materials Signup and view all the answers

What is the major risk of excess dope film on new fabric covers?

Causes excess tension in the fabric Signup and view all the answers

What is the primary advantage of butyrate dope over nitrate dope?

It burns slower and is less easily ignited. Signup and view all the answers

Why is a fungicidal paste applied to untreated cotton and linen fibres?

To kill airborne spores of fungus and mildew. Signup and view all the answers

What is a common consequence of insufficient dope film quality?

Loose or wrinkled fabric covering Signup and view all the answers

What should be given particular attention during fabric inspections on aircraft?

Areas within the propeller slipstream Signup and view all the answers

What is a primary use of plasticisers in dope formulations?

To give resilience to the film. Signup and view all the answers

What does the general procedure for inspecting a damaged fabric area involve?

Confined damage assessment of the fabric Signup and view all the answers

Which type of dope is typically recommended for heat-shrunk polyester fabrics?

A special blend of nitrate and butyrate dopes. Signup and view all the answers

What is the purpose of adding a retarder to dope?

To prevent blush from forming. Signup and view all the answers

How do aluminium flakes help in dope applications?

They block ultraviolet rays from damaging materials beneath. Signup and view all the answers

What characteristic makes synthetic dopes suitable for initial base coats in certain aircraft coverings?

Their effective adhesion characteristics. Signup and view all the answers

What happens to dope films over time due to ultraviolet rays?

They lose their resilience and become brittle. Signup and view all the answers

What are fabric primers used for in covering processes?

To seal fabrics and improve adhesion for coatings. Signup and view all the answers

Which type of dope has the best encapsulation characteristics for attaching fabric to the structure?

Nitrate dope. Signup and view all the answers

What is a common function of accelerators in dope applications?

To increase drying speed in cold conditions. Signup and view all the answers

What significant difference does modern synthetic fabric covering present compared to traditional methods?

They are lighter, economical, and easier to repair. Signup and view all the answers

What is the main drawback of butyrate dope compared to nitrate dope?

It does not encapsulate fibres as effectively. Signup and view all the answers

What is the role of thinner in dope application?

To provide the proper consistency for application. Signup and view all the answers

What is the primary purpose of installing fabric gussets?

To reinforce areas around cable guides and strut-attach fittings Signup and view all the answers

What type of dope is applied as a sealer coat before rib stitching?

Non-tautening nitrate dope Signup and view all the answers

Which area should be prioritized for inspection due to rapid deterioration?

Areas exposed to direct sunlight and temperature fluctuations Signup and view all the answers

What is a significant cause of deterioration in polyester fabric used for aircraft?

UV light Signup and view all the answers

What indicates that a fabric needs replacement during testing?

If a puncture occurs near breaking strength Signup and view all the answers

What is the method used to determine the breaking strength of aircraft fabric?

A weight suspension test on a sample strip Signup and view all the answers

Which of the following is true about the Seyboth tester?

It punctures a small hole in the fabric during the test Signup and view all the answers

What should be done if excessive deterioration is found during an inspection?

Perform necessary repairs to restore fabric strength Signup and view all the answers

What is one consequence of fabric inspection stripping?

It can damage the integrity of an airworthy component Signup and view all the answers

What is the purpose of the cross coats of Butyrate dope applied after sealing?

To protect against UV light Signup and view all the answers

What type of fabric is susceptible to accelerating deterioration when darker colors are used?

Both organic cotton and synthetic fabrics Signup and view all the answers

How often should fabric inspections be performed?

Periodically as routine procedures Signup and view all the answers

Why might engineers prefer non-destructive testing techniques over cutting test strips?

It avoids damaging airworthy fabric components Signup and view all the answers

What type of coating is applied in the final three coats before finishing?

A colored Butyrate dope or Polyurethane Signup and view all the answers

Study Notes

Early Fabric Coverings

Majority of aircraft fabric coverings before the 1960s used organic materials like Cotton and Linen.
Fabric was treated with dope to tighten and protect it from moisture and sunlight.
Post-1960s, synthetic fabrics (e.g., polyester, glass fiber) emerged as the new standard.
Natural fabrics face issues such as flammability, mildew, and UV sensitivity, necessitating replacement every 10 years.
Synthetic fabrics can last up to 25 years, increasing the risk of undetected structural deterioration due to less frequent inspections.

Modern Synthetic Fabric Coverings

Cost and durability shifted nearly all aircraft coverings to synthetic, STC-approved materials.
Common synthetic fabrics include Ceconite®, Poly-Fiber®, and Superflite®.
Effective structural inspection requires complete fabric removal.

Fabric Orientation and Key Terms

Fabric Orientation: Critical for maintaining structural integrity; orientation begins with placement and use of reinforcing materials.
Warp and Fill: Warp threads run lengthwise (0° direction), while fill threads run perpendicular (90°). More threads in warp make it stronger.
Selvage Edge: Tightly woven edge parallel to the warp that prevents fraying; must be removed before application.
Bias: Fabric orientation at 45° to warp, allowing easier manipulation for shapes.
Thread Count: Refers to threads per inch in warp or fill.
Pinked Edge: Fabric cut in Vs for fray prevention.
Greige Fabric: Unshrunk polyester fabric straight from the loom.

Organic Fabric Materials

Grade A Cotton: Mercerised for strength and durability; identified by its off-white color.
Irish Linen: Made from flax, stronger than cotton (140 lb/in), historically common in aircraft but replaced largely by synthetic options.

Inorganic Fabric Materials

Polyester Fabric: Durable, resistant to moisture and chemicals but vulnerable to UV radiation, requiring protective coatings.
Glass Fiber: Stronger than cotton and polyester, not prone to moisture decay, but must be tensioned during installation.

Additional Fabric Covering Materials

Anti-Chafe Tape: Self-adhesive cloth tape used to protect areas prone to wear.
Reinforcing Tape: Used under rib lacing to prevent pull-through.
Surface Tape: Covers seams for a smoother finish and prevents loosening during flight.
Rib-Lacing Cord: Secures fabric to ribs, preventing lift-induced fabric detachment.

Fabric Covering Tools

Fabric Iron: For heat-shrinking synthetic fabrics; must be temperature calibrated.
Sealing Iron: Small iron for tight spaces, requiring similar calibration.
Stitch Needles and Spring Clamps: Various needle types for sewing and clamps for holding fabric.
Fibre Thermometer: Monitors surface temperatures during heat application.
Pinking Shears and Sharp Blades: For preparing fabric edges and cutting processes.

Aircraft Dope

Refers to cellulose-based coatings used to protect fabric from environmental harm.
Types include nitrate, butyrate, and synthetic dopes, each serving specific adhesive and protective functions.
Must control application temperature and humidity for best results, and good ventilation is critical due to toxicity.

Dope Types

Nitrate Dope: Highly flammable, historical, used for adhesion and fabric finishing.
Butyrate Dope: Less flammable, used extensively today with better tautening properties.
Synthetic Dopes: Modified for flexibility and reduced tautening in polyester fabrics.

Additives, Primers, and Coatings

Fungicidal Paste: Used on organic fibers to kill potential mildew or fungus.
Rejuvenator: Restores flexibility by softening and reintroducing plasticisers to degraded dope.
Aluminium Paste: Blocks UV rays, applied as a final protective layer.
Retarders and Accelerators: Adjust drying times based on application conditions.

Covering Procedures

Modern synthetic coverings are lightweight, economical, and visually appealing.
Repair and maintenance processes differ significantly from those for metallic and composite structures.### Fabric Maintenance and Repair in Aircraft
Covering materials and attachment methods vary significantly between aircraft models, impacting durability and repair strategies.
Major repairs include the replacement of fabric coverings, which must adhere to aviation regulations and be performed by authorized personnel.
Fabric is airworthy until its strength deteriorates below 70% of the original breaking strength; for example, Grade A cotton's breaking strength becomes un-airworthy at 56 lb from a new strength of 80 lb.
Regular inspections at 100-hour intervals and annual checks assess fabric strength to determine the necessity of re-covering.

Preparation for Fabric Covering Work

Workshop environment should control temperature, humidity, and ventilation; additives can help if ideal conditions aren't attainable.
Essential tools include jigs for tracking structural integrity and proper safety gear due to toxic substances involved in the covering process, like nitrate dope.
Disassembly of the aircraft is necessary to access and inspect structural components prior to installing new fabric.

Fabric Covering Methods

Envelope Method: Pre-sewn envelopes minimize hand-stitching during installation, aligning seams with the wing’s structure.
Blanket Method: Involves wrapping a large piece of fabric around the wing, requiring careful sewing or doping to ensure integrity; less common in high-velocity aircraft due to labor intensity.

Seams and Adhesion

Fabric seams should maximize strength and durability, typically placed over structural components.
Polyester fabric is usually glued rather than sewn; a multi-step adhesive application is required for proper attachment.
Heat shrinking post-adhesion ensures tautness without damage; care must be taken to follow temperature protocols.

Rib Lacing and Gussets

Rib lacing secures fabric to wing ribs using cord to prevent billowing; method involves pre-punched holes for cord passage.
Gussets reinforce areas around cable openings and strut fittings, preventing wear and structural breaches.

Coating the Fabric

A sequence of coats, often involving nitrate dope, provides waterproofing and UV protection; critical for extending fabric life.
Coating procedures vary by manufacturer but generally include application of sealer coats and cross coats.

Inspections and Testing

Routine inspections should focus on high-risk areas (e.g., sun exposure, heat absorption) and assess for physical wear or decay.
Testing devices like the Maule and Seyboth testers help gauge fabric strength; however, substantial holes result from testing, indicating a need for repairs.

Common Fabric Defects

Excess Tension: Observable tension issues can warp airframe components; often due to dope film shrinking over time.
Loose Fabric: Muffling or rippling in flight indicates improper installation or structural issues; polyester coverings are particularly sensitive to slack and heat application.

Conclusion

Maintaining fabric integrity is vital for aircraft safety; adherence to inspection schedules, preparation protocols, and proper repair methods ensures longevity and performance of aircraft coverings.### Fabric Coating and Wrinkles
Temporary wrinkles can appear in fabrics coated with dope due to moisture from rain, fog, or dew, causing expansion of poor-quality dope film.
Moving aircraft from cold to warm environments can induce wrinkles from rapid thermal expansion of thick coatings.

Coating Cracks

Cracks in coatings expose fabric to deterioration, necessitating sealing or removal of the compromised coatings.
Immediate area repair involves applying new coatings or recovering the component to maintain integrity.

Fabric Repair in Aircraft

Aircraft fabric repairs are essential; damaged areas must be assessed to ensure that only the fabric is affected, avoiding structural damage.
Repair materials must match or exceed original material quality and type, ensuring airworthy conditions are restored.

Repair Instructions and Considerations

Identify the fabric type used for the covering in need of repair through logbook references or manufacturer data.
The nature of repairs is influenced by the extent of damage and fabric type, with many repairs utilizing new adhesives per STC procedures.
Cotton fabric repairs often involve sewing, while polyester fabric repairs predominantly use cementing techniques.
Repair instructions for polyester fabric focus on cemented methods, preferred by technicians for simplicity and maintained strength over sewn methods.

Example of Fabric Repair

When fabric is cut, the surrounding area is stitched, tensioned, and then covered with surface tape for finishing to ensure durability.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the evolution of aircraft fabric coverings from organic materials like cotton and linen to modern synthetic fabrics such as polyester and glass fiber. This quiz delves into the advantages and disadvantages of each type, along with key terms such as fabric orientation. Test your knowledge on how these materials impact aircraft maintenance and safety.