Airframe - Aircraft Fabric Covering

What is a tie-off knot?

A standard, modified seine knot used on all stitches except the starting stitch.

What is the principal advantage of the envelope method for covering wings?

Almost all the seams are machine-sewed by envelope supplier.

How would you determine the correct spacing for stitching if the original spacing was unknown?

Consult the chart in AC 43.13-1B.

What two types of organic fibers are used for covering aircraft?

Cotton and linen.

What types of synthetic fibers are used for covering aircraft?

Fiberglass and heat-shrinkable polyester fibers.

Which of the several types of fabric is unaffected by moisture and mildew?

Fiberglass.

What is the purpose of the selvage edge on a roll of fabric?

It prevents the fabric from unraveling.

Fabric is considered unairworthy when it has deteriorated to what percentage of its original strength?

Less than 70%.

Aircraft covering fabrics are made of material from what two sources?

Organic materials and synthetic materials.

Where would you use surface tape?

Over rib stitching and sewed seams, over lapped edges, around corners, and along leading and trailing edges.

Name three common types of machine-sewed seams.

Plain overlap, folded-fell, and French-fell.

What are the principle methods used to test the condition of fabric?

Punch testers such as the Maule or Seybolt tester, and laboratory pull-testing.

What is the function or purpose of reinforcing tape?

Reinforcing tape is used between the fabric and the rib stitching to prevent the lacing cord from cutting through the fabric.

What identification marking is found on the selvage edge, and in which direction is the warp applied?

The FAA-PMA stamp is found on the selvage edge and the warp is applied parallel to the line of flight.

How would you determine the strength requirements for fabric used to re-cover an aircraft?

The fabric must be of at least the quality and strength of the fabric used by the original manufacturer.

How are the fabric type and strength requirements determined for fabric-covered aircraft?

The original manufacturer determines the fabric type, and the strength requirements are a function of the never-exceed speed and wing loading.

How should a structure that will be covered with doped fabric be prepared following inspection and prior to covering?

Treat it with a protective coating of paint or varnish as appropriate.

Where are anti-tear strips used?

Under wing rib stitching when the never-exceed speed is greater than 250 mph.

What is meant by warp, weft, and bias?

Warp is the direction along the length of the fabric, weft is the direction across the the fabric at right angles to the warp, and bias is a direction at a 45 degree angle to the warp and weft.

How should the edges of drainage, inspection, and ventilation holes be reinforced?

With plastic, aluminum, or brass grommets.