Definition
A strip of aircraft fabric cut at a 45-degree angle to the weave (on the bias) and used during the fabric-covering process to cover seams, ribs, and reinforced areas on a fabric-covered aircraft. The bias cut allows the tape to stretch and conform smoothly around curved surfaces without fraying or wrinkling.
Plain English
A strip of aircraft fabric cut diagonally across the weave so it can stretch and shape itself neatly over seams and ribs when an aircraft is being covered with fabric.
Context Anchor
Seen during aircraft fabric covering and repair, especially when taping around curved areas such as wingtips, tail surfaces, inspection openings, or other shaped edges.
Derivation
‘Bias’ comes from Old French ‘biais,’ meaning slant or oblique. In sewing and fabric work, a bias cut is one made at 45 degrees to the threads of the weave, which gives the cloth elasticity it doesn’t have along the straight grain. That stretch is what makes the tape work on curved aircraft surfaces.
Why Pilots Care
Proper application keeps the fabric covering tight, aerodynamic, and resistant to wear, preserving both appearance and structural integrity.
Analogy
A straight-cut strip of cloth behaves like a stiff ribbon around a curve. A bias-cut strip behaves more like flexible trim, able to follow the curve without fighting it.
Intuition Check
“Bias” does not mean prejudice or an electrical setting here. In aircraft fabric work, it means the tape was cut diagonally across the fabric weave.
Example Sentence 1
During the annual inspection, the mechanic checked the bias-cut surface tape along each rib for signs of lifting or cracking.
Example Sentence 2
Bias-cut surface tape was laid along the wing leading edge to protect the fabric from abrasion and give a clean finish.