After tying wire bundles with cord, the square knot pigtails should be at least how many inches long?

• A. 1/4 inch
• B. 3/8 inch
• C. 1/2 inch
• D. 5/8 inch

Answer: (B)

When securing a wire bundle with cord, the tails left from the square knot—pigtails—need to be long enough to keep the knot from coming loose under vibration, while not so long that they snag on nearby components. The standard length for these pigtails in airframe practice is 3/8 of an inch. This length provides enough bite to maintain knot integrity during operation and makes the tails easy to inspect and trim without risking interference or snagging. Shorter tails can slip or wear more quickly; longer tails offer little extra security and increase the chance of contact with other parts.