FAA Aviation Mechanic Airframe (AMA)Airframe StructuresEasy
A technician is checking the strength of an in-service fabric-covered airplane wing using a calibrated field test instrument pressed against the surface. What is this common field test called, and what does it evaluate?
- ACoin-tap test, evaluating disbonded honeycomb core
- BTorque test, evaluating fastener preload
- CEddy current test, evaluating metal fatigue cracks
- DPunch (fabric strength) test, evaluating remaining fabric tensile strength
Show answer & explanationAnswer & explanation
Correct answer: D. Punch (fabric strength) test, evaluating remaining fabric tensile strength
A punch test, performed with a calibrated field tester such as a Maule tester, measures the force required to push a small probe through the fabric, giving an estimate of the fabric's remaining tensile strength compared to the minimum required strength (per ASTM D3999 or the applicable standard) for continued airworthiness.
Why the other options are wrong
- A. The coin-tap test is used on composite sandwich panels, not fabric coverings.
- B. Torque testing checks fastener tightness, unrelated to fabric strength.
- C. Eddy current testing is used on conductive metal structures, not fabric.
Fabric Punch Test
A field test using a calibrated punch tester pressed against fabric covering to estimate its remaining tensile strength for airworthiness determination.
- Common tester: Maule fabric strength tester
- Compares result to minimum strength requirement (e.g., ASTM D3999)
- Deteriorated fabric strength below minimum requires recovering
Memory trick: 'Punch it to see if it will crunch' — testing fabric's remaining strength.