What does a flush patch typically consist of?

A flush patch is designed to repair damage on aircraft surfaces in a way that maintains the aerodynamic profile and structural integrity of the surrounding aircraft skin. The correct answer, which states that the filler should be the same thickness and alloy as the skin, is essential for several reasons.

Using a filler that matches the thickness of the original skin ensures a smooth, even surface that can withstand the same stresses and strains as the surrounding material. If the filler were thicker, it could disrupt airflow, leading to turbulence that might affect the performance of the aircraft. Additionally, matching the alloy is crucial for maintaining compatibility in terms of mechanical properties and corrosion resistance. Different alloys can exhibit differing rates of expansion and contraction, which could introduce stresses at the patch boundary, leading to potential failure over time.

In summary, consistency in both thickness and alloy for the filler in a flush patch is necessary to ensure that the repair is effective and that the structural and aerodynamic performance of the aircraft is not compromised.