Identify a non-destructive testing method used in airframe maintenance.

The correct choice is ultrasonic testing, which is a non-destructive testing (NDT) method commonly used in airframe maintenance. This technique utilizes high-frequency sound waves to detect imperfections, such as cracks or voids, within a material without causing any damage to the structure being tested. By interpreting the reflections of these sound waves, inspectors can gather critical information about the internal condition of components, ensuring they are safe and structurally sound for continued operation.

This method is particularly advantageous in airframe maintenance due to its ability to provide precise measurements and locate flaws that may not be visible through surface inspections. The ability to assess the integrity of materials without impairing their usability makes ultrasonic testing a preferred choice for evaluating critical aircraft structures.

In contrast, visual inspections focus on detecting surface defects, while X-ray testing is another NDT method that uses radiation to identify internal flaws and is not always feasible for certain materials or geometries. Destructive testing, however, intentionally damages the component to assess its properties, which is contrary to the principles of non-destructive testing and is not typically used for routine airframe maintenance.