In production, every aircraft structure component will undergo inspection by one of the primary NDT methods. In-service aircraft will experience subsequent nondestructive testing, eddy current inspection being one the primary methods. This article serves to highlight the more common forms of eddy current applications on in-service aircraft.
With a few exceptions, general aviation aircraft are not pressurized at altitude. However, when business and commercial aircraft climb to altitude, e.g., 15,000 to 40,000 feet, the cabin is pressurized for passenger comfort. Since the pressure inside the cabin is greater than the outside, the fuselage will elongate and expand in diameter. When the aircraft lands and completes this flight cycle, the plane returns to its normal shape. This repetitive expansion and contraction eventually lead to metal fatigue and the possible initiation of cracks, whether it be fatigue cracking, stress corrosion cracking, or a stress rupture crack.