Timely maintenance of aircraft structures is critical to keeping our armed forces aircraft fleet operational. Defects greatly impact the stability and integrity of the aircraft, and if left undetected can result in extended removal of the aircraft from service, or possibly even lead to disaster. Since most of the defects and fractures occur beneath the skin on the plane, visual inspection is insufficient. Eddy current testing (ECT) is one of the nondestructive inspection (NDI) technologies used for detection and classification of defects. The present methods of ECT inspection of aircraft require two separate scans at different frequencies, one for shallow defects near the top surface and one for defects at or near the underside of the skin. Running two scans and changing the scanning apparatus in between leads to long, costly maintenance times. A faster and more efficient way to do NDI would decrease the cost of maintenance and the downtime of each aircraft. RMD is addressing this by developing a hybrid multimode ECT-based scanning technology, which has higher sensitivity than traditional ECT methods, and can scan both sides of the skin in a single pass by simultaneously using multiple frequencies. This hybrid technology promises to reduce the inspection time to one half to one quarter of the time presently needed to inspect an airplane. The NDI technique being developed for this application is a breakthrough in eddy current testing, yet it uses existing commercial off the shelf components, facilitating implementation and user acceptance. The technology can be used for a variety of NDI procedures on both military and commercial aircraft. These include: 1. Simultaneous inspection of outer and inner fuselage surfaces; 2. Detection of subsurface flaws in aircraft; 3. Evaluating bonded lap joints; 4. Inspection of welds.
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