ANDI’s design was dictated by the FAA’s state of mind and by the state of NDI technology around 1990, when the project was defined and begun. The state of mind at the time, still dominated by the Aloha incident of 1988, was that large scale eddy current “fishing expeditions” are a desirable way to head off future Alohas, and that large scale instrumented inspection could be made palatable to commercial airline operators if there were an economically acceptable automated device to deploy the sensors.

The state of technology for eddy current sensors at the time was mainly manually manipulated point probes and complex impedance plane displays of their signals. These circumstances led to a design that maneuvers most gracefully along long fore-aft lines of rivets, maintaining precision alignment with them so that an eddy current pencil probe scanned parallel to the line of motion would follow the desired scanning path with little or no need for additional closed loop path control.