Apparatus and Method for Second-Layer Through-Bushing Inspection of Aircraft Wing Attachment Fittings Using Electric Current Perturbation

An electric current perturbation (ECP) probe for detecting anomalies in a structure surrounding a fitting aperture, the ECP probe comprising:

• (a) a probe body sized and structured for insertion into the fitting aperture to maintain contact with an interior wall of the aperture, the probe body generally cylindrical in configuration and having a handle end and a sensor end;
• (b) a compliant mechanism positioned on the probe body at the sensor end thereof, the compliant mechanism comprising a sensor contact element and an expansion element, the sensor contact element comprising a cylindrical section movable in a direction generally orthogonal to a long axis of the probe, and the expansion element preferencing the sensor contact element against the interior wall of the aperture upon insertion of the probe into the aperture, the expansion element comprising at least one spring positioned and compressed between the sensor contact element and the balance of the sensor end of the probe body;
• and
• (c) an ECP sensor system positioned on the sensor contact element of the compliant mechanism, the ECP sensor system comprising a drive coil with a ferrite core and a differential receive coil, the differential receive coil positioned adjacent the drive coil and ferrite core in a manner that shields the receive coil from extraneous interferences.

A method for the inspection of aircraft structural component attachment fittings, the method capable of being carried out without the necessity of removing the aircraft structural components from each other, the method comprising:

• (a) removing, one at a time and in turn, each of a plurality of fasteners associated with the attachment fittings between the structural components, the removal of the fastener exposing a fitting aperture;
• (b) providing a compliant electric current perturbation (ECP) probe, the probe comprising a compliant mechanism positioned on a probe body for preferencing a probe sensor element against an interior wall of the fitting aperture;
• (c) inserting the ECP probe into the fitting aperture so as to establish compliant contact between the probe sensor element and the interior wall of the aperture;
• (d) providing an interrogation drive signal to the ECP probe sensor element;
• (e) receiving a return signal from the ECP probe, the return signal containing signal characteristics indicative of a presence or absence of anomalies in a structural area surrounding the fitting aperture;
• and
• (f) discriminating an anomaly signal from interference components of the return signal, wherein the discrimination of the anomaly signal characteristics is facilitated by shielding the probe sensor element.

A method for the inspection of aircraft structural component attachment fittings, the method capable of being carried out without the necessity of removing the aircraft structural components from each other, the method comprising:

• (a) removing, one at a time and in turn, each of a plurality of fasteners associated with the attachment fittings between the structural components, the removal of the fastener exposing a fitting aperture;
• (b) providing a compliant electric current perturbation (ECP) probe, the probe comprising a compliant mechanism positioned on a probe body for preferencing a probe sensor element against an interior wall of the aperture, the ECP probe further comprising a drive coil/core and a receive coil, the receive coil positioned in a manner such that the drive coil/core shields the receive coil from extraneous interferences;
• (c) inserting the ECP probe into the fitting aperture so as to establish compliant contact between the probe sensor element and the interior wall of the aperture;
• (d) providing an interrogation drive signal to the drive coil/core of the ECP probe;
• (e) receiving a return signal with the receive coil of the ECP probe, the return signal containing signal characteristics indicative of a presence or absence of anomalies in a structural area surrounding the fitting aperture;
• and
• (f) discriminating an anomaly signal from interference components of the return signal, wherein the discrimination of the anomaly signal characteristics is facilitated by shielding the probe sensor element.