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Phased Array Inspection of Aerospace Fastener Holes

Published on 23rd November 2020

Phased Array Inspection of Aerospace Fastener Holes

Military forces around the world are extending the life of aging aircraft by using phased array ultrasound testing to detect cracks and other flaws to help prevent catastrophic failures.

One time-consuming challenge is inspecting aircraft fastener holes to detect faying (back wall) surface cracks.

Minimizing Aircraft Downtime

Reducing the downtime associated with inspecting aircraft is critical. Current inspection methods require a lengthy mechanical breakdown to allow inspectors access to all the critical fastener holes. During this time-consuming process, hundreds of overhead fasteners must be inspected.

The inspection area showing hundreds of overhead fasteners

Fast Fastener Inspection

To help inspectors complete their fastener inspections more quickly, Olympus created a small-access spinner probe with two shear wave linear arrays packaged in a cylindrical case. The case magnetically couples the probe around each raised fastener head, easing the inspection process.

The inspection results displaying three phased array groups—two groups of sectorial scan data for detecting cracks and a third group to check the quality of the coupling. The easy-to-interpret data is recorded in real time to visually display cracks detected in the C-scan and the couplant channel as a thin red line.

First, an inspector applies a light mist or couplant to the fastener. The probe then magnetically attaches to the fastener head, and the inspector turns the probe 180 degrees to achieve a full 360-degree inspection. The solution saves time and avoids the need for mechanical dissasembly.

Inspecting a fastner under an airplane

The results of inspecting a fastener using the probe


The Olympus small-access spinner probe improves coupling, detection, inspection time, and provides easy-to-interpret phased array ultrasound data. Please contact if you would like more information about this application, support for solving your own application, or need customized ultrasound transducers.

Images supplied by the US Naval F-5 Adversary Program.

Products used for this application

Phased Array Probes

Phased array application-specific probes have a range from 0.5 MHz to 18 MHz and may come with 16, 32, 64, or 128 elements. Special probes may have up to hundreds of elements.

Source: Phased Array Inspection of Aerospace Fastener Holes (

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