Southwest Research Institute Secures US Air Force Contract to Characterize Advanced Eddy Current Inspection for Aging Aircraft

Southwest Research Institute engineers develop low-frequency eddy current techniques to inspect aging Air Force aircraft without removing structural bushings.

By: AXL Media

Published: Mar 16, 2026, 10:40 AM EDT

Source: Information for this report was sourced from Southwest Research Institute

Revolutionizing Structural Integrity for Legacy Fleets

The Southwest Research Institute (SwRI) has entered into a new contract with the U.S. Air Force Academy to refine and characterize specialized inspection methods for repaired bolt holes in aging military aircraft. As airframes exceed their original design lives, maintaining structural integrity becomes increasingly dependent on sophisticated monitoring of high-stress areas. The current initiative focuses on "bushing-repaired" bolt holes, which are critical points of potential failure. By developing more precise characterization methods, SwRI aims to provide the Air Force with the data necessary to make informed repair decisions that ensure the continued safety of legacy fleets.

Eliminating the Risks of Bushing Removal

A primary challenge in current maintenance protocols is the physical handling of bushings, the cylindrical metal sleeves used to reinforce damaged bolt holes. Traditionally, these components must be removed to inspect the underlying material for cracks or wear, a process that inherently risks further damaging the airframe. Senior Research Engineer Nathan Richter, who oversees the project, noted that the removal and reinstallation process itself can introduce new stresses. The SwRI project seeks to bypass this risk entirely by validating techniques that allow for comprehensive inspection through the bushing, maintaining the structural status quo while gathering vital safety data.

Advanced Low-Frequency Eddy Current Applications

The technical heart of the SwRI program lies in the application of low-frequency eddy current testing. This nondestructive evaluation (NDE) technique utilizes electromagnetic fields to penetrate metallic surfaces and identify subsurface flaws. By utilizing lower frequencies, the electromagnetic waves can bypass the protective bushing to reach the underlying bolt hole structure. This method allows technicians to detect microscopic cracks without altering or dismantling the part. SwRI engineers are currently using coupons with purposefully generated flaws to test the sensitivity and limits of this electromagnetic approach under controlled laboratory conditions.