Non-destructive inspection lab provides proactive maintenance to keep mission going

  • Published
  • By Tech. Sgt. Joel Mccullough
  • 445th Airlift Wing Public Affairs

Tucked away on the northeast corner of Wright- Patterson Air Force Base in building 4026 through a couple doorways and hallways inside the fabrication flight is an area marked as the “Non-Destructive In­spection Laboratory,” or NDI lab for short.

NDI is the inspection of a structure or component in any manner that will not impair its future useful­ness. The purpose is to detect flaws, measure geomet­ric characteristics, determine material structure or composition, or to characterize physical, electrical or thermal properties without causing any changes in the part.

“Our main job is to make sure there are no dis­continuities in these testing processes,” said Se­nior Airman Stephanie Gillispie, 445th Maintenance Squadron NDI inspector. “We make sure everything is structurally sound without destroying or permanently altering parts. That is why it is called non-destructive inspection.”

The five standard NDI disciplines include: liquid penetrant, magnetic particle, eddy current, radio­graphic testing and ultrasonic testing. They are used to detect subsurface flaws.

Gillispie, who is currently the only one filling a full-time position in NDI, not only works with large station­ary machines but also portable ones that she takes out to aircraft. She explained how the eddy current devices work while demonstrating some of the capa­bilities and everyday tasks she completes.

Eddy current testing uses electromagnetic induc­tion to identify defects. The process relies upon a ma­terial characteristic known as electromagnetic induc­tion. When an alternating current is passed through a conductor an alternating magnetic field is developed. Any changes in the conductivity of the material being examined, such as near-surface defects or differences in thickness, will affect the magnitude of the eddy cur­rent, resulting in spikes on her monitoring equipment.

“We use this technique to inspect components of a C-17 engine,” Gillispie said. “All defective parts are removed from the aircraft. We log everything via pa­perwork for the Air Force so that they can collect the data for research purposes.”

Gillispie also demonstrated the use of magnetic particles and liquid penetrants. One of the larger ma­chines in the lab is the magnetic particle bath. It uses a fluorescent oil combined with magnetic dust parti­cles to penetrate and identify defects in parts.

“I like my job,” said Gillispie with a smile. “It’s nerdy, and I’m a nerdy person.”

Also, inside the back shop is an inspection booth that looks similar to a photo booth. The booth uses ultraviolet lamps combined with liquid penetrants to detect surface level flaws. The liquid penetration tech­nique requires an inspector to use a cleansing chemi­cal, dye and developer to detect the flaws properly.

“We use these processes to detect things that are not technically visible to the naked eye,” Gillispie ex­plained. “It's one of my favorite processes.”

The inspector went on to explain there are many different causes for defects or cracks in parts, includ­ing stress fatigue, impact and major accidents.

She said there can also be corrosion stress fatigue cracks, adding that, “those are my least favorite be­cause they take the longest.”

The final piece of NDI is the X-ray control room. Although it is currently under construction as it is undergoing a major upgrade, Gillispie explained how their X-ray uses gamma radiation to take photographs, or X-rays, of parts. The system they are upgrading will take the system from a chemical process of photogra­phy to a completely digital one.

“This is my favorite system, so I am hoping to get it up and running as soon as possible,” Gillispie said.

When the 445th MXS fabrication flight won MXS of the year for 2022 at the Air Force Reserve Command level, Chief Master Sgt. Clifton Griffie, 445th MXS se­nior enlisted leader, highlighted how NDI is an impor­tant piece of maintenance, discovering issues before they might have a bigger negative impact on the mis­sion.

“They’ll go out, and they’ll verify wheels,” he said. “When they break down the wheels, they’ll check them for cracks and check bolts for cracks, so it’s a lot of preventative maintenance as well, not necessarily a reactiveness, but also proactive.”