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173rd Fighter Wing structural innovation helps keep aircraft aloft

Part Fabrication

U.S. Air Force Master Sgt. Paul Allen, a structural maintainer with the 173rd Fighter Wing, places a part in the “smash-box”, a reinforced steel container lined with thick, durable rubber which shapes the flat aluminum part when placed under extreme pressure, Nov. 5, 2021. Structural maintainers at Kingsley Field in Klamath Falls, Ore., designed this process to reproduce parts no longer available in the supply system both here and at other units thereby cutting the cost of creating each part individually by hand. (U.S. Air National Guard photo by Master Sgt. Jefferson Thompson)

Part Fabrication

A schematic drawing shows the exact location of a part the 173rd Fighter Wing structural maintenance shop is tasked with fabricating, a process that in the past required a combination of craftsmanship, skill and time as each part was hand-formed using wood molds and delicate hammer strokes. That process is something the maintainers at Kingsley Field in Klamath Falls, Ore., are hoping to leave behind as technology is helping revolutionize part fabrication at the unit level. (U.S. Air National Guard photo by Master Sgt. Jefferson Thompson)

Part Fabrication

U.S. Air Force Master Sgt. Paul Allen, a structural maintainer with the 173rd Fighter Wing, uses modeling software and a scanning camera to create an exact replica of the plaster mold on his left at Kingsley Field in Klamath Falls, Ore., Nov. 11, 2021. This technology allows for the creation of exact molds and facilitates the 173rd Structural Maintenance shop creating replacement parts in less than half the previous time needed with old methods. (U.S. Air National Guard photo by Master Sgt. Jefferson Thompson)

Part Fabrication

U.S. Air Force Master Sgt. Paul Allen, a structural maintainer with the 173rd Fighter Wing, selects a mold used to create parts from a drawer of wooden molds he and others created to form parts for the F-15C fleet at Kingsley Field in Klamath Falls, Ore., Nov. 5, 2021. In order to create parts that no longer exist in the supply system, wooden molds are used to gently shape sheet metal parts with a hammer and other hand tools, a time-intensive process requiring craftsmanship and skill. (U.S. Air National Guard photo by Master Sgt. Jefferson Thompson)

Part Fabrication

U.S. Air Force Master Sgt. Paul Allen, 173rd Fighter Wing structural maintenance technician, points out a point-of-failure on a mold cast from dental plaster, rather than wood, which structural maintenance team used to shape a fairing rib on an F-15C, Nov. 5, 2021 at Kingsley Field in Klamath Falls, Ore. 173rd FW Maintainers found using a hammer to form the metal around the mold immediately cracked it. (U.S. Air National Guard photo by Master Sgt. Jefferson Thompson)

KINGSLEY FIELD, Ore. --

For years structural maintainers have emerged as artisans of sorts, creating parts by hand, meticulously shaping them from custom wood forms and delicate hand-tool work.

Gently tapping away with a small hammer, slowly giving shape to a sheet of aircraft-grade aluminum so it will slide into the tight confines of an F-15 fuselage with an expected tolerance of .005 of an inch.

This is necessary because of the thousands upon thousands of parts that make up an F-15C, many of them don’t exist in the supply system any longer—they haven’t for decades.

“It’s a 50-50 shot when you need a part that it’s out there,” said Master Sgt. Paul Allen, a structural maintenance technician at the 173rd Fighter Wing.

One such part is a fairing rib, a semi-circular part originally stamped from a sheet of aluminum with three-dimensional relief. It’s a part that sustains damage in refueling operations when the boom cracks into the aircraft—a somewhat common occurrence—creating an ongoing demand for fairing ribs.

Allen and his structural maintenance co-workers make new ones. First they cover the part with tape, then carefully cut away a section to give them a rough pattern for the new part, and then trace that part on a new piece of metal. Once traced, they cut it from the sheet with hand-tools and file it to match, or as close as they can get. Allen says it’s really not possible to get to .005 of an inch this way—the acceptable tolerance for this part.

Now this flat piece of metal needs to be formed and so they carefully hammer it to shape around a mold. First, they tried a hard plaster cast but it cracked when they hammered the sheet metal against it. They got it done though, as they have for years now—27 man-hours later.

Today, emerging technology can shorten that process to seven hours.

It begins with a better way to assess the parts exact dimensions—enter a brand-new scanning arm with a mounted camera and an attached computer, which can map a part perfectly rendering it in three dimensions. A mold is created using the same software and printed using the brand-new 3-D printer located not five feet away. This printed part takes the place of that wood mold.

“We’re definitely using innovation to save time and money,” says shop supervisor, Master Sgt. Joshua Fuhrer. “If you think about carving a tool from wood, that’s something that goes back to the 1950’s, now we are printing parts in a matter of hours and that’s cutting edge.”

And this mold is very strong, printed from a carbon filament it proves vastly more durable that a wood mold.

The team relies on that strength to utilize another piece of time-saving technology, a “smash-box”. It’s something drill-status Airman Tech. Sgt. Michael Jordan brings to the shop from his experience at Rogue Aerospace Engineering, the company he runs specializing in helicopter repair and part fabrication when he’s not wearing the uniform on drill weekends.

The “smash-box” is a reinforced steel box, lined with a thick rubber mat and closed with a reinforced “lid”, also made of steel. The rubber used is very high durometer and does not easily deform, it’s difficult to make any indentation in it even with, for example, a screwdriver. But when placed in a 100-ton press that same rubber flows around the mold in a nearly fluid state and that shapes the accompanying part perfectly—every  time.

“Being able to reproduce the parts and get the same outcome every time is very valuable,” says Jordan. “For the Air Force, not just the F-15 fleet.”

The reason he says it represents value to the Air Force is because once a part is printed and mapped those files can be transferred to another unit when they need to replace the same part.

Allen envisions a time near at hand when units will share these files frequently creating a platform within the community of Air Force structural maintenance capitalizing on the initial effort being “crowd-sourced” across the fleet and beyond. He goes on to say he doesn’t see a reason why it should be confined to career field or service, and says it may likely be beneficial to the whole of the Department of Defense.