Going in reverse

  • Published
  • By Mike W. Ray
  • Staff Writer
Tinker AFB Engineering has many tasks, ranging from equipment and building management to fixture and tool design. Typically when Engineering receives a request for parts or tooling, aircraft drawings (mylar) are used to design the needed item that eventually is made in one of Tinker's machine or sheet metal fabrication shops.

However, the 76th Commodities Maintenance Group has a six-member reverse-engineering group that does it the other way around. As the Air Force's fleet of aircraft ages, replacement parts and engineering information become scarcer. The Engineering group now must create aircraft parts or tooling from existing parts, instead of being able to use detailed aircraft drawings.

This technique is accomplished by scanning with computerized equipment to create a three- dimensional model of the part, which then enables Tinker's machine or sheet metal fabrication shops to create new, identical, copies of that part. Sometimes a Tinker mechanic will have some, but not all, of the drawings needed to replicate a part or tool, resulting in a visit to the reverse engineering unit to have the object scanned, 76th CMXG mechanical engineer Todd Bayles said.

"We scan the part and collect three-dimensional data," said Nathan Pitcovich, also a 76th CMXG mechanical engineer. Their tools of the trade are a Leica laser tracker and an ATOS white light scanner.

Utilizing lasers, the Leica can scan millions of points on an object, while the ATOS system uses photography to construct a digital replica of the part. The Leica can do "a wide scope of things," and can scan objects as large as 30 to 40 feet long or small detailed parts the size of a coffee cup, Mr. Pitcovich said. In contrast, the ATOS is best for use on "large, relatively smooth parts," Mr. Bayles said.

There are perhaps 20 to 30 models of scanners on the market that provide "a different degree of accuracy," Mr. Pitcovich said. "Ours are among the most accurate." The scanners used by Tinker's reverse engineering group are accurate to less than 1-1,000th of an inch, he said.

The Engineering section can use the equipment to scan and fabricate needed aircraft parts; they also can save large amounts of money manufacturing expensive replacement parts for their equipment when something breaks. Recently they were able to make a new section of a fuel transfer boom because a particular piece of the exterior skin was needed, and they reverse-engineered a broken impeller (rotor) for one of their high pressure pumps in the shop.

Just recently they were contacted by Vance AFB, which had one ejection-seat cart and needed more but had no drawings of the cart. "We scanned the one they did have, found its dimensions and made the design drawings," Mr. Pitcovich said. "Now they can make as many as they need."

"Typically, we need only one or two of the parts we scan" Mr. Bayles said. If mechanics need large numbers of parts, "They will usually go to the manufacturer if possible."
There is another, less obvious, benefit of reverse engineering, Mr. Pitcovich said.
Previously when Tinker AFB purchased an aircraft part from a vendor, "We didn't have a way to verify the accuracy of the entire part," he said. "Now we can scan the purchased part and compare it against our CAD model, and determine whether the replacement part has been manufactured to the correct tolerances."

Similarly, sometimes they're visited by a mechanic who says, "This part isn't working. Can you find out why?" The reverse engineering group scans the part, compares the computerized, 3-D scan against the original plans and specifications, and determines where the problem lies.

The work is sporadic, perhaps three or four aircraft parts per month, Mr. Pitcovich said. However, requests for their services are picking up "as more people hear that we have this capability."