A collection of aircraft parts available for NDI research
By Barb Zuehlke
A lending library of aircraft parts? Yes, the Structures Laboratory of the Institute for Aerospace Research, part of the National Research Council Canada, based in Ottawa, has developed a collection of more than 700 aircraft parts for use in aging aircraft and nondestructive inspections (NDI) research.
The Institute for Aerospace Research (IAR) conducts research on issues related to the design, performance, use, and safety of aircraft. The institute performs research and product development studies with an eye on the OEM, maintenance, and the airworthiness authority (TC, CAA, or FAA). R&D includes teardown and experimental investigations, NDI, computational and experimental analysis technologies, life enhancement technologies and repair, and proactive maintenance practices. The Structures group performs materials properties tests on coupons, built-up structures, and full-scale tests: currently a F-18 wing test. It has developed enhanced visual inspection techniques for aerospace and forensic applications, and has created a library of parts to support its research, the Aircraft Specimen Library (ASL).
The library collection was driven by IAR's early work on D Sight™, a technology adapted to detect barely visible impact damage on composites. It was thought at the time that D Sight would also be good for detecting corrosion pillowing on metallic construction. That led to a discussion of whether to build specimens to support the experiments. "We quickly realized that there are so many changes in construction throughout the aircraft that it would be a nightmare to manufacture exact replicas," says Ron Gould, IAR technical officer and the ASL custodian. The need for specimens for research started as a small collection to support one program and from there grew into a library supporting many programs.
Starting the collection
Ron Gould and his partner Jerzy Komorowski, now the director of the Structures, Materials, and Propulsion Laboratory, went off into the desert and started collecting pieces. The first specimens collected were small and "all fit in a box that we carried home." Since that start in 1993, IAR has collected more than 700 fuselage and wing pieces from more than 50 aircraft, both civilian and military. Most specimens are 10 square feet or more in size but the largest piece is the "Aging Aircraft NDI/Maintenance Test-bed Vehicle" a complete Boeing 727-90C which is being used for corrosion and aging wiring studies.
The collection includes both corroded and noncorroded structures from withdrawn-from-use aircraft. In situations where naturally corroded specimens have not yet been collected, IAR disassembles and selectively removes the protective coatings in the joints of undamaged specimens, reassembles them and, through a salt fog exposure program, studies corrosion from the onset. Careful protective packaging ensures that only the targeted surface is exposed to the corrosive environment.
"That's the kind of thing we offer through the library," Gould says. "We supply a number of external labs and internal projects that have a specific construction they want to interrogate or develop a technique on. If we don't have an example of a naturally corroded structure in the library or can't find it in the bone yards, we will grow it. We've gone to the expense of chemically analyzing the corrosion product that results and comparing it to what we find in the naturally corroded joints to prove that we do produce the same results."
There is no charge to borrow specimens, just the shipping costs that are incurred. While the initial goal was to have the parts available for internal projects, they can also be borrowed or purchased.
"Any piece in the library has value added to it," Gould says, "because we've done the nondestructive inspections to quantify the damage. In those cases where we've sold pieces, we charge for that added value. When we loan specimens for, say, the development of laser ultrasonics, we ask that the data collected be added to our NDI database."
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