A large vacuum return hose is also used inside the fuel cell. It has a 400-cfm waste collection and filtration stage that removes ablated sealant debris and related vapors, keeping the working surface clean. After all, this is a fuel cell we are working in!
When it comes to sealant removal, the only difference between the 200- and 500-watt laser systems was how long the job took. Either way, the laser beam completely removed sealant measuring about 1/8 inch in depth from the nut fasteners. Again, the photos tell the tale: The fasteners were left clean and accessible without suffering any damage.
“We did the test with inexperienced operators, to provide useful results to MROs and other potential users,” Olson says. “The only variable they had to master was to keep the beam’s focal length within a range of plus or minus 3/16 inch for maximum efficiency, which each did after a little practice. The only safety requirement was protective clear eyeglasses. These glasses filter out the laser light without obstructing the technician’s vision.”
When compared to mechanical sealant removal techniques, laser removal is faster, more effective, and safer to the aircraft and the technician. The equipment is also durable. For instance, the 200-watt system has been used in GLC demos since 2000 without laser-induced damage. That’s about 3,000 cumulative hours. Meanwhile, the newer 500-watt laser system uses laser diodes that are warranted for 10,000 hours of operation.
So what’s the downside? Cost. “Using a laser works out to about $1,000 per watt in terms of equipment,” says Olson. “This means that a one-off (non-volume sales) 200-watt laser system will cost you $200,000, and a one-off 500-watt system will cost about half a million.”
To date, this cost has kept the laser removal system off maintenance shop floors. That’s a shame, because such equipment could pay for itself very quickly. For the A-10 Warthog requirement, cost savings could pay for a system after less than 10 aircraft, and that does not count the benefit of a much faster maintenance throughput.
So what’s the solution? One idea would be for MROs in a given region to band together to purchase and then share a laser removal system. Another idea would be to establish third-party laser removal companies, who would travel from MRO to MRO as required to provide a coating removal service, or as needed to rent the equipment for the MRO to use.
“Laser removal works; there’s just no doubt about it,” Olson concludes. “Now we just have to find a way to get it into the market, and into aircraft repair shops.”
"Gee Whiz" Technology Part II By Fred Workley October 1998 Fred Workley is the president of Workley Aircraft and Maintenance Inc. and director of Aircraft Appraisals at...
"Purge Air" aircraft fuel tank rapid purging and venting system can be used to quickly drain residual fuel in tanks, purge and ventilate the tanks, and provide technicians with a supply of...