NewView Technologies Inc. has done numerous classroom presentations at safety seminars in the Midwest to talk about window inspection and care. We are establishing this page on our web site to provide service technicians and quality control inspectors the opportunity to share our knowledge of our experiences found during window inspection, repair, and polishing. Our service is normally called to perform our services to pressurized aircraft usually of a vintage 10 years old or older. The majority of our work is on windows that have age crazing and need restoration for continued airworthiness. This isn’t a new subject to the maintenance side of our industry. Aging aircraft issues have been coming over the horizon for a number of years and the issue will not just “go away” on its own. We hope that you have the opportunity to carry our inspection tips to the work place and make a safer environment for our operators to fly in. FIRST TIP: During a request by our customer we were asked to provide a quote to remove some minor imperfections in the left and right windshields on 1977 Cessna 340. Upon initial inspection we found some cleaning damage from harsh cleaning clothes or perhaps paper toweling, a few very minor chips that measured a maximum of .003” and a few dime sized stripper damaged marks along the center post area. We provided an additional quote to clean the cock-pit side and cabin window exterior surfaces as they all had cleaning damage. Our customer elected to have only the windshields cleaned and polished during the Annual inspection which was planned for within the next 45 days. We had contacted the service center that was planning on the inspection work and made arrangements for a date and time for us to perform the work needed. The day we had arranged for our work to be performed came and we set up our work stands and equipment. We started with the worse of the two windows. Where the cleaning damage was located along the center post area we used an acrylic scrapper to clean back the window sealant for a more open work area for our tools to removed the stripper damage. When the sealant was removed from the center post and windshield surface, we found some new damage under the sealant. We measure the depth of damage and found it to be almost .050” deep. This is beyond limits and well beyond the minimum thickness allowed by the manufacturer. At this point we stopped and red tagged the window and the operator was required to install a new windshield. This is a case of hidden damage from stripper that was caused from the re-paint of the aircraft a few years before. The stripper leached under the sealant and burned into the windshield surface. Left undetected a crack could have grown from the area as the undetected damage measured to 1¾” in length. We’re not suggesting that all window edge sealant be removed at each inspection. We are suggesting that when performing an inspection on older aircraft take a second look at areas that may cause you to be suspicious of hidden damage. With this problem the stripper damage on the windshield being so close to the window edge already indicated that chemicals got under the protective taping during the stripping process during the re-paint. Older aircraft require all of us to perform inspections differently than with late model aircraft. SECOND TIP: Windshield damage on the Cessna 441 Conquest can be hiding on you. During the inspection process an area that can be easily overlooked is just under the hot air discharge duct at the base on the left and right windshields. Hot air from the anti-icing discharge ducting can cause streaking, grooving and heavy crazing to the surface of the windshield exterior. Usually the crazing is hiding and difficult to see as there isn’t enough light under the duct cover to inspect the area correctly. Take a strong lamp and get some light under the ducting to inspect that area. Crazing is often hiding there and can be very deep. Cessna does call out in the maintenance manual that crazing is not acceptable damage on the windshield and must be addressed for continued airworthiness. We were able to notify a customer of this hidden damage and he wasn’t able to save the windshield because the crazing had been left alone for too long of a period. The sooner crazing is repaired, the better. The owner of this aircraft told me, “All conquests have that damage in the same place”. If you have questions about what crazing looks like or where it comes from, please give us a call and we can talk you though what to look for and how to treat the damage. |
