Airframe Technology: Scratches and Dings

West Star Aviation provides tips on how to repair aircraft windows

In concept, aircraft windows are just like the windows in your house. Both are designed to provide light, protect you from the elements, and let you see what is going on in the great outdoors. To function well both need to be clean, free of dings and cracks, and sealed properly.  That said, aircraft windows make a radical departure and are a conundrum. Aircraft windows are some of the strongest parts of the fuselage. Many aircraft have “Cut Here In Case of Emergency” stenciled on the outside of the fuselage vs. “Break Window in Case of Emergency.”  

Windows get their strength from their design, construction methods, and materials. Modern aircraft cabin windows are usually made of two layers of acrylic for thermal insulation and a clear view. The outer pain shields passengers from the very cold high altitude air and the inner pane keeps humidity from condensing and frosting.

Cockpit windows are stronger and more complicated. They are made of multiple layers of high-impact glass or stretched layers of acrylic, heating elements, and mounting hardware. The structural members of the window are usually designed to withstand 1.5 times the normal operating pressure. These windows must provide the flight crew a clear view, remain ice free, shed rain, and withstand bird, lightening, hail, and runway FOD strikes. They do this well. Make an Internet search and you’ll find cases where aircraft windows have sustained incredible hail damage.

I had the opportunity to work on a Boeing 707 that ran into a barrage of large hail stones over west Texas. The hail caused severe damage to cockpit windows, all leading edges, engine nacelles, pitots, and destroyed the radome. The cockpit windows took a severe beating but held and the crew was able to make an emergency landing at Dyess Air Force Base in Abilene, TX.

In this strength lies the conundrum. While aircraft windows are strong, they are fragile and can be damaged if not handled with care. They are also the quintessential high maintenance items.  Servicing and maintaining expensive aircraft cockpit and cabin windows are challenges for the experts and a sand trap for the inexperienced. AMTs who are working hubs, line stations or local FBOs know that our pilots are very particular about their windows. Passengers also complain when their windows are dirty or crazed. Windows are key signature features and functional components of the aircraft; however, in normal operations, accidents do happen, windows crack, get scratched, craze, and yellow with age. They must be serviced, have damaged repaired, or if the damage is beyond limits, replaced. One of the challenges for owners and operators is to determine when to repair or replace the window.

West Star Aviation

There are many service companies that can assist with this determination and then make subsequent repairs or replacements. One of these is West Star Aviation Aircraft Window Repair and Refinishing located in Grand Junction, CO. West Star Aviation offers aircraft service for most corporate aircraft including Falcon, Hawker, Citation, Challenger, Learjet, Conquest, King Air, Conquest, Embraer, and Westwind. It will repair, refinish, or replace cockpit and cabin windows at the Grand Junction facilities or travel to most customer locations. Determining when to repair or to replace your window is no small decision due to cost and downtime of the airplane.

However, once the decision has been made, according to Dave Krogman, general manager of West Star, “Repairing windows typically results in a 90 percent savings over replacement.”

Do-it-yourself evaluation service

West Star Aviation offers customers about $7,000 of specialized window inspection equipment that includes a digital optical micrometer, inspection light, camera, forms, and inspection criteria. It ships the tools to you free so the client can measure damage and window thickness. The typical cockpit window damage customers call about is pitting from runway FOD and crazing. With cabin windows, the damage is usually scratches from headsets, clip boards, finger rings, watches, and other sharp objects passengers bring onboard.

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