A Clear Outlook

Repair tips from Aircraft Window Repairs' Bob Cupery


My first aircraft window job was to resurface several cabin windows on a Boeing 707. Repairing and polishing aircraft is a delicate, multi-step, monotonous job. We started the process with soft rubber sanding block and 2000 grit paper, with strict instructions from the crew chief to make vertical sanding strokes only.

For those that have done this job you know 2000 grit paper is about as abrasive as cigarette smoke and takes ages to make much progress. After about three hours of sanding my teammate decided that an orbital pneumatic sander with a felt pad and some buffing compound would be a better choice for this job. He applied the sander to the window and after a few quick revolutions; the window turned a white opaque color and glazed rock hard. The end result was the window had to be replaced, and my teammate incurred the wrath of the old crew chief.

If you surveyed the OEMs, the back shops for the airlines, and the window repair companies, you would find that servicing, repairing and replacing aircraft windows is big business. There is a lot of tribal knowledge and expert craftsmanship associated with repairing aircraft windows. Bob Cupery, founder and current CFO and QA manager for Aircraft Window Repairs of Torrance, CA, is the guru of repairing aircraft windows.

Aircraft Window Repairs

Cupery is one of us and a great American success story. He was an AMT for Northwest Airlines and maintenance director for Northrop, and listed in Who’s Who in America Industry and Finance. Bob started business in his garage and it became the first FAA certified repair station solely dedicated to the repair of acrylic windows and lenses for pressurized aircraft. Cupery and his wife Kathi have been in the business for about 32 years. I asked him to pass along some of his window repair expertise with a focus on window maintenance and the different types of damage that AMTs should look for. He agreed and provided an abundance of valuable information.

Windows surround us; they literally are part of almost every structure built to move or shelter people, cars, boats, buildings, and aircraft. We rarely notice them until we can’t see through them. In fact, windows are so much a part of our lives we often think they are all alike. However, when we as AMTs start treating all windows the same we’re asking for trouble. For one thing, not all windows are made of glass. With few exceptions, aircraft windows are formed from stretched acrylic which provides a relative inexpensive, tough, shatter proof transparency ideal for use on airplanes. What’s more (and something many people forget)on some aircraft windows are primary structures carrying the same loads as the metal fuselage.

Cleaning and care

Acrylic aircraft transparencies require careful treatment and protection. They also discolor with age. Even with a conscientious maintenance program, you may still notice some yellowing or milk-coloring. Such color cannot be removed without weakening the acrylic and eventually you’ll have to retire those old panels. However, you can extend the life of aircraft windows by following a few suggestions.

First, never use an ammonia-based glass cleaner on acrylic windows. Ammonia may be great for glass, but it’s hard on plastic. Even approved plastic cleaners in aerosol applicators should be avoided. While the cleaning agent is safe, the majority of aerosol chemicals can damage acrylic.

To clean a pane properly, apply an approved plastic cleaning agent to the windows. Each time you wipe across the window use a clean side of the towel on each pass; this will remove the abrasives and safely buff the window. You’ll use a few more paper towels and cleaner but that costs a lot less than having to refinish your windows or purchase new ones.

When it come to inspections Cupery recommends that an AMT be very diligent and always make a careful, detailed inspection of all windows. Always, remember certain window conditions and minor damage can accelerate to a condition that requires an expensive replacement.

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