When I restored my Super Cub and first experienced the crystal-clear view through a new windshield, I dedicated myself to ensuring it stayed clean and unscratched. There’s no comparison between the view through a brand-new windshield to the decades-old windshields of the rental aircraft I’ve flown. After thousands of hours of 100-mph dust and insect impacts, those windshields have a permanent haze of scratches. However, much of that damage was not caused by flight conditions, but by poor cleaning practices. When contemplating the cleaning of any windshield, remember the doctor’s maxim, Primum non nocere, a Latin phrase that means, “first, do no harm.”
The fine haze of scratches that characterizes most GA airplane windshields is usually caused by poor cleaning materials, such as paper towels, and poor technique. Many scratches are caused by the very dust and dirt you’re trying to remove. Pilots grind the dirt into their windshield first, before wiping it off.
As a professional photographer, I have some experience keeping expensive optics clean, and I use a similar technique on windshields. Before cleaning a camera lens, the first thing to do is blow off the dust, so you’re not grinding it into the lens with your cleaning cloth and cleaning fluid. If you can avoid getting your greasy fingers on the lens, most lenses never need any cleaning at all except gently blowing the dust off with a squeeze bulb or brushing it away with a very soft brush. Blowing dust off airplane windshields is not practical, however.
The only truly safe way to remove the dust and dirt is to find a hose and use plenty of running water. I stand on a ladder and run the water gently from the top of the windshield to wash away the loose dirt, and then I just let the water keep running. My goal is to rehydrate all those crusty bug carcasses that are stuck to the windshield. Keep the water running and then use your hand or a clean, soft cotton cloth to wipe the surface gently. A cotton T-shirt is good for this, or an old cotton dish towel. All my old kitchen towels and T-shirts go straight to my clean cloth bin in my hangar. Never use a rag with any spot of oil on it.
At first, you’re not using your hand so much for cleaning the surface as to feel how clean it’s becoming. A great percentage of the bugs and dirt will wash away with only the action of the running water. After a couple minutes, you’ll find very few insect parts left. I then use my hand, while continuing the water flow, to pick away at these stubborn remains. It’s just another joy of airplane ownership, picking dead bugs from the windshield with your thumbnail. Once your hand detects no more bits o’ bug, the windshield is clean. Finally, I use a soft, clean cotton cloth—usually an old bath towel—to dry the windshield. This is just to prevent water spots. OK, you’re set to go fly again, most of the time.
Often, this is the end of my cleaning regimen, but after a number of flying hours, an oily film from the engine also coats the windshield, and that doesn’t come off with just water. Now, you have to use a commercial cleaning product.
Most aircraft windows are acrylic plastic, and acrylic scratches readily. So, you must use a cleaner that is approved for this material. However, not all aircraft windows are made of the same plastic, so learn about yours in particular.
Household cleaners, such as Windex or other generic glass cleaners, are deadly to this type of plastic. Remember, it’s not glass you’re cleaning, it’s plastic. Do not use gasoline, alcohol, benzene, acetone, deicing fluids, lacquer thinners, or any other type of solvent that’s laying around the hangar. All these will damage plastics. You have to look through this windshield on every flight, so don’t be cheap about cleaning it, either in time or money.
Clean and/or polish
The majority of spray plastic cleaners on the market also include “polish,” which means wax. For my new windshield, I prefer to just clean it and not use any product with polish. The one I use is Clear View Plastic and Glass Cleaner from Aviation Labs Inc. It foams when applied, removes the oily residue, and dries streak free. Before using any spray-on product, double check that the surface is clean of any dirt or dust, and spray it liberally so there’s a considerable liquid film on the surface. Wipe off the cleaner gently, reapply, and wipe again until the surface is clean and dry. You’ll want to clean the interior side of the windshield too.
After a few years, your windshield can’t help but develop very tiny scratches from the airflow of dust, bugs, and exhaust to the point of being noticeable. This is the time to start using products with polish. They fill the tiniest scratches and will improve the view.
When I was a studio photographer, we used large sheets of Plexiglas for product photography, and on those we used Brillianize, another product specifically made for cleaning plastics. This is one of those “clean and polish” combination products, and it works quite well.
I’ve heard of pilots using furniture polish to clean and polish their windshields. I’ll repeat, use a product specifically made to clean (and polish) plastics. You’re going to be looking through the results of your efforts on every flight.
Some pilots wax their windshields to help the rain bead up and flow away. If you want to use something like this, at least use a product that’s safe for plastics, such as Rain X Plastic Water Repellant.
Aircraft covers are great for protecting your airplane’s interior and avionics from the sun and heat, but make sure they have a soft cloth surface against the windows. Also, they need to be washed often and the covers must be tightly attached. Otherwise the wind will flap the covers and grind any dirt into the windshield for you. The same goes for the heat shields some pilots use on the interior of their airplane’s windows. These shields can be stiff enough, and collect enough dirt, to scratch the plastic windows from the inside.
Do it right or not at all
At my home airport, here in the chilly Northeast, I can’t run the hose on these winter days unless I want to become a human popsicle. Did I mention how I wish our airport managers would install running water in our hangars? I don’t fly as much in the winter and there are fewer bugs to kill, so my windshield is not quite as dirty as during the prime summer flying season. But still, it gets dirty to the point when I’m tempted to clean it, which I absolutely won’t unless I can do it right. I’d rather have it dirty than permanently scratched.
Dennis K. Johnson is a freelance writer and pilot living in New York City.