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When you’re driving on the highway, after sometime unwanted insects and dirt accumulate on your windshield. When you stop over at a gas station, you might clean it off. It’s likely the case for aircraft as well, especially during takeoff and landing. But how frequently are airplane windshields cleaned? And how are they cleaned? Does this include cleaning of passenger windows?

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    $\begingroup$ Are you interested specifically in commercial operations, or are you wondering about GA as well? $\endgroup$ – Ron Beyer Jun 17 '18 at 16:08
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    $\begingroup$ Related: aviation.stackexchange.com/questions/25881/… $\endgroup$ – kepler22b Jun 17 '18 at 16:34
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    $\begingroup$ @RonBeyer commercial, but now I’m wondering about GA too $\endgroup$ – TayE Jun 17 '18 at 16:44
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    $\begingroup$ @PrashantSaraswat There is no requirement to clean GA windows before every flight, in fact you shouldn't clean them (just verify that they are clean). Excessive cleaning causes crazing/hazing. None of the checklists on the 177 I own, nor the 172 I learned in had "clean windows" as part of the preflight checklist, it may be something your school/rental company has on their checklist. $\endgroup$ – Ron Beyer Jun 17 '18 at 19:17
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    $\begingroup$ @PrashantSaraswat you said "you are supposed to clean the windows before every flight. This is part of the checklist". That's very different from saying it's something you do before every flight and is a part of your checklist, and sounds very much like you're saying it's a legal/FAA requirement or standard manufacturer recommendation. $\endgroup$ – Chris H Jun 18 '18 at 7:01
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I clean them whenever they are dirty to the point of affecting ability to see traffic or cause distractions.

Bugs, dust, and dirt can make it very difficult to spot traffic, birds, and obstructions, especially in hazy weather.

It is the pilot’s responsibility to “see and avoid” and clean windows play a large role in this critical safety area.

Depending on how bad contaminants are (i.e., if it’s bug season) the interval for cleaning could be as often as every flight or as little as once every few days while continuous flight operations are in effect.

Windows are cleaned with either water or special chemicals for cleaning plexiglass with microfiber or non-abrasive cloths. Also of note, human fingerprints are ideal for cleaning aircraft windows with water as they are soft and do not scratch, but the ridges pick up the dirt and easily rub off even sticky contaminants [bugs]. Aircraft windows are relatively soft and scratch very easily. All cleaning motions are done in the direction of the airflow to prevent hazing of the window from scratches... no circular scrubbing - only in the direction of air flow. Passenger windows rarely get dirty. It’s the ones for the cockpit that are directly exposed to the frontal airflow that get the worst of it.

I usually use water, my fingerprints for scrubbing, and clean microfiber cloths for drying to prevent water spots - which can obscure vision as bad as dirt.

Here is a video of the process.

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    $\begingroup$ I strongly second the water/hand method for initial cleaning of plexi. Any windshield will have some coating of "dust" which is actually mostly silica particles along with pollen. If you just take a cloth with Mirror Glaze or some other product without a water/hand rinse first, you are literally sanding the plexi. A great product for cleaning and polishing after the initial water cleaning is Lemon Pledge. The lemon helps break down bugs and it doesn't streak. $\endgroup$ – John K Jun 17 '18 at 22:30
  • $\begingroup$ I think you meant fingertips, unless you keep a baggie filled with fingerprints and sprinkle them on the window along with the water. :-) $\endgroup$ – grumpy1arrival Jun 20 '18 at 3:57
  • $\begingroup$ @grumpy1arrival lol, yes I did - but it doesn’t get the point across as to why fingertips are better than a scrub brush as well as saying fingerprints does :-) $\endgroup$ – Pugz Jun 20 '18 at 4:12
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    $\begingroup$ @TayE looks like nobody ever taught him how to clean an airplane windshield :-) sadly, it exists at all levels. $\endgroup$ – Pugz Jun 22 '18 at 14:32
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    $\begingroup$ @TayE I’m just being a pain. Modern jet airliner windows are made up of layers of glass, plastics, and laminates, as well as often several conductive electrical layers. This is very different from a traditional aircraft window made of just plexiglass... they must withstand the temperature of the de-icing system and also bird impacts at hundreds of knots. Either way, good practice is good practice... airflow and particles in the air always flow in the direction of airflow and it’s good not to clean against the grain. $\endgroup$ – Pugz Jun 22 '18 at 14:36
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Although this is a small subset of aviation, at the seaplane base I worked at, windows were cleaned every morning and potentially multiple times a day if salty spray got on them. It’s the pilot’s discretion, but most pilots I know prefer a clean windscreen.

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