I was watching the startup sequence for an A320 and it struck me as unnecessary minutiae to ensure the wipers are off before power on. Is there something important that I'm missing that puts windshield wipers in the same list as thrust and gear levers?
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$\begingroup$ Cant depart the gate if you cant see where you are going - not as relevant on a sunny day, but its in the checklist for that reason. $\endgroup$– MooCommented Jul 22, 2016 at 17:58
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1$\begingroup$ @Moo makes sense, but the power-on checklist is to ensure the wipers are in the off position before starting the APU. I clarified the Q a bit. $\endgroup$– joshperryCommented Jul 22, 2016 at 18:03
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3$\begingroup$ Related: Aircraft ice and rain protection. They must be off, in their park position, to prevent damages due to a dry windshield. Repellent on a dry windshield is also a problem. On the other hand I believe they must be operational for landing on Cat II or III. $\endgroup$– minsCommented Jul 22, 2016 at 18:14
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$\begingroup$ Wouldn't it also make sense to check that they are operational? $\endgroup$– Simon RichterCommented Jul 23, 2016 at 15:01
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$\begingroup$ @SimonRichter it would... Asking about that would make a great new question. $\endgroup$– FreeManCommented Sep 7, 2017 at 11:52
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1 Answer
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For the same reason you should turn your wipers off when you shut off your car (since very few people go through a power-up checklist in their car...):
Running the wipers on a dry windshield can damage both the wiper and the windshield as the dry blades drag small particles of dirt, grit, rocks, etc across the windshield. These particles can tear up the rubber of the wiper, and they can scratch the windshield. Dragging dirt and rock particles across a wet windshield isn't inherently good for either wiper or screen, but the water acts as a lubricant and significantly reduces the damage potential.
It's far cheaper to print an extra line in the check list and have the pilots take 5 seconds to check it than it is to replace wiper blades and windscreens.
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6$\begingroup$ Sounds a little like the reasoning behind me always giving the gear stick a sideways nudge before releasing the clutch in my manual transmission car when the car is standing still: It takes next to no time and greatly reduces the risk of costly damage to the equipment (the car's transmission, in that case). Finagle's Law applies: the one time you don't do it, you can rest assured that it will be the one time it's in the wrong position, and you get that "oh, crap" wakeup call. $\endgroup$– userCommented Jul 22, 2016 at 21:14
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$\begingroup$ Great answer, thank you. Definitely makes a lot of sense, especially considering what an FAA certificated wiper blade and windshield must cost! $\endgroup$ Commented Jul 22, 2016 at 21:39
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$\begingroup$ +1 on driving a stick, @MichaelKjörling! I do too, and it took a lot of hunting to find a decent one! We now return to our regularly schedule airline programming $\endgroup$– FreeManCommented Jul 23, 2016 at 0:54
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$\begingroup$ @user I've driven a car with a manual transmission for years and I've never heard of that one. What is the point of nudging the stick? $\endgroup$ Commented May 17, 2021 at 17:04
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1$\begingroup$ Thanks @FreeMan, that makes sense. I thought he or she was talking about getting the car rolling after being stopped. BTW I don't wiggle the stick before taking my foot off the clutch when I think I'm in neutral, and I have lurched the car a few times over the years, so perhaps I should adopt that helpful habit. $\endgroup$ Commented May 17, 2021 at 17:46