I recently flew on a Boeing 737-800 and found these arrow markings on the wing. What are they for?
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71$\begingroup$ These tell the air which way to go over the wing. - If the air goes the wrong way it makes the ride bumpy. $\endgroup$– A. I. BreveleriJan 2, 2018 at 6:39
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$\begingroup$ I love that this comment has 2x the upvotes of the correct answer! $\endgroup$– acpilotJan 14, 2018 at 1:48
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2 Answers
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They are the overwing exit markings. You can see them in full in the following photo.
Boeing 737 Max overwing exits. By Oleg V. Belyakov - http://spotters.net.ua/file/?id=110706&size=large, CC BY-SA 3.0, Linkec
This is because as already noted in another answer, B737 does not have self inflating slides for its overwing exits and as such, the passengers need some guidance for exiting, to prevent them from going the wrong way.
The above image shows the procedure for using the overwing exit.
answered Jan 2, 2018 at 4:19
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4$\begingroup$ +1, but I'd add the following to make this answer 100% complete for my taste: (just nitpicking from the labels in the question) This is not really a feature related to the aircraft itself (Boeing 737-800), but a feature of the livery (the paintwork) put there by the operating company. The only requirement is that they must have emergency exits over the wings. E.g. I have seen these on A319 and A320 from companies like EasyJet and AerLingus $\endgroup$ Jan 2, 2018 at 10:04
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They direct people who've used the over-wing emergency exits to proceed to the back of the wing, where the flaps are (hopefully) extended, giving them something to slide down to get to the ground. The leading edge would be a much harder trip down, AND if the engine is still running, you're about to run forward into the area where you're at risk of being sucked into the running engine. If you went aft and get caught in the jet-blast, you may tumble, but that's better than hitting the spinning fan blades!
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1$\begingroup$ If one engine is still running you're unlikely to be disembarked on that side so that comment seems erroneous. Never heard of an evaluation with all engines running. Also the air flow out the back of an idling engine is still hot and powerful, I'd rather not get in its way. $\endgroup$– Notts90Jan 2, 2018 at 21:05
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1$\begingroup$ @Notts90 There are many reasons you might need to evacuate, many of which have nothing to do with an emergency engine shutdown. From inside the cabin, one's ability to determine if a particular engine is or isn't running is a little limited - especially with smoke & panic in the cabin.The reason you don't hear of many evacuations with engines running is, it's a bad thing & pilots will try to get engines shut down before ordering the evacuation. But that's not certain to happen 100% of the time. Yes, jet blast is unpleasant, but far more survivable than going into the fan blades! $\endgroup$– Ralph J ♦Jan 2, 2018 at 22:02
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1$\begingroup$ A powered down airplane is a lot quieter than you'd think, simply because a powered-up airplane is so loud. Hard to experience the spookyquiet unless you're on a train when the power/HVAC goes out. $\endgroup$ Jan 2, 2018 at 23:45
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1$\begingroup$ There have indeed been emergency landings where it's been impossible to shut down an engine (QF32 for example), nor can you usually see the engines from the cockpit if the instruments aren't accurate. In QF32's case, there was no need for an emergency evacuation, but had there been a serious fire on board there would have been no option other than to evac passengers with or without the engines safely shut down. $\endgroup$ Jan 3, 2018 at 17:33