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The 737's rear exit doors cannot be used to evacuate the aircraft in the event of a water landing, as shown, for example, in this safety card:

737 safety card

(Image from flight-report, via Jordy here at AvSE.)

In contrast, the rear doors on (for instance) the A320 series can be used for a water evacuation:

A319 safety card

(Image by Czechnology here at AvSE.)

Why can't the 737's rear doors be used during a water landing?

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    $\begingroup$ I like the optimism of these "safety cards" showing a pristine aircraft floating nicely on the water after a ditching. Statistically unlikely but makes for a pleasant looking card. $\endgroup$
    – Ron Beyer
    Commented Apr 4, 2019 at 2:55
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    $\begingroup$ There was that time a guy with a lot of glider experience landed an airliner in the Hudson River a few years back, after the engines died right after he took off from the airport. $\endgroup$
    – nick012000
    Commented Apr 4, 2019 at 3:55
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    $\begingroup$ Yeah, and they couldn't use the rear doors. Know why? They were underwater... This was an A320. $\endgroup$
    – Harper - Reinstate Monica
    Commented Apr 4, 2019 at 4:00
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    $\begingroup$ @nick012000 and they call it "The Miracle on the Hudson" for a reason. $\endgroup$
    – Arcanist Lupus
    Commented Apr 4, 2019 at 6:02
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    $\begingroup$ Looks like Airbus tell you to check, but Boeing reckon it's not even worth checking. In the one photo I can find of a successful Airbus landing on water, you wouldn't open the rear doors anyway... home.bt.com/images/… $\endgroup$
    – Jason
    Commented Apr 4, 2019 at 7:13

2 Answers 2

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The bottom of the door opening sits too close to, or below, the water line when the airplane is floating.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Jamiec ♦
    Commented Apr 5, 2019 at 12:37
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It all goes back to how the aircraft is designed; the ways different planes float vary. when the 737 ditches on water the tail-section of the plane is deeper in the water than front of it, because the wings are a huge floating point and support most of the weight of the aircraft when afloat, and the bigger front of the airplane contains more air so when floating it will be lighter hence pitching the nose up, causing the tail and the rear doors to be below or very close to the water. this is why these doors remain shut in the event of evacuating after an emergency water landing so that water doesn't get in any faster, giving the plane and its passengers and the crew more time to evacuate and stay afloat longer until help arrives.

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    $\begingroup$ "[T]he bigger front of the airplane contains more air so when floating it will be lighter" and, by the same argument, a big empty box weighs less than a small empty box because it contains more air! You've forgotten that the bigger container also has bigger walls, which weigh more. $\endgroup$
    – David Richerby
    Commented Apr 4, 2019 at 10:23
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    $\begingroup$ @DavidRicherby You're forgetting the square-cube law. $\endgroup$
    – Katastic Voyage
    Commented Apr 4, 2019 at 12:03
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    $\begingroup$ @DavidRicherby - Yes, bigger empty boxes weight less than smaller empty boxes when both are submerged in water. $\endgroup$
    – Pere
    Commented Apr 4, 2019 at 15:18
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    $\begingroup$ @DavidRicherby You are the one introducing the interpretation of "lighter" in the answer as meaning less weight rather than more buoyancy. The answer did not say the former, and clearly meant the latter. If you really want to nitpick, it is the wording, not the concept. $\endgroup$
    – Backgammon
    Commented Apr 4, 2019 at 17:12
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    $\begingroup$ @DavidRicherby, the tail is a pointy cone with a bunch of thin bits of metal sticking off of it. It's got a lot of metal and only a little air. The nose is a rounded object containing a whole lot of air and only a little metal. It's not surprising that the nose floats higher than the tail. $\endgroup$
    – Mark
    Commented Apr 4, 2019 at 22:17

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