Live accounts of survivors of Bangla Air 211 mention getting out after breaking windows but not out of the emergency exits.
My question is can regular airline exits not work in such cases?
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3$\begingroup$ As a rule of thumb, if you see more than one copy of something that serve the same function in a system, that thing is usually known to the designer of the system to fail more often than they really want. $\endgroup$– user3528438Commented Mar 22, 2018 at 16:51
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9$\begingroup$ @user3528438 You're suggesting that there being more than one emergency exit means that emergency exits fail too often? It has a heck of a lot to do with needing to get a lot of people out the plane quickly, and that means multiple doors. $\endgroup$– David RicherbyCommented Mar 22, 2018 at 19:59
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8$\begingroup$ @DavidRicherby And also with crashes tending to result in situations where some exits may be particularly undesirable places to leave the aircraft (e.g. a fire, running jet engine, or fuel spill on one side or a water landing where the back of the aircraft is submerged.) There's a reason that the certification requirements require that the passengers have to be evacuated in the test using only half of the doors (and exactly which ones those will be are not told to them ahead of time.) $\endgroup$– reirabCommented Mar 22, 2018 at 20:03
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7$\begingroup$ @user3528438 your rule of thumb is sorely misguided. $\endgroup$– FedericoCommented Mar 22, 2018 at 20:55
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3$\begingroup$ @user3528438 There are other reasons to make multiple copies of something. For instance, many planes have more than one wheel on each landing gear, but the rationale is not due to the failure rate of wheels. It's for weight distribution. I think that if you amended your rule of thumb to include the word "redundant," it would be more likely true. $\endgroup$– Cort AmmonCommented Mar 22, 2018 at 22:50
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2 Answers
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All regular exits are generally used in an emergency. This information would be included on the safety card and in the briefing by the crew before the flight.
Of course, during a crash, structure can deform and exits can become blocked. Regulations require evacuation within time limits using only half of the available exits. This must be demonstrated to be possible.
Here is a Q400 safety card, showing that two forward and two aft exits are used for evacuation. The forward right exit (called R1) is an emergency exit.
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11$\begingroup$ Note the instructions on that safety card to look out the exit's window first and not to use it if you see fire or debris in the way. $\endgroup$ Commented Mar 22, 2018 at 17:08
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Well the short answer is, it depends. As already noted in a comment, an aircraft’s structural integrity can be jeapordized in the event of a crash landing. This primarily comes down to the impact itself. How powerful was it? What forces acted upon impact? Did these forces impact the emergency exit or its frame? Emergency exits, just like any part of an aircraft, are not indestructible; even a block box can be severely damaged due to some impacts for that matter. With that said, let’s say the aircraft in this scenario has 6 emergency exits. If the first three do not open after a crash landing, it doesn’t necessarily mean the other three won’t. Think of it similarly to a car accident. Whether or not the doors open after the impact relies solely on whether or not the door itself, the door jam, or the mechanism opening the door were damaged enough for it to not open due to the force of the crash and whether or not those forces acted upon any of these factors. Like an aircraft, just because the driver door in a car doesn’t open in a particular accident doesn’t mean the passenger door won’t and vice versa.
