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There are some people say the brace position was invented so that passengers don't experience pain when they die in a crash. The brace is designed so that you die quicker (by breaking your neck).

One source: Here

Is that true? If not, how does it provide better protection during a crash?

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  • $\begingroup$ It is more difficult to get hit by an object if your head is down. $\endgroup$ – Trebia Project. Dec 19 '17 at 9:56
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    $\begingroup$ The source you've linked is tagged as "conspiracy theory" and I believe it is for good reason. Please search/read other resources as well, seems statistical evidence tells otherwise. $\endgroup$ – gusto2 Dec 19 '17 at 12:52
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There are a number of reasons the brace position is recommended.

  1. (apologies if graphic) If, in an emergency landing there are a number of jolts or a hard stop of the aircraft, think of kinetics - if your head is thrown forward about a metre with your hips restrained by the belt, that's going to whack your head against something at high speed, and cause more force on your seatbelt, causing (possibly) internal injuries. If you are already in that position, you may find yourself moving maybe 10cm at most. A big difference.
  2. If your head is below the top of the seat, then if the overhead lockers should fall, then you wont be bashed on the head.
  3. It does protect you also from loose flying objects which at that speed become missiles.
  4. Your head is below the window level in case of any shattering windows.
  5. every airline is different, so follow their guidelines as the design of their seat and belt may differ to others.
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  • $\begingroup$ #1 doesn't make any sense. You're going 200mph when you hit the ground regardless. It doesn't matter if you move 10cm or 10m before you hit whatever it is that stops you, the sudden stop is the same. You're still going from 200mph to 0mph in a short period of time. $\endgroup$ – Nuclear Hoagie Dec 19 '17 at 15:09
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    $\begingroup$ I edited your first bullet to make physical sense, since both you and your frame of reference are traveling at the same speed. The issue (as you point out) is that your head moves farther during a sudden stop if you are not braced/bent over, hence greater chance for grevious injury due to higher kinetic energy at impact. Edit again if you want; to use your own words. $\endgroup$ – KorvinStarmast Dec 19 '17 at 18:06
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    $\begingroup$ @NuclearWang #1 actually makes a lot of sense, but it might be clear to say "the brace position is to stop whiplash" of the passengers neck/spine. "When performed properly, the brace position reduces injury to the head, neck, and legs. It also helps prevent whiplash", from: theflightexpert.com/how-to-survive-a-plane-crash $\endgroup$ – Penguin Dec 20 '17 at 8:15
  • $\begingroup$ "Your head is below the window level" Are you sure? It doesn't look significant, if indeed the case at all (depends on type), to me. See e.g. alamy.com/stock-photo/aircraft-cabin.html and en.wikipedia.org/wiki/File:Lufthansa_737_interior.jpg and commons.wikimedia.org/wiki/… and commons.wikimedia.org/wiki/… and commons.wikimedia.org/wiki/… and commons.wikimedia.org/wiki/File:A380_Economy_seats.jpg. $\endgroup$ – user Dec 20 '17 at 9:20
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    $\begingroup$ @NuclearWang: none of the safety measures pertain a full crash. They are useful is smaller, survivable, accidents. $\endgroup$ – Martin Argerami Feb 9 '18 at 0:54
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The FAA has a study on it you can find here the study is worth reading completely but the important parts of the conclusion seem to be,

Current Brace Position

This position (head against the seat back, hands on top of the seat back) was evaluated for three common types of seat backs.

current brace position

This position was only successful for locked-out type seat backs. For full break-over and energy absorbing type seat backs, the ATD’s arms pushed the seat back away, allowing the head to accelerate relative to the seat back, increasing the severity of the head impact. There was, however, no evidence that the ATD interaction with any of the seatback types resulted in hyper-extension of the shoulder joint.

Lower leg forwardlower leg vertical

The “Forward” and “Vertical” leg brace positions permitted the lower legs to flail forward and contact the seat in front. This contact produced femur bending and compression (below criteria limits), and tibia injury risk in some cases.

lower leg aft

The “Aft” leg brace position reduced lower leg flailing and prevented femur contact with the front of the seat frame. This position resulted in low femur and tibia injury assessment values; however, it is only achievable for occupants whose lower legs are long enough for their feet to firmly touch the floor.

Alternate Brace Position

To reduce the detrimental interaction between the occupant’s arms and the seatback, the current position was modified by placing the hands down by the lower legs instead of on the seat back.

alternate brace position

This “Alternate” position was successful in reducing head and neck injury risk for all of the seat back types evaluated.

Pike Position

This position is currently recommended when the seat in front is too far away to support the head, or there is no seat in front, as in a bulkhead row.

pike position behind wall

It was successful in reducing head and neck injury risk in the row-to-row scenario, as long as the struck seat back has a relatively soft local compliance at the point of impact. When seated behind a bulkhead, the effectiveness of the pike position was dependent on whether the head of the occupant struck the bulkhead. “Head-path-reducing features,” such as Y-belts, prevented head contact at the typical 35-in setback.

So the answer is really, it depends on the position as well as the seats in question. You find a full explanation of what the various seat types are on page 2 of the study.

Perhaps the most interesting note is that they call for a potential change in the current brace position:

...and the current positions recommended in AC 121-24B may need some adjustment to provide an equivalent level of safety for all passenger seat back types.

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  • $\begingroup$ Sorry but I didn't find this copy and paste answer useful personally. What is the conclusion? How does this prove that the position wasn't designed to kill, this is just one source after all. Thanks for your help so far. $\endgroup$ – Cloud Dec 20 '17 at 7:43
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    $\begingroup$ @Cloud the source is a handful of people that used what appears to be the scientific method and crash test dummies to actually test survivability. Your insinuation is that these human beings - many of which will have family or themselves on an airliner at some point- thought it was better to secretly find ways to kill passengers in a survivable crash than it was to help them survive. It would be silly if the plan hit hard but intact and everyone was dead. AND THEN none of them would ever tell anyone - including said family - about their secret agenda. $\endgroup$ – Bageletas Dec 20 '17 at 18:52
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    $\begingroup$ @Cloud "This is just one source" The source is the FAA who did actual crash testing. How can you dismiss this source like it is a random youtube video? $\endgroup$ – OSUZorba Dec 23 '17 at 3:47

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