I'm an aviation enthusiast (I do not, nor have I ever worked in the industry), and after researching several various emergencies (reading text documents, reviewing CVR transcripts and watching documentaries and TV shows such as Air Crash Disaster/Mayday), I'm curious as to why so many spatial disorientation situations have resulted in the loss of aircraft.

My thinking is that even if there is zero visibility combined with possible instrument failure causing disorientation, why don't aircraft have a simple glass ball half-filled with water set atop the console?

Wouldn't that provide a crude but reasonably accurate aircraft attitude? I mean:

  • water is at the top of the ball (ie. toward the ceiling), plane is inverted
  • water is angled toward the left of the ball, plane is banking left (similarly for right)
  • water is angled forward, plane is nose down
  • water is angled aft, plane is nose up

Even if a/both pilot(s) were fully disoriented due to whatever situation to the point they believe their attitude and other instruments aren't jiving with what their balance is telling them, a quick look at such a simple device would at least indicate a reasonable measure of sanity, wouldn't it?

Now, water might be too viscous a fluid for this, but replace with an oil or similar to minimize movement due to vibration etc.

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    $\begingroup$ wonders.physics.wisc.edu/water-pail In flight, acceleration feels the same as gravity, and can appear in any direction, including completely sideways or upside-down from true gravity. A globe of water is subject to acceleration. If the plane does an abrupt loop, the water will maintain its position in the globe, even as the globe turns upside down! (like swinging a bucket over your head). The only known way to measure attitude is a gyroscope (and related variants, MEMS, laser-ring) $\endgroup$
    – abelenky
    Aug 20 '19 at 16:39
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    $\begingroup$ @abelenky Indeed, and it's totally counter-intuitive. That's why it is so dangerous to trust your guts when there's no actual vision and also the reason why flight simulators work and can give the impression of basically all attitudes even though they are fixed to the ground. $\endgroup$
    – PerlDuck
    Aug 20 '19 at 17:09
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    $\begingroup$ This video demonstrates clearly why your idea would not work: youtube.com/watch?v=V9pvG_ZSnCc $\endgroup$ Aug 20 '19 at 17:21
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    $\begingroup$ FAA studies have shown that non-IFR rated pilots last about 2 minutes before losing control when instrument conditions develop (or when they fly into clouds, or into very low visibility conditions). 2 minutes, that is not long. Part of our training is to keep the plane at same altitude and perform a 180 degree turn to get out of the IMC condition. Only takes 1 minute to perform a 180 degree turn at standard rate of turn. If the plane is not equipped with a turn coordinator or attitude indicator/artificial horizon, the standard bank angle can be difficult to determine, ->> loss of control. $\endgroup$
    – CrossRoads
    Aug 20 '19 at 17:43
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    $\begingroup$ "My thinking is that even if there is zero visibility combined with possible instrument failure causing disorientation," IFR equipped planes also have several means to determine if they are making uncommanded turns: the artificial horizon/attiude indicator (vacuum gyro, or solid state these days), the turn coordinator gyro (usually an electric gyro), the whiskey compass or vertical card compass, the directional gyro/Horizontal Situaiton Indicator (HSI) (vacuum gyro, or solid state these days). There's 4, moving map GPS would be another indicator. Proper train and practice help too. $\endgroup$
    – CrossRoads
    Aug 20 '19 at 17:53