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I've heard that the way the plane measures its altitude is to use a barometer to measure air pressure.

Does the pressure at the static ports drop as the aircraft's speed increases?

There is no perfect way to get true static pressure, an answer in the above question has showed that the pressure measured is different along the fuselage. So static pressure error correction(SSEC) must be done to measure true altitude. I think its in a form of lookup table of (angle of attack, angle of slip, gyro angular velocity)=>(SSEC value).

But this lookup table is too hard to build, so I guess, for cost considerations, altimeters are only designed to work in normal flight. When the plane enters spin, the altimeter reading will jump rapidly randomly. Fighter pilots will also see altimeter jumping when they are in dog fights. Is that right?

lotsof one
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    Some aircraft have multiple static ports. For example the Grob-103 has at least 2 and possibly 3 or 4. This reduces the error you mentioned in various situations, including during sideslip. – quiet flyer Mar 22 '23 at 02:52
  • However, it is difficult to prove that the errors can be perfectly compensated by multiple static ports at any fly angle. I guess accurate height is not that important in extreme angles, for example when you enter a spin, you are not taught to watch the altimeter to address the problem. Dog fighters also don't watch altimeter in a fight, they watch their relative height to enemies. When you approach and land, the altimeter will work again and you can use it to help you land. – lotsof one Mar 23 '23 at 01:20
  • If you're in a spin you're supposed to be focusing on getting out of it, not staring at the altimeter to see what it is doing. – Juan Jimenez Mar 27 '23 at 18:11

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