Ask A Scientist© General Science Archive

name         vandewattyne
status       educator
age          50s

Question -   Why do many people sitting in a plane have troubles with
their ears when the plane takes off?  I thought the plane was completely
isolated from the outside?  How can there be a different in pression?

The pressure in the cabin is regulated by the flight crew.  They need to be
able to change it to match the varying pressure of the different places they
want to open the door.  If they didn't it might be quite a POP when they brake
the seal.  It may also vary slightly as the aircraft change power setting
(because the engines run the compressors).

Larry Krengel
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The cabin is pressurized after the doors are shut.  When  you go up in
altitude, the atmospheric pressure goes down so in order to be able to
breathe at that altitude the cabin has to pressurized.  In your head,  you
have 2 eustacian tubes that connect your mouth with your inner ear.  They are
there to be able to equalize the pressure on both sides of your eardrum.  As
the plane climbs in altitude the pressure on the inside of your head doesn't
change as fast as the pressure outside the ear and pressure build up in your
head.  If you open your mouth or chew gum sometimes you can cause the air in
your inner ear to be forced out through your eustacian tubes and you hear a
pop.
Van Hoeck
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