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why high to low, look out below?
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November 11th 05, 03:42 AM
Rich Lemert
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why high to low, look out below?
wrote:
i'm studying for my private license and i am a bit confused about this
high to low, look out below. the way I see it:
imagine an altimeter sitting at sea level. lets say the atomspheric
pressure at the location of the altimeter is "10" (no units, just for
simplicity). now lets say you set the altimeter to "10". so now the
altimeter reads "0 feet"
now decrease the temperature of the air surrounding the altimeter, and
since the colder air gets the more dense it gets, the atmospheric
pressure goes up. the altimeter doesnt know this. all it sees is an
increase in pressure, which it thinks means an decrease in altitude, so
it indicates say "-10 feet". this is directly contrary to the "high to
low look out below" because the altimeter is telling you you are 10
feet lower than you are, which is not what that saying is implying.
SO WHATS THE DEAL?
If I'm not mistaken, the phrase "high to low" means you are moving
from a region of higher barometric pressure to one with a lower
barometric pressure. Your altitude does not change, but because
your altimeter is seeing a lower pressure it thinks your altitude
is higher than it really is. You "think" you're at 100 ft, but you've
actually just landed.
The situation you described is more accurately referred to as "low
to high".
Rich Lemert