"Icebound" wrote in message
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"Gig Giacona" wrote in message
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"jharper aaatttt cisco dddooottt com" "jharper aaatttt cisco dddooottt
com" wrote in message news:1105391055.635118@sj-nntpcache-3...

Anyone know?



The following is a WAG but that could be the reason that in the Flight
Levels, above 18k feet everyone sets thier altimeter to 29.90.



Hopefully, 29.92.



That still wouldn't help since the pressure change for a 1000ft change in
altitude at 18k would be smaller than at sea level. It would have to have
some non-linear spring compensation as a function of absolute pressure.