"Canucker Trucker" <flamindakman@yahoo.co.uk> wrote:
: one major problem with using barometric air pressure readings is that they
: are 'corrected' for altitude ... i.e.my barometer here reads 1.0 atm, but
: its really .95 atm absolute pressure (1.0 atm would be at sea level) ...
: it's really messed up but the reason they do that is so weather guys don't
: get confused. Best thing would be if the track you were at has an absolute
: pressure gauge. That's the key .. it has to be absolute without any
: altitude correction.
Canuck,
I'm not sure what you mean. Are you referring to getting the readings
from a TV or radio weather report? I just read the number off my
el-cheapo barometer, which has no idea what altitude it is at. This is
why aircraft altimeters have an adjustment dial. When you put the plane
away after flying it and come back the next day, chances are extremely
high that the needle isn't reading the correct altitude; I have seen
differences of hundreds of feet when the plane has done nothing but sit
in the hangar. One of the first things a pilot will do during the
preflight or cockpit checklist is to reset his altimeter to field
elevation, because even an expensive aircraft altimeter really has no
idea what its true elevation is - its only a barometer which needs to
be corrected to some known quantity before it is accurate. In fact,
on a cross country flight, pilots will get pressure readings from
ground stations which they dial into their altimeters to keep them
accurate as they fly through different weather systems.
---Jon-
.---- Jon Steiger ------ jon@dakota-truck.net or jon@jonsteiger.com -----. | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL | | '70 Barracuda, '92 Ram 4x4, '96 Dakota, '96 Intruder 1400, '96 FireFly | `----------------------------------------- http://www.jonsteiger.com ----'
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