"Terence Wilson" wrote in message
...
On Sun, 21 Oct 2007 20:06:30 -0400, "An Aviator"
wrote:

Current temperature is not used to convert
pressure to altimeter settings.

Can you please elucidate? Isn't current temperature implicitly used if
we use a barometer to measure local pressure and then extrapolate the
pressure at sea level (to be used in the Kollsman window)?

The altimeter is calibrated using the ISA and the temperature under ISA is
15C.

Setting the altimeter to read airfield elevation in no way is a real
representation of what the sealevel pressure is precisely because no
adjustment is made for temperature.

Have a look at the cold weather adjustments needed for instruments
approaches. As the temperature deviates from ISA whilst the altimeter could
be reading 200' you will actually be well under and enough to bust a
checkride. For example, an ISA deviation of -15C is an correction of 12'.
approximately 4ft/1000ft for each C of difference. In this case, -15C ISA
is only a temperature of 0C or 32F.