Similarly, as height above the reporting station increases, the effects of a non-standard-temperature lapse rate will cause a larger error in the indicated altitude. Therefore, in order to correct for the effect of cold temperature on an altimeter, both the actual temperature and the aircraft's height above the reporting station need to be considered.
This is added to 2800 feet, giving you a new minimum indicated altitude of 3120 feet at JIPAS--you may want to round that up to 3200--which you report to ATC.
The potential problem arises because stepdown fix altitudes are published using indicated altitudes
that vary with temperature, but altitudes along a glideslope are unaffected by temperature.
is the value displayed on the pressure altimeter.
Hysteresis error is a lag in indicated altitude
due to the elastic properties of the material within the altimeter.
Do a similar exercise for an MDA about 1000 feet above the airport at -40 degrees C and you'll see why an airliner got a GPWS alert at Kelowna, B.C., on approach even though they were dead-on for the indicated altitude
. Some airlines have a correction chart to use when the temp goes below zero degrees C--and some don't.
If a three-degree standard glideslope is elected, dividing by 300 the indicated altitude
minus the field elevation will determine a start-down point from the runway.
Add this to the elevation of the airport (or touchdown zone, if you'd like to be precise), and it should be close to your indicated altitude
as you slide down the glideslope.
The fact that the area he is flying in is not designated as mountainous does not change the fact that it is mountainous, and altimeter errors due to venturi effects, etc., can make the indicated altitude
higher than true altitude.