AIM
4/3/14
7−2−4
Altimeter Setting Procedures
TBL 7
−2−3
ICAO Cold Temperature Error Table
Reported T
emp
_C
Height Above Airport in Feet
200
300
400
500
600
700
800
900
1000
1500
2000
3000
4000
5000
+10
10
10
10
10
20
20
20
20
20
30
40
60
80
90
0
20
20
30
30
40
40
50
50
60
90
120
170
230
280
−10
20
30
40
50
60
70
80
90
100
150
200
290
390
490
−20
30
50
60
70
90
100
120
130
140
210
280
420
570
710
−30
40
60
80
100
120
140
150
170
190
280
380
570
760
950
−40
50
80
100
120
150
170
190
220
240
360
480
720
970
1210
−50
60
90
120
150
180
210
240
270
300
450
590
890
1190 1500
EXAMPLE
−
Temperature
−10 degrees Celsius, and the aircraft altitude is 1,000 feet above the airport elevation. The chart shows that
the reported current altimeter setting may place the aircraft as much as 100 feet below the altitude indicated by the altimeter.
7
−
2
−
4. High Barometric Pressure
a.
Cold, dry air masses may produce barometric
pressures in excess of 31.00 inches of Mercury, and
many altimeters do not have an accurate means of
being adjusted for settings of these levels. When the
altimeter cannot be set to the higher pressure setting,
the aircraft actual altitude will be higher than the
altimeter indicates.
REFERENCE
−
AIM, Paragraph 7
−2−3, Altimeter Errors.
b.
When the barometric pressure exceeds
31.00 inches, air traffic controllers will issue the
actual altimeter setting, and:
1. En Route/Arrivals.
Advise pilots to remain
set on 31.00 inches until reaching the final approach
segment.
2. Departures.
Advise pilots to set 31.00 inch-
es prior to reaching any mandatory/crossing altitude
or 1,500 feet, whichever is lower.
c.
The altimeter error caused by the high pressure
will be in the opposite direction to the error caused by
the cold temperature.
7
−
2
−
5. Low Barometric Pressure
When abnormally low barometric pressure condi-
tions occur (below 28.00), flight operations by
aircraft unable to set the actual altimeter setting are
not recommended.
NOTE
−
The true altitude of the aircraft is lower than the indicated
altitude if the pilot is unable to set the actual altimeter
setting.