6/17/21
AIM
Section 3. Cold Temperature Barometric Altimeter
Errors, Setting Procedures and Cold Temperature
Airports (CTA)
7
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3
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1. Effect of Cold Temperature on
Barometric Altimeters
a.
Temperature has an effect on the accuracy of
barometric altimeters, indicated altitude, and true
altitude. The standard temperature at sea level is 15
degrees Celsius (59 degrees Fahrenheit). The
temperature gradient from sea level is minus 2
degrees Celsius (3.6 degrees Fahrenheit) per 1,000
feet. For example, at 5000 feet above sea level, the
ambient temperature on a standard day would be 5
degrees Celsius. When the ambient (at altitude)
temperature is colder than standard, the aircraft’s true
altitude is lower than the indicated barometric
altitude. When the ambient temperature is warmer
than the standard day, the aircraft’s true altitude is
higher than the indicated barometric altitude.
b.
TBL 7
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3
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1 indicates how much error may exist
when operating in non
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standard cold temperatures.
To use the table, find the reported temperature in the
left column, and read across the top row to locate the
height above the airport (subtract the airport elevation
from the flight altitude). Find the intersection of the
temperature row and height above airport column.
This number represents how far the aircraft may be
below the indicated altitude due to possible cold
temperature induced error.
TBL 7
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3
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1
ICAO Cold Temperature Error Table
7
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3
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2. Pre
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Flight Planning for Cold
Temperature Altimeter Errors
Flight planning into a CTA may be accomplished
prior to flight. Use the predicted coldest temperature
for plus or minus 1 hour of the estimated time of
arrival and compare against the CTA published
temperature. If the predicted temperature is at or
below CTA temperature, calculate an altitude
correction using TBL 7
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3
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1. This correction may be
used at the CTA if the actual arrival temperature is the
same as the temperature used to calculate the altitude
correction during preflight planning.
7
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3
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3. Effects of Cold Temperature on
Baro
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Vertical Navigation (VNAV) Vertical
Guidance
Non
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standard temperatures can result in a change to
effective vertical paths and actual descent rates when
using aircraft baro
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VNAV equipment for vertical
guidance on final approach segments. A lower than
standard temperature will result in a shallower
descent angle and reduced descent rate. Conversely,
a higher than standard temperature will result in a
steeper angle and increased descent rate. Pilots
should consider potential consequences of these
effects on approach minima, power settings, sight
Cold Temperature Barometric Altimeter Errors, Setting Procedures and Cold Temperature
7
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3
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1
Airports (CTA)