4/20/23
AIM
Section 3. Cold Temperature Barometric Altimeter
Errors, Setting Procedures and Cold Temperature
Airports (CTA)
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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.
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
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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
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.
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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
Cold Temperature Barometric Altimeter Errors, Setting Procedures and Cold Temperature
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3
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1
Airports (CTA)