AIM Text
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 7-3-1. 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.
Source: FAA Aeronautical Information Manual · current edition · paragraph 7-3-2.
The short answer
This AIM section is FAA advisory guidance on pre-flight planning for Cold Temperature Altitude (CTA) errors. It tells pilots to use the predicted coldest temperature within plus or minus 1 hour of estimated arrival, compare it to the published CTA temperature, and if at or below it, calculate an altitude correction from TBL 7-3-1.
Research Notes
Common Questions
What temperature should I use when planning for a cold temperature airport?
The AIM advises using the predicted coldest temperature for plus or minus 1 hour of your estimated time of arrival, then comparing it against the CTA published temperature.
When do I need to calculate an altitude correction for a cold temperature airport?
Per the AIM, if the predicted temperature is at or below the CTA temperature, you calculate an altitude correction using TBL 7-3-1. This correction may be used at the CTA if the actual arrival temperature matches the temperature used during preflight planning.
Can I do cold temperature altitude planning before the flight?
Yes. The AIM states flight planning into a CTA may be accomplished prior to flight, and a precomputed correction may be applied at the CTA when the actual arrival temperature is the same as the one used in preflight planning.