AIM ¶ 7-3-2 — Cold Temperature Altimeter Pre-Flight Planning
AIM 7-3-2 explains pre-flight planning for Cold Temperature Airport altimeter errors, including how to compute altitude corrections using TBL 7-3-1.
When you're flying into a Cold Temperature Airport (CTA), the AIM recommends planning for altimeter errors before you takeoff — not just reacting in the cockpit. In very cold air, your altimeter reads higher than your true altitude, which can erode terrain and obstacle clearance on instrument approaches.
Here's the pre-flight workflow described in AIM 7-3-2:
- Look up the predicted coldest temperature for a window of plus or minus 1 hour around your ETA.
- Compare that forecast temperature against the CTA published (cold temperature restriction) temperature for the airport.
- If the predicted temperature is at or below the published CTA temperature, calculate an altitude correction using TBL 7-3-1.
- You may use that pre-computed correction at the CTA only if the actual arrival temperature matches the temperature you used during planning.
Why it matters: pre-planning the correction reduces cockpit workload during a high-stress IFR arrival and ensures you're applying the right number to the right segment of the approach. Remember, the AIM is informational guidance — but the underlying ICAO/CTA correction procedure is operationally important for terrain clearance.