Definition
Adjustments applied to indicated altitude to account for the fact that pressure altimeters are calibrated for a standard atmosphere (15 °C at sea level), and when actual air temperature is colder than standard, the altimeter overreads — the aircraft is actually lower than indicated. In cold weather, pilots add a correction (from an ICAO cold temperature correction table) to published altitudes on instrument approach and departure procedures to maintain required obstacle clearance.
Plain English
Cold air is denser and sits lower, so on a cold day your altimeter shows you higher than you really are. To stay safely above terrain and obstacles, you add a few extra feet to the altitudes on your approach chart based on how cold it is.
Context Anchor
Seen in instrument flying when using minimum altitudes during cold weather, especially on approaches, departures, and routes near terrain or obstacles.
Derivation
Correction comes from a Latin idea meaning “to make right.” In this use, the pilot is making the altitude value right for the actual air temperature instead of trusting the uncorrected altimeter reading.
Why Pilots Care
Prevents descent below safe terrain clearance during cold-weather instrument flight.
Grounding Statement
Cold air changes the spacing of pressure levels, so the altimeter can look normal while the airplane is actually lower than expected.
Intuition Check
Do not assume setting the current altimeter setting removes this error. The altimeter setting corrects for local pressure; temperature corrections account for cold air making indicated altitude higher than true altitude.
Example Sentence 1
With the surface temperature at -30 °C, the captain applied a temperature correction of 200 feet to the minimum descent altitude before starting the approach.
Example Sentence 2
The crew consulted the temperature correction table and climbed to the adjusted MEA for the segment.