Definition
The lowest altitude, expressed in feet above mean sea level, to which a pilot may descend during a circling instrument approach until the aircraft is in a position to make a normal descent for landing. The aircraft must remain at or above this altitude while maneuvering visually around the airport, until established on a path from which a normal landing can be made.
Plain English
When you fly an instrument approach but need to circle the airport before landing, this is the lowest height you're allowed to go down to while you're still circling. You stay at this height until you're lined up to land normally.
Context Anchor
Seen on instrument approach charts and in cold-temperature correction tables when deciding how low the aircraft may descend during a circling approach.
Derivation
"Circling" describes maneuvering the aircraft visually around the airport. "Minimum Descent Altitude" comes from "minimum" (Latin minimus, smallest) and "descent" — together meaning the lowest altitude permitted during the descent portion of this type of approach.
Why Pilots Care
Ensures required obstacle clearance while maneuvering to align with the landing runway after passing the final approach fix.
Grounding Statement
Think of this altitude as a protected floor: stay at or above it until you can see enough and are positioned well enough to make a normal landing.
Intuition Check
“Circling” does not mean simply flying in a circle. Here it means visually maneuvering near the airport after an instrument approach to reach the runway for landing. “Minimum” does not mean a target altitude to reach as soon as possible; it is the lowest altitude allowed until landing descent is safe.
Example Sentence 1
After breaking out of the clouds, the pilot leveled at the circling minimum descent altitude and maneuvered to align with the landing runway.
Example Sentence 2
Apply the cold temperature correction from the ICAO table to the circling minimum descent altitude before beginning the approach.