minimum descent altitude

Also found in: Acronyms.

minimum descent altitude (MDA)

A specified altitude or height in a non-precision approach or circling approach below which descent must not be made without the required visual reference (ICAO). The MDA is referenced to the mean sea level, and the MDH is referenced to the aerodrome elevation or the threshold elevation if that is more than 7 ft (2 m) below the aerodrome elevation. An MDH for a circling approach is referenced to the aerodrome elevation. The required visual reference means that section of the visual aids or of the approach area that should have been in view for sufficient time for the pilot to assess the aircraft position in relation to the desired flight path. In the case of the circling approach, the required visual reference is the runway environment.
Full browser ?