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.
References in periodicals archive ?
Another theme running through these accidents is descending below the circling minimum descent altitude (MDA).
This concept, which received a lot of visibility in the 1990s, is the stabilized-approach alternative to the time-honored practice of crossing the FAF or an intermediate, step-down fix on a non-precision approach (NPA) and then increasing the aircraft's rate of descent to arrive at the minimum descent altitude (MDA) well in advance of reaching the airport.
Another way to keep it all straight is to look for the decision altitude (DA) designation versus the minimum descent altitude (MDA) abbreviation on the approach plate's minima line.
She noticed the airplane was "high and fast" on final approach, so she used speed brakes and flaps to slow the airplane and descend to the minimum descent altitude.
Procedures using GPS to generate an electronic glidepath through baro-VNAV may not provide obstacle clearance below the procedure's minimum descent altitude (MDA).
The NTSB's probable cause finding included "the flight crew's operation of the airplane below the minimum descent altitude without an appropriate visual reference for the runway" and the FAA's "unclear wording" of a Notam on nighttime restrictions for the VOR/DME-C procedure the crew was executing, along with "the FAA's failure to communicate" the Notam's restriction to the tower.
The Cessna crew, however, made a mistake common when flying non-precision approaches with a minimum descent altitude (MDA) level-off.
Imagine flying at minimum descent altitude (MDA) on a murky day with rain streaming up the windscreen, peering out the front of the airplane, looking for a gray runway on an even grayer afternoon.

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