Background
Instrument approach
Updated: 2010-09-02 16:52
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In aviation, an instrument approach or instrument approach procedure (IAP) is a type of air navigation that allows pilots to land an aircraft in reduced visibility (known as instrument meteorological conditions or IMC), or to reach visual conditions permitting a visual landing.
The publications depicting instrument approach procedures are called Terminal Procedures, but are commonly referred to by pilots as "approach plates". These documents graphically depict the specific procedure to be followed by a pilot for a particular type of approach to a given runway. They depict prescribed altitudes and headings to be flown, as well as obstacles, terrain, and potentially conflicting airspace. In addition, they also list missed approach procedures and commonly-used radio frequencies.
Approaches are classified as either precision or nonprecision, depending on the accuracy and capabilities of the navigational aids (navaids) used. Precision approaches utilize both lateral (localizer) and vertical (glideslope) information. Nonprecision approaches provide lateral course information only.
