What does IMC mean in Transportation?
This page is about the meanings of the acronym/abbreviation/shorthand IMC in the Governmental field in general and in the Transportation terminology in particular.
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What does IMC mean?
- Instrument meteorological conditions
- Instrument meteorological conditions is an aviation flight category that describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules, rather than by outside visual references under Visual Flight Rules. Typically, this means flying in cloud or bad weather. Pilots sometimes train to fly in these conditions with the aid of products like Foggles, specialized glasses that restrict outside vision, forcing the student to rely on instrument indications only. The weather conditions required for flight under VFR are known as Visual Meteorological Conditions. IMC and VMC are mutually exclusive. In fact, instrument meteorological conditions are defined as less than the minima specified for visual meteorological conditions. The boundary criteria between VMC and IMC are known as the VMC minima, around which are known as "marginal VMC". With good visibility, pilots can determine the attitude of the aircraft by utilising visual cues from outside the aircraft, most significantly the horizon. Without such external visual cues, pilots must use an internal cue of attitude, which is provided by gyroscopically-driven instruments such as the attitude indicator. The availability of a good horizon cue is controlled by meteorological visibility, hence minimum visibility limits feature in the VMC minima. Visibility is also important to avoid terrain.