Aviation glossary

What is IMC?

Instrument Meteorological Conditions

IMC (Instrument Meteorological Conditions) is weather below the visual minima, where flight must be by reference to instruments.

IMC is any weather worse than the minima that define VMC: typically low cloud, poor visibility, or both. In IMC a pilot cannot navigate by outside reference and must fly on instruments under IFR.

In the UK, a PPL holder needs an IR(R) (formerly the IMC rating) or a full Instrument Rating to fly legally in IMC.

Related terms

VMCVMC (Visual Meteorological Conditions) is weather good enough to fly visually, meeting the minimum visibility and distance-from-cloud requirements for VFR.IFRIFR (Instrument Flight Rules) is flying by reference to the aircraft's instruments, used in poor weather or by choice, under a defined set of rules.IR(R)The IR(R), formerly the IMC rating, is a UK rating that lets a PPL holder fly in instrument conditions within UK airspace, with defined privileges and limitations.

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