IFR Fundamentals
The basics of instrument navigation — essential concepts to get started.
Instrument flight (IFR — Instrument Flight Rules) is a set of rules that allow navigation without external visual reference, relying solely on cockpit instruments and radio navigation aids.
Why IFR flight?
In degraded weather conditions (clouds, fog, night), the pilot cannot rely on visual references. IFR flight allows you to:
- Navigate safely without outside visibility
- Follow precise routes defined by ground-based aids
- Perform approaches to aerodromes in IMC (Instrument Meteorological Conditions)
Key concepts
The speed triangle
In IFR flight, three speeds are fundamental:
| Speed | Symbol | Description |
|---|---|---|
| Indicated airspeed | IAS | Read on the airspeed indicator, used for flying |
| True airspeed | TAS | Speed of the aircraft relative to the air (corrected for altitude/temperature) |
| Groundspeed | GS | Speed relative to the ground, resulting from TAS + wind |
Heading and track
- Heading : Direction the nose of the aircraft is pointing
- Track : Actual path over the ground
- Drift : Angle between heading and track, caused by wind
Directional references
- Magnetic north : Reference for the compass (magnetic declination relative to true north)
- QDM : Magnetic heading to reach a station
- QDR : Magnetic bearing from a station
- Radial : QDR expressed from a VOR (magnetic)