Flight Level - Quadrantal Rule

Quadrantal Rule

This rule applies to IFR flights in the UK both in and outside of controlled airspace except that such aircraft may be flown at a level other than required by this rule if flying in conformity with instructions given by an air traffic control unit, or if complying with notified en-route holding patterns or holding procedures notified in relation to an aerodrome. The rule affects only those aircraft operating under IFR when in level flight above 3,000 ft above mean sea level, or above the appropriate transition altitude, whichever is the higher, and when below FL195 (19,500 ft above the 1013.2 hPa datum in the UK, or with the altimeter set according to the system published by the competent authority in relation to the area over which the aircraft is flying if such aircraft is not flying over the UK.)

The rule is non-binding upon flights operating under VFR.

Minimum vertical separation between two flights abiding by the UK Quadrantal Rule is 500 ft (note these are in geopotential foot units). The level to be flown is determined by the magnetic track of the aircraft, as follows:

• Magnetic Track 000 to, and including, 089° – odd thousands of feet (FL70, 90, 110 etc.)
• Magnetic Track 090 to, and including, 179° – odd thousands plus 500 ft (FL75, 95, 115 etc.)
• Magnetic Track 180 to, and including, 269° – even thousands of feet (FL80, 100, 120 etc.)
• Magnetic Track 270 to, and including, 359° – even thousands plus 500 ft (FL85, 105, 125 etc.)