
14/08/2025
⭕️ILS Categories – Landing in Low Visibility Made Simple
The Instrument Landing System (ILS) helps pilots land safely when visibility is poor. It uses radio signals to guide the aircraft’s approach and landing. ILS is divided into categories based on how low you can go before you must see the runway.
Category I (CAT I)
* Decision Height (DH): 200 ft above runway
* Runway Visual Range (RVR): ≥ 550 m (1,800 ft)
* Use: Standard precision approach in moderate fog or low cloud.
Category II (CAT II)
* DH: 100 ft
* RVR: ≥ 300 m (1,200 ft)
* Use: For thicker fog or very low cloud ceilings.
Category III
* CAT IIIa: DH < 100 ft, RVR ≥ 200 m
* CAT IIIb: DH < 50 ft (sometimes 0 ft), RVR ≥ 75 m
* CAT IIIc: No DH, No RVR limit – full auto-land in zero visibility (rarely used operationally).
In Simple Terms:
* CAT I – You need to see the runway fairly early.
* CAT II – You can land with very little visual reference.
* CAT III – The aircraft can land almost entirely on instruments, even if you see *nothing* until you’re on the ground.