CAT III precision approach is an advanced aviation landing procedure allowing aircraft to land in very low or zero visibility, using sophisticated onboard automation and specialized ground systems. It enhances operational reliability at major airports during adverse weather conditions.
A Category III (CAT III) precision approach is the highest level of precision instrument approach procedure in civil aviation. It enables aircraft to land safely during extremely poor visibility—specifically, when the decision height (DH) is less than 100 feet above the runway, or in some cases, when no DH is specified at all. In such conditions, pilots may not see the runway until just before touchdown, or, for no-DH procedures, not until after landing.
CAT III approaches represent the pinnacle of aviation safety technology and operational sophistication, integrating:
These approaches are essential for maintaining airport capacity, minimizing delays, and ensuring safety at major international hubs affected by frequent fog, snow, or rain.
Both the Federal Aviation Administration (FAA) and the International Civil Aviation Organization (ICAO) define CAT III as a precision approach with a DH under 100 feet or none at all and/or RVR below 1,000 feet (300 meters). ICAO further divides Category III into three subcategories:
| Category | Decision Height (DH) | Runway Visual Range (RVR) | Typical Use |
|---|---|---|---|
| CAT IIIA | <100 ft or no DH | ≥700 ft (200 m) | Most commercial jets |
| CAT IIIB | <50 ft or no DH | <700 ft, but ≥150 ft (50 m) | Advanced autoland, fail-op |
| CAT IIIC | No DH | No RVR limitation | Full automation (not in use) |
Note: CAT IIIC is not practically used due to the lack of safe taxiing solutions in zero visibility, despite being defined in standards.
CAT III approaches are used to maintain safe and reliable flight operations when weather causes visibility to drop below the minimums for conventional (CAT I or II) approaches. This is most critical at busy international airports where even brief weather disruptions can lead to widespread delays and diversions.
CAT III is typically employed by:
Airline Operations in Dense Fog
An Airbus A350 inbound to Frankfurt during a fog event is cleared for a CAT IIIA approach. With an RVR of 800 feet, both autopilots and autoland are engaged. Visual contact with the runway is only acquired after touchdown.
Emergency Medical Flight
An air ambulance must land in low visibility at a hospital-served airport. CAT III capability ensures the mission proceeds safely and on schedule, even in thick fog.
Weather-Resilient Hubs
Airports like London Heathrow or Paris CDG routinely use CAT III to sustain high traffic volumes during adverse weather, minimizing schedule disruptions.
To conduct CAT III approaches, an aircraft must have:
Advanced features such as Head-Up Displays (HUDs) or Enhanced Vision Systems (EVS) may be used for added situational awareness but are not mandatory.
The airport must provide:
All equipment must be monitored and maintained to rigorous standards to guarantee availability and reliability.
Only crews who:
are authorized to perform CAT III approaches.
Operators must:
A specified height above the runway at which the pilot must decide to land or go around. For CAT IIIA, DH is <100 ft; for CAT IIIB, <50 ft; for CAT IIIC, there is no DH.
A real-time, instrument-measured value of visibility along the runway. RVR is the primary criterion for determining if a CAT III approach may be initiated or continued.
A highly integrated automation system that guides the aircraft from approach through flare, touchdown, and rollout, without manual pilot input.
A predetermined radio altimeter height (typically 200 ft) below which any system failure requires a go-around.
Example 1: CAT IIIA at London Heathrow
A B777 lands in thick fog using autoland; pilots gain visual contact with the runway only after touchdown.
Example 2: CAT IIIB at Frankfurt
An A320 lands with an RVR of 200 feet; the crew relies entirely on fail-operational automation, acquiring visual cues only after rollout.
Example 3: CAT IIIC (Theoretical)
Regulations define CAT IIIC for zero-visibility landing and rollout, but it is not operationally used due to taxi safety concerns.
CAT III precision approaches are crucial for ensuring safe, reliable, and efficient commercial aviation operations in low-visibility conditions. They rely on advanced automation, certified infrastructure, and rigorous training, enabling airlines and airports to maintain schedules and safety standards even in the most challenging weather.
If your operation or airport is considering CAT III implementation, ensure comprehensive planning for equipment, infrastructure, training, and regulatory approval.
For more on aviation safety and technology, explore our detailed aviation glossary .
A CAT III precision approach is an advanced instrument landing procedure that permits aircraft to land in extremely poor visibility conditions, with decision heights below 100 feet or even no specified decision height. This is made possible by sophisticated onboard systems, airport infrastructure, and specialized crew training.
CAT IIIA allows landing with a decision height below 100 feet or no DH and RVR not less than 700 feet. CAT IIIB permits landing with a decision height below 50 feet or no DH and RVR as low as 150 feet. CAT IIIC, defined in regulations, theoretically allows landing and rollout in zero visibility with no DH or RVR requirement, but it is not currently authorized in operational use due to taxi safety limitations.
Aircraft must have redundant autopilots, dual ILS receivers, autothrottle, radio altimeter, and autoland systems for CAT III approaches. Airports must provide certified ILS, high-intensity lighting, and real-time RVR measurement. Both aircraft and airport infrastructure must be certified for CAT III operations.
Only crews and operators specifically trained and authorized by their national aviation authority can conduct CAT III approaches. They must meet strict regulatory, training, and proficiency requirements, and use certified aircraft and airports.
CAT III operations allow airlines and airports to maintain flight schedules and minimize weather-related delays or diversions during periods of low visibility, such as fog or heavy precipitation. This capability is crucial for major international hubs and airlines operating in challenging climates.
Reduce delays and maintain efficient operations during low-visibility conditions with CAT III-certified systems and crew training.
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