Learn what makes a runway a precision approach runway, which guidance and lighting are required, how CAT I–III differ, and why PAPI does not count.
A precision approach runway is a runway end served by an approved instrument approach providing continuous lateral and vertical guidance to defined minima, with the required visual aids, obstacle protection, monitoring and operating procedures. The classification applies to that runway direction, and its category depends on the authorised decision height and visibility or RVR.
In Aviation & Real-World Flying terms, precision describes the approved guidance and operating standard—not how accurately the pilot lands, how long the runway is or how elaborate its lights appear.
What equipment makes an approach runway precision?
No single light or antenna creates the designation; it is the approved combination of instrument guidance, runway facilities and operating standards.
- Lateral and vertical guidance: The system must guide the aircraft in both azimuth and elevation. ILS is the familiar example, while approved GLS, MLS and precision approach radar can also support precision approaches.
- A protected approach: Obstacle clearance, surveyed flight paths and protected navigation-signal areas must meet the applicable standard. ILS critical and sensitive areas may need protection from aircraft and vehicles during low-visibility operations.
- Suitable visual aids: Required markings and lights vary with the category. They can include approach lights, runway edge and centreline lights, touchdown-zone lights and threshold identification. Our explanation of how approach-light patterns support the transition to visual flight covers their separate role.
- Monitoring and reliability: Navigation transmitters, lighting, standby power and runway visual range equipment must have the monitoring and redundancy required for the authorised category.
- A published and approved procedure: The approach must have protected segments, defined missed-approach instructions and published minima. Suitable hardware without an approved procedure does not establish an operational precision approach.
Do ILS, PAPI and approach lights all count?
ILS is the commonest precision system, but neither PAPI nor approach lighting substitutes for approved lateral-and-vertical instrument guidance.
| System or aid | Guidance provided | Does it establish precision status? |
|---|---|---|
| ILS | Localiser lateral guidance and glide-path vertical guidance | Yes, when the procedure and runway facilities are approved |
| GLS, MLS or precision approach radar | Approved lateral and vertical guidance | Yes, where supported and authorised |
| RNAV LPV or LNAV/VNAV | Lateral and vertical guidance | Usually classified as an approach with vertical guidance rather than a traditional precision approach; terminology can vary by authority |
| PAPI or VASI | Visual vertical-path indication only | No; see how PAPI colour indications show whether an aircraft is high or low |
| Approach and runway lights | Visual alignment, distance and runway references | No; they support the operation but do not provide electronic glide-path guidance |
A mistake we see often is calling any runway with PAPI lights a precision runway. PAPI helps after the runway environment is visible; it neither creates an instrument procedure nor supplies course guidance.
What do CAT I, CAT II and CAT III mean?
CAT I, II and III permit progressively lower operating minima and demand progressively greater capability from the airport, aircraft, crew and operator.
| Category | Typical ICAO basis |
|---|---|
| CAT I | Decision height not below 200 ft, with visibility of at least 800 m or RVR of at least 550 m |
| CAT II | Decision height below 200 ft but not below 100 ft, with RVR generally at least 300 m |
| CAT IIIA | Decision height below 100 ft or none, with RVR generally at least 175 m |
| CAT IIIB | Decision height below 50 ft or none, with RVR below 175 m but generally not below 50 m |
| CAT IIIC | No decision height and no RVR limitation in the formal definition; it is not a routinely available operational capability |
National rules and individual approvals can use different RVR values, so the applicable chart and operating regulations take precedence over this summary. A CAT III runway also does not make every aircraft CAT III capable. The aircraft systems, crew qualifications, operator approval, weather and equipment status must all permit the operation.
CAT III often involves autoland, but autoland is not the definition of a precision approach runway. Some authorities permit other specifically approved landing-guidance systems.
Can only one end of a runway be precision?
Yes. Precision capability is assigned to an individual landing direction, so opposite ends of the same physical runway can have different approach types and categories.
For example, Runway 09 might have a CAT II ILS while Runway 27 has only an RNAV or visual approach. The pavement, markings and some lighting are shared, but the procedure, navigation installation, obstacles and authorised minima are direction-specific.
How do you identify a precision approach runway?
The instrument approach chart, not the runway's appearance, is the reliable source for identifying precision capability.
- Read the procedure title: Look for an approved precision type such as ILS or GLS and any stated category. A chart titled “ILS or LOC” can contain precision ILS minima and separate non-precision localiser-only minima.
- Check the profile and minima: Confirm that the procedure supplies both course and glide-path guidance. Decision altitude or height alone is not proof, because approaches such as LPV also use a DA/H.
- Match the runway direction: Confirm the runway number, inbound course, navigation source and applicable category. The opposite end may not have the same capability.
- Verify operational status: Real-world crews check published notices and airport information. In a simulator, the navigation database, aircraft avionics and scenery may represent different data cycles.
Our guide to finding procedure titles, profiles and minima on an instrument chart explains where these details appear.
Does an equipment failure stop a precision approach?
An outage can make the precision procedure unavailable or raise its minima even though the airport's underlying runway classification remains unchanged.
- If the ILS glide path fails, a published localiser-only procedure may remain available, but it is flown to non-precision minima.
- If the approach lights fail, lateral and vertical electronic guidance may remain usable while the required visibility or RVR increases.
- Failures affecting RVR sensors, centreline lights, touchdown-zone lights, standby power or signal monitoring can suspend CAT II or CAT III operations.
- In a simulator, a procedure can appear in the flight-management system even when the scenery's transmitter is missing, incorrectly positioned or using incompatible navigation data.