ILS Categories Explained for Simulator Approaches
When NG ROUTE suggests a runway, you may see an ILS CAT label and a decision height figure alongside METAR cloud and visibility data. Those hints help you choose whether an instrument approach is realistic in current conditions — especially when practicing autoland or low-visibility takeoffs and landings in Microsoft Flight Simulator or X-Plane.
What ILS provides
An Instrument Landing System transmits two guidance beams: localizer for horizontal track alignment with the runway centerline, and glideslope for vertical profile, normally a three-degree descent path. Marker beacons or RNAV equivalents mark distance to the threshold. Most airline sim sessions end with an ILS approach unless you deliberately practice RNAV or visual patterns.
Category definitions (simplified)
| Category | Typical decision height | Visibility need |
|---|---|---|
| CAT I | 200 ft above threshold | Moderate — roughly 550 m / 1800 ft RVR and up (airport-specific) |
| CAT II | 100 ft | Low — higher RVR requirements, specialized crew training |
| CAT IIIa | Below 100 ft or no DH | Very low RVR, autoland required |
| CAT IIIb / IIIc | Lower still / none | Minimal to zero RVR; full autoland and rollout control |
Real airports publish exact minima on approach charts. Categories also depend on ground equipment, aircraft certification, and crew authorization. In the sim, rules are relaxed — but flying to CAT I minima in a CAT I-capable aircraft still teaches proper technique.
How NG ROUTE displays ILS data
Runway suggestions combine METAR visibility and ceiling with heuristic ILS category guesses from runway length and known approach availability. You may see:
- ILS CAT I / II / III labels when equipment is likely present
- DA/DH — decision altitude or height for precision approaches
- MDA — minimum descent altitude for non-precision approaches where no glideslope exists
NG ROUTE explicitly notes these are estimates. Always cross-check payware charts or the sim's built-in approach plates for the exact minima of your add-on aircraft.
Matching METAR to category
If METAR reports a 400-foot ceiling and 1200 metres visibility, a CAT I ILS is plausible. If ceiling drops to 100 feet, you are in CAT II territory — assuming the runway supports it and your aircraft is certified in the sim. Below CAT I minima without autoland capability, you should divert to an alternate — NG ROUTE fuel planning already includes diversion reserves for that training mindset.
Flight category badges (VFR, MVFR, IFR, LIFR) give a quick ceiling/visibility summary. LIFR with a CAT I approach available is a classic practice scenario: shoot the approach, decide at DA whether you have the runway environment in sight.
Flying CAT I in the sim
- Set destination QNH from NG ROUTE METAR before descent.
- Arm approach mode on the MCP/FCU when intercepting the localizer.
- At decision height, transition to landing geometry if runways lights are visible; otherwise go around.
Default airliners and payware Airbus/Boeing models handle this differently. FBW, ToLiss, PMDG, and Fenix each have specific autoland arming steps — consult your aircraft manual for CAT III autoland in low visibility.
CAT II and CAT III practice
Use weather presets or live weather when METAR supports it. Reduce runway lights dependency by practicing at night. CAT III autoland requires centerline guidance after touchdown in the real world; few sim setups model rollout to CAT IIIb fidelity, but the approach segment still trains callouts and mode awareness.
When no ILS is available
NG ROUTE marks runways without ILS as NO ILS. You will fly VOR, NDB, RNAV, or visual approaches instead. MDA applies rather than DA — level off at minimums until you see the runway or miss the approach.
Common training mistakes
- Using standard QNH 1013 on approach instead of destination METAR pressure
- Descending below glideslope because the sim exaggerates visibility
- Ignoring crosswind limits for low-visibility autoland (varies by aircraft manual)
- Assuming NG ROUTE DH values replace official chart minima
ILS categories bridge weather briefing and cockpit procedure. Use NG ROUTE METAR plus ILS hints to decide whether today's session is a sunny visual landing or a serious instrument approach — then fly the approach your conditions actually support.
ILS category and decision height values on NG ROUTE are heuristic aids for simulation. Verify all approach minima with official charts for real-world flying.