- Ground-based navaids
- Precision and non-precision approaches
- ILS categories
- RNAV (GNSS) approaches
- The missed approach
Instrument approaches get you from the arrival to a point where you can see the runway and land. Each type relies on a different kind of guidance.
Ground-based navaids
| Navaid | Frequency band | What it gives you |
|---|---|---|
| VOR | 108.00 to 117.95 MHz | A bearing (radial) from the station |
| DME | Paired with a VOR or ILS | Slant distance to the station |
| NDB | 190 to 1,750 kHz | A direction to the station, shown on an ADF needle |
| ILS localizer | 108.10 to 111.95 MHz | Left-right guidance to the runway centreline |
| ILS glide slope | Paired with the localizer | Up-down guidance, usually on a 3° path |
The airport page lists the navaids within 40 NM, with their frequencies.
Precision and non-precision approaches
A precision approach gives lateral and vertical guidance to a decision altitude (DA). At the DA you either see the runway environment and continue, or you go around. The ILS is the classic example.
A non-precision approach gives lateral guidance only. You descend to a minimum descent altitude (MDA) and may stay level there until the missed approach point. VOR, NDB and LNAV approaches are non-precision.
ILS categories
| Category | Typical minima |
|---|---|
| CAT I | Decision height 200 ft, visibility 800 m or RVR 550 m |
| CAT II | Decision height 100 ft, RVR 300 m |
| CAT III | Lower still, down to no decision height for some operations |
CAT II and III need special equipment, certification and crew training. In the simulator, check that your aircraft model supports autoland before you try one.
RNAV (GNSS) approaches
Satellite approaches appear on charts as RNAV (GNSS) or RNP, with several lines of minima:
- LNAV: lateral guidance only, flown to an MDA.
- LNAV/VNAV: lateral and barometric vertical guidance, flown to a DA.
- LPV: precision-like guidance from satellite-based augmentation, flown to a DA often as low as an ILS CAT I.
- RNP AR: tightly designed approaches that need specific approval.
Fly the line of minima your aircraft and its database support.
The missed approach
Every approach ends with a published missed approach. Brief it before you start the approach, not after you reach the minimum: the first turn and the first altitude are the parts you will need without time to read.
For flight simulation and training only. Real-world procedures vary by country and operator; always follow the published charts and your local rules.
Keep reading
- Holding patterns: How a hold is flown, the three entries, leg timing and speed limits.
- Planning the descent: Work out where to start down and how fast to descend, with the 3-to-1 rule and a check you can do in your head.