PAPI Settings
Pilot Position
Report Details
All Indications
| Bar (nearest runway first) | Meaning | Angle band (°) | Height band above PAPI (m) |
|---|
How the indication is found
Every step is shown so the result can be checked by hand.
1. One unit
The beam is white above the unit's setting angle and red below it. The colour change is not instant but happens over a sector of no more than about 3 arcmin, which this tool treats as a sharp boundary.
2. The bar
The unit nearest the runway has the highest setting and the unit farthest has the lowest. As a pilot descends, the nearest unit turns red first and the farthest turns red last, which gives five indications for four units and three for two units. ICAO labels the units A to D from the farthest, so A is the lowest setting; this tool numbers them from the nearest, so Pos. 1 is the highest setting.
3. Height bands
These are heights above the PAPI's own level at distance d, on a flat approach.
Indications
| Four units | Meaning |
|---|---|
| 4 white | Well above |
| 3 white, 1 red | Slightly above |
| 2 white, 2 red | On glide path |
| 1 white, 3 red | Slightly below |
| 4 red | Well below |
Two units: both white is above, one red and one white is on the path, and both red is below.
ICAO Annex 14 words the four-unit signals as "above" (one red), "further above" (all white), "below" (three red) and "further below" (all red). The labels here, slightly and well, are plain-language equivalents.
Worked example
| Item | Value |
|---|---|
| θ 3.0°, four units, ±30′ and ±10′ | 3.50, 3.17, 2.83, 2.50° |
| On-course band | 2.83° to 3.17°, 20′ |
| Band height at 1,000 m | 49.5 m to 55.3 m |
| Pilot at 3.3° | 1 red, 3 white: slightly above |
| Deviation | +18′, +5.3 m at 1,000 m |
What this tool does not do
It does not model the transition sector, beam cut-off, sensitivity to aircraft eye height or the minimum eye height over threshold, and it assumes a flat approach. Setting values are entered, not hard-coded, so check them against the standard your project follows. For a 3° path ICAO Annex 14 gives four-unit settings of 2°30′, 2°50′, 3°10′ and 3°30′, and two-unit settings of 2°45′ and 3°15′; paths harmonised with an ILS or steeper than 3° use other values, so confirm against the edition you design to.