Learn how to read PAPI lights in a flight simulator, correct a high or low approach, avoid chasing the lights and resolve PAPI/ILS disagreement.
PAPI lights are a row of four red-and-white runway lights that show whether an aircraft is above, on or below the intended approach slope. In a flight simulator, aim for two white and two red, make small pitch-and-power corrections, and continue only while the approach remains stable.
In aviation and real-world flying, PAPI stands for Precision Approach Path Indicator. The units are normally beside the left side of the runway, although some installations are on the right. Each unit projects white light above a defined angle and red light below it; the lamps do not change colour themselves.
What do the four PAPI light combinations mean?
The number of white and red PAPI lights indicates your vertical position relative to the runway's visual approach path, which is often—but not always—about three degrees.
| PAPI indication | Meaning | Appropriate response |
|---|---|---|
| Four white | Well above the path | Increase the descent gradually without diving or exceeding target speed. |
| Three white, one red | Slightly above the path | Make a small correction or allow the path to come back to you. |
| Two white, two red | On the intended path | Hold a stable speed, configuration and descent. |
| One white, three red | Slightly below the path | Reduce the sink rate, normally with a small power increase and coordinated pitch adjustment. |
| Four red | Well below the path | Correct promptly; go around if low, close to the runway or no longer stable. |
The useful memory aid is simple: more white means high; more red means low. A two-unit installation may be an abbreviated PAPI, or APAPI, where one white and one red indicates the correct path. VASI uses a different arrangement, explained in our comparison of PAPI and VASI indications.
How do you follow PAPI lights on approach?
Use the PAPI as a trend indicator alongside airspeed, runway perspective and the aiming point—not as a signal to make abrupt pitch changes.
- Confirm the runway. Make sure the lights belong to the runway end you are approaching. The opposite direction has its own installation or may have none.
- Establish a stable approach. Select the normal landing configuration, target the correct approach speed and align with the centreline before trying to perfect the PAPI indication.
- Read the colour trend. Two white and two red is the target. A momentary change to three-and-one does not require an aggressive correction, particularly in turbulence.
- Correct with pitch and power together. In many light aircraft, power is the main tool for adjusting the descent path while pitch protects airspeed. Aircraft with autothrottle, flight directors or different handling techniques require their normal approved control method.
- Recheck after each correction. Allow several seconds for the new flight path to settle. Reversing every time one light flickers creates an unstable, oscillating approach.
- Go around when necessary. If you cannot restore a safe path without a large correction, or the aircraft is unstable at the applicable stabilisation gate, execute a go-around rather than forcing the landing.
PAPI supplies vertical guidance only. It does not align the aircraft with the centreline, replace obstacle-clearance requirements or authorise descent below instrument minima. Our guide to using the aiming point, runway perspective and visual approach cues covers the rest of the approach picture.
When should you stop following the PAPI?
Stop trying to preserve two white and two red when transitioning into the flare.
The indication becomes very sensitive near the lights because a small height change produces a large angular change. Shift your vision towards the far end of the runway, judge the flare and let the aircraft settle normally. Chasing the PAPI through touchdown can produce a hard landing or an unnecessary pitch change.
PAPI represents the path of the pilot's eye, not the wheels. This distinction matters in large aircraft, where the main landing gear may be far below and behind the cockpit. Real installations account for threshold wheel clearance, but simulator scenery and aircraft eye-point settings do not always reproduce that geometry accurately.
Why might PAPI and ILS guidance disagree?
A small PAPI and ILS disagreement can be normal because their source positions, reference points and approach angles are not necessarily identical.
A large disagreement often indicates the wrong runway, an altered cockpit eye point, inaccurate airport scenery or overlapping stock and add-on scenery. Follow the published instrument procedure during the instrument segment, then use the correct visual references after the runway environment is acquired. If the cues diverge enough to make the approach unsafe, go around.
PAPI is geometric and independent of the aircraft's altimeter setting. Incorrect QNH can still spoil altitude cross-checks and some barometric vertical guidance, so verify it using our simulator QNH setting guidance.
What if the PAPI looks wrong in the simulator?
First rule out viewpoint and scenery problems before assuming your approach is incorrect.
- Return the cockpit camera to the aircraft's normal pilot eye position; an external, drone or vertically shifted view changes the observed PAPI angle.
- Check that you are reading the lights for the correct runway end and not another nearby runway.
- Look for duplicate airport packages or conflicting scenery layers, which can place the runway and PAPI units at different elevations.
- Reduce excessive bloom or exposure if the colours merge into bright white dots. Zooming the view can improve visibility without moving the eye point.
- Cross-check against the runway aiming point and valid instrument guidance. Some default and third-party airports contain incorrectly positioned or calibrated PAPI units.