What is RAAS? The Runway Awareness and Advisory System explained
RAAS is the cockpit system that tells airline pilots, out loud, where they are relative to the runways around them. It exists to stop three kinds of accident: runway incursions, takeoffs and landings on taxiways, and runway overruns.
RAAS in one paragraph
The Runway Awareness and Advisory System (RAAS) is a Honeywell function of the Enhanced Ground Proximity Warning System (EGPWS). It compares the aircraft position from GPS with a database of airport runways, and gives the crew short spoken advisories, such as "Approaching two five left" or "On taxiway", at the moments where a wrong runway or a wrong turn is most likely. Many airliners carry it. Later Honeywell options (SmartRunway and SmartLanding) add further alerts, such as unstable approach monitoring.
Why RAAS exists
Many runway incidents do not involve a lack of flying skill, but a crew that is not where they think they are: entering a runway they were not cleared for, lining up on a parallel taxiway at night, or landing on a runway shorter than expected. RAAS adds an independent voice in the cockpit that confirms the obvious when things are right, and speaks up when they are not.
- Runway incursions: a call every time the aircraft approaches or enters a runway, with the runway designator.
- Taxiway takeoffs and landings: a caution when the aircraft accelerates, or is about to land, somewhere that is not a runway.
- Runway overruns: distance remaining calls and short runway advisories. Predicting an overrun is a separate function, Runway Overrun Prevention.
Routine and non-routine advisories
RAAS keeps quiet most of the time. Routine advisories confirm normal situations, like the runway you are approaching while you taxi, and play at a lower volume. Non-routine advisories and cautions flag something unusual, such as being on a taxiway at takeoff speed, and are louder and more urgent. Some aircraft also show the message as text on the primary flight display or navigation display.
Typical RAAS callouts
| Advisory | When | Example |
|---|---|---|
| Approaching runway (on ground) | Taxiing towards a runway holding point | APPROACHING 25 LEFT |
| On runway | Entering or lining up on a runway | ON RUNWAY 25 LEFT |
| Takeoff on taxiway | Accelerating on a surface that is not a runway | ON TAXIWAY! ON TAXIWAY! |
| Short runway (on ground) | Lining up on a runway shorter than a configured minimum length | ON RUNWAY 25 LEFT, 1400 METERS REMAINING |
| Extended holding on runway | Holding in position for a long time | ON RUNWAY 25 LEFT. ON RUNWAY 25 LEFT. |
| Distance remaining | Rejected takeoff, landing and rollout | 1000 … 500 … |
| Approaching runway (airborne) | On final approach, lined up with a runway | APPROACHING 25 LEFT |
| Taxiway landing | On approach, not lined up with any runway | CAUTION TAXIWAY! CAUTION TAXIWAY! |
| Unstable approach (SmartLanding) | Too high or too fast on final | TOO HIGH, TOO HIGH |
RAAS and Runway Overrun Prevention
RAAS tells you how much runway is left. Runway Overrun Prevention (ROP) goes one step further: it predicts where the aircraft will stop and warns before the runway runs out. Read more in Runway Overrun Prevention explained.
RAAS in Microsoft Flight Simulator
Default and most add-on aircraft in MSFS do not simulate RAAS. vRAAS² adds it to every aircraft in Microsoft Flight Simulator 2024 as an in-sim module: runway entry and approach callouts, distance remaining, taxiway and short runway cautions, unstable approach warnings and runway overrun prevention, configured from an EFB app in the cockpit.
vRAAS² is an independent simulation add-on and is not affiliated with or endorsed by Honeywell, Airbus or Boeing. Honeywell, EGPWS, Airbus, Boeing and other names mentioned are trademarks of their respective owners.