Runway Awareness and Advisory System (RAAS)

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Article Information
Category:	Safety Nets
Content source:	SKYbrary
Content control:	EUROCONTROL

RAAS

Contents 1 Definition 2 Overview 3 System Description 4 Safety Impact 5 Related Articles

Definition

Runway Awareness and Advisory System

Overview

The Runway Awareness and Advisory System (RAAS) is designed to provide to flight crews with information concerning the aircraft's position relative to an airport's runway while operating at an airport. RAAS is a software upgrade to the later-model Enhanced Ground Proximity Warning Systems and is aimed at reducing the risks of runway incursions.

Runway Awareness and Advisory System uses airport data stored in the EGPWS database, coupled with GPS and other onboard sensors, to monitor the aircraft's movements around the airport with voice announcements at critical points, e.g., "Approaching Runway 09 Left." Other advisory messages include confirmation when the aircraft is lined up on the runway prior to takeoff: for example, "On Runway 09 Right, 4,600 feet remaining." In a scenario where the crew inadvertently lines up on a parallel taxiway and commence a take off, the system provides an aural alert “On Taxiway, On Taxiway” if the aircraft's speed exceeds 40 kts74.08 km/h
20.56 m/s. On approach and after touchdown and roll-out, the system continues to announce the stopping distance remaining to the end of the runway.

System Description

The Runway Awareness and Advisory System (RAAS) offers improved situational awareness for the flight crew in order to help lower the probability of runway incursion incidents and accidents by providing timely aural messages to the flight crew during taxi, takeoff (including rejected takeoffs), final approach, and landing/roll-out operations. Existing EGPWS protection and operation is unaltered by the addition of RAAS.

Advisories/cautions are generated based upon the current aircraft position when compared to the location of the airport runways, which are stored within the EGPWS Runway Database.

The aurals can be grouped into two categories:

• Routine Advisories (annunciations the flight crew will hear during routine operations) and
• Non-Routine Advisories/Cautions (annunciations the flight crew will seldom or perhaps never hear).

RAAS provides the flight crew with five ‘routine advisories'. Three of these annunciations will be heard by the crew in normal operations, providing increased position awareness relative to the runway during taxi and flight operations. They are intended to reduce the risk of a runway incursion. The two remaining ‘routine’ advisories provide information about the aircraft location along the runway, and are intended to reduce the risk of overruns. These advisories are:

• Approaching Runway - In Air advisory provides the crew with awareness of which runway the aircraft is lined up with on approach.
• Approaching Runway - On-Ground advisory provides the flight crew with awareness of a proximate runway edge being approached by the aircraft during taxi operations.
• On Runway advisory provides the crew with awareness of which runway the aircraft is lined-up with.
• Distance Remaining advisories enhance crew awareness of aircraft along-track position relative to the runway end.
• Runway End advisory is intended to improve flight crew awareness of the position of the aircraft relative to the runway end during low visibility conditions.

In addition, RAAS provides the flight crew with several ‘non-routine’ advisories/cautions. These annunciations are designed to enhance safety and situational awareness in specific situations not routinely encountered during normal aircraft operations. Some of the RAAS advisories include distance information. The unit of measure used for distance can be configured to be either metres or feet.

• Approaching Short Runway - In-Air advisory provides the crew with awareness of which runway the aircraft is lined-up with, and that the runway length available may be marginal for normal landing operations. If desired, an additional caution annunciation can be enabled which provides the crew with awareness that the issue has not been resolved when the aircraft is on final approach.
• Insufficient Runway Length - On-Ground Advisory provides the crew with awareness of which runway the aircraft is lined-up with, and that the runway length available for takeoff is less than the defined minimum takeoff runway length. If desired, an additional caution annunciation can be enabled which provides the crew with awareness that the issue has not been resolved when the aircraft is on the final stage of takeoff.
• Extended Holding on Runway advisory provides crew awareness of an extended holding period on the runway.
• Taxiway Take-Off advisory enhances crew awareness of excessive taxi speeds or an inadvertent take-off on a taxiway. If desired, this function can provide a caution annunciation in lieu of an advisory annunciation.
• Distance Remaining advisories provides the flight crew with position awareness during a Rejected Take-Off (RTO).
• Taxiway Landing alert provides the crew with awareness that the aircraft is not lined up with a runway at low altitudes.

Safety Impact

According to EUROCONTROL, the potential for aircraft related systems (moving maps and runway awareness and advisory systems such as RAAS) to reduce the number of runway incursions depends upon the level to which the fleet that operates at an airport is equipped. In the short and medium term the level of equipage will be low and therefore the influence on runway incursion risk (as seen from an airport perspective) will be negligible. If all aircraft were fitted, the runway incursion reduction that could be achieved has been estimated in the order of 6-10%.

Related Articles

RI

• Runway Incursion;
• A-SMGCS;
• Aerodrome Runway Incursion Assessment Tool
• Flight Operations Risk Assessment Checklist - Active Runway Crossing;
• Accident and Serious Incident Reports: RI;

RE

• Runway Excursion;
• Wrong Runway Use;
• Accident and Serious Incident Reports: RE