RAS vs. RIS (Radar Information/Advisory Service)

[galleypower]

Dear Controllers and other knowledgable people,

Could someone briefly explain me the difference of Radar Information Service (RIS) and radar Advisory Service (RAS)?
And where is RIS mainly used? In airspace where MIL planes and CIVIL planes share the airspace?
As far as I know, RIS only gives you info about other aircraft in the area, but avoidance is up to the pilot and RAS gives you 'full' service, incl. avoidance instructions.

Thanks for your help.
Cheers, galleypower

[Carbide Finger]

You've answered most of your questions yourself!

RIS - Just the traffic info
RAS - Traffic info and avoiding action

Both services can be offered outside of controlled airspace. The controller will generally ask what service the aircraft is requesting. The controller then makes a decision on whether they have the capacity to give the A/C a RAS or whether they will only give it a RIS.

Other things for the controller to consider are Radar Coverage, traffic levels (his own and A7000 doing their own thing) and likelyhood that they will be able to give the same service in the future.

I, as an LACC controller, very rarely give a full RAS. The Military will give the service the aircraft requests (so I believe). I will also limit my service to transponding traffic only as I am using multi radar.

Hope this helps

CF

[Inverted81]

Just as an addition, for an aircraft to receive a RAS they have to be able to accept vectors that MAY take them into IMC, so generally only IFR a/c outside controlled airspace will request a RAS...
81

[TATC]

Just as an addition, for an aircraft to receive a RAS they have to be able to accept vectors that MAY take them into IMC, so generally only IFR a/c outside controlled airspace will request a RAS...
81

in fact RAS is only available to IFR flights - VFR can only get a RIS

[funfly]

in fact RAS is only available to IFR flights - VFR can only get a RIS
Are you sure about that?

[Stupendous Man]

Yup

RAS is for IFR only

RIS can be given to IFR or VFR

[PPRuNe Radar]

Funfly

Affirm, RAS only available to IFR flights.

Full AIP ENR info below:

3.1 Radar Advisory Service (RAS)

3.1.1 RAS is an air traffic radar service in which the controller will provide advice necessary to maintain prescribed separation between aircraft participating in the advisory service, and in which he will pass to the pilot the bearing, distance, and, if known, level of conflicting non-participating traffic, together with advice on action necessary to resolve the confliction. Where time does not permit this procedure to be adopted, the controller will pass advice on avoiding action followed by information on the conflicting traffic.

Under a RAS, the following conditions apply:

(a) The service will only be provided to flights under IFR irrespective of meteorological conditions;

(b) controllers will expect the pilot to accept vectors or level allocations which may require flight in IMC. Pilots not qualified to fly in IMC should accept a RAS only where compliance with ATC advice permits the flight to be continued in VMC;

(c) there is no legal requirement for a pilot flying outside Controlled Airspace to comply with instructions because of the advisory nature of the service. However, a pilot who chooses not to comply with advisory avoiding action must inform the controller. The pilot will then become responsible for initiating any avoiding action that may subsequently prove necessary;

(d) the pilot must advise the controller before changing heading or level;

(e) the avoiding action instructions which a controller may pass to resolve a confliction with non-participating traffic will, where possible, be aimed at achieving separation which is not less than 5 nm or 3000 ft, except when specified otherwise by the regulating authority. However, it is recognised that in the event of the sudden appearance of unknown traffic, and when unknown aircraft make unpredictable changes in flight path, it is not always possible to achieve these minima;

(f) information on conflicting traffic will be passed until the confliction is resolved;

(g) the pilot remains responsible for terrain clearance, although ATSUs providing a RAS will set a level or levels below which a RAS will be refused or terminated.

3.2 Radar Information Service (RIS)

3.2.1 RIS is an air traffic radar service in which the controller will inform the pilot of the bearing, distance, and, if known, the level of the conflicting traffic. No avoiding action will be offered. The pilot is wholly responsible for maintaining separation from other aircraft whether or not the controller has passed traffic information.

Under a RIS, the following conditions apply:

(a) The service may be requested under any flight rules or meteorological conditions;

(b) the controller will only update details of conflicting traffic, after the initial warning, at the pilot's request or if the controller considers that the conflicting traffic continues to constitute a definite hazard;

(c) the controller may provide radar vectors for the purpose of tactical planning or at the request of the pilot. However, vectors will not be provided to maintain separation from other aircraft, which remains the responsibility of the pilot. There is no requirement for a pilot to accept vectors;

(d) the pilot must advise the controller before changing level, level band or route;

(e) RIS may be offered when the provision of RAS is impracticable;

(f) requests for a RIS to be changed to a RAS will be accepted subject to the controller's workload; prescribed separation will be applied as soon as practicable. If a RAS cannot be provided the controller will continue to offer a RIS;

(g) for manoeuvring flights which involve frequent changes of heading or flight level, RIS may be requested by the pilot or offered by the controller. Information on conflicting traffic will be passed with reference to cardinal points. The pilot must indicate the level band within which he wishes to operate and is responsible for selecting the manoeuvring area, but may request the controller’s assistance in finding a suitable location. The controller may suggest re-positioning on his own initiative, but the pilot is not bound to comply;

(h) the pilot remains responsible for terrain clearance. ATSUs providing a RIS will set a level or levels below which vectors will not be provided, except when specified otherwise by the regulating authority.

[foghorn]

Think of a RAS as being a bubble of Class F airspace around an aircraft, 5nm in radius and 3,000ft above and below an aircraft's level.

The bubble follows the aircraft as it flies through Class G - the aircraft is given traffic information and advisory vectors or level changes to maintain separation from any traffic that enters its little bubble of Class F.

In the case of unknown traffic, the controller will seek to avoid it by 5nm/3000ft, due to the possiblity of sudden deviations of the unknown contact. In the case of known traffic, standard separation is enough (5nm/1,000ft).

It's not written that way in the legal documents (the bubble of class F doesn't actually exist), but it's a way of thinking about it.

(edit: crossed with Radar's chapter and verse)

[chevvron]

Foghorn ; don't forget that where approved by the CAA, horizontal separation may be reduced to 3nm between identified aircraft working the same unit, and the RAF are usually allowed to use reduced vertical of 500ft between identified traffic.

[NorthSouth]

I, as an LACC controller, very rarely give a full RAS. The Military will give the service the aircraft requests (so I believe). I will also limit my service to transponding traffic only as I am using multi radarBut isn't your multi radar primary as well as secondary? Or do you normally not display the primary?
NS

[Spitoon]

Foghorn ; don't forget that where approved by the CAA, horizontal separation may be reduced to 3nm between identified aircraft working the same unit, and the RAF are usually allowed to use reduced vertical of 500ft between identified traffic.chevvron; read the rules that PPRuNe Radar was good enough to post.

Anyway, good luck to galleypower. Either understanding the mess that the UK gets itself into by not following ICAO SARPs .... or with the interview!

[chevvron]

Spitoon - don't understand you. Prune radar dosen't mention reduced separation; in any case I was embelishing to Foghorn's remarks.

[TATC]

Spitoon - don't understand you. Prune radar dosen't mention reduced separation; in any case I was embelishing to Foghorn's remarks.

actually he did - he mentioned 3000ft or 5 miles, except where authorised by the CAA. As the 3 miles minmum radar separation usd by APR units is also subject to authorisation by the CAA it is covered by this statement

[DONer Kebab]

But isn't your multi radar primary as well as secondary? Or do you normally not display the primary?
NS

I have absolutely no idea why CF would limit a RAS to transponding aircraft only due to operating with a multi-radar picture. The picture contains both primary and secondary information with readily identifiable symbology to tell you whether a target is being painted by either primary or secondary radar only, or combined. That's why military controllers can offer the full RAS.

[Spitoon]

My point is that RAS requires 5 miles/3000ft - if you can get it - unless the CAA authorises something less for the purposes of RAS. Reduction in separation standards between identified targets working the same unit are something completely different. Even if you are allowed to use 3 miles radar separation, unless the MATS 2 says otherwise in relation to RAS, you've still got to aim for 5 miles when giving a RAS.

[TATC]

I have absolutely no idea why CF would limit a RAS to transponding aircraft only due to operating with a multi-radar picture. The picture contains both primary and secondary information with readily identifiable symbology to tell you whether a target is being painted by either primary or secondary radar only, or combined. That's why military controllers can offer the full RAS.


There are certain sectors that use radar feeds from more than one radar, providing a composite picture on the tube. I think that in thses situations then increased separation at the seem between radar feeds is required. I think that this might be what CF meant by multi radar

[DONer Kebab]

TATC

I would agree if we were talking about a composite radar picture, as used at West Drayton, that uses 2 individual radar sources to cover different parts of the display - that has a seam and implications for control close to it. However, the multi-radar picture at LACC is a true 'mosaic' picture with no seams, providing both primary and secondary radar information, depending on the best returns received from the contributing radar sources.