Limited Radar Information Service

[Mooncrest]

Can any ATC professionals tell me if there is an official definition of this term ? I hear it frequently from my local ATC unit, where it's sometimes qualified with the addition of 'limited to transponding aircraft only', 'limited due to altitude' or 'limited due to high ground/terrain'. Being a non-ATC person, I would have thought that RAS and RIS were absolute services, i.e. the pilot either gets the service or he/she doesn't, without conditions being applied by the radar controller.

All replies, rebukes etc. gratfeully read and digested.

Thankyou.:ok:

[Warped Factor]

From the Manual of Air Traffic Services Part 1 (available for download from the CAA website)...

Limiting a Service

1.6.1 Outside controlled airspace in circumstances where controllers cannot continue to provide the following primary requirements:

a) traffic information and traffic avoidance in respect of all conflicting unknown aircraft for a radar advisory service; and

b) traffic information in respect of all conflicting unknown aircraft for a radar information service, controllers may elect to continue to give the service by limiting the extent to which it is provided.

1.6.2 Controllers must inform pilots when they limit the service and ensure that pilots are made fully aware of the implications of any limitation.

1.6.3 In particular the service should be limited when:

a) the aircraft is operating within 10 miles* of: i) the edge of the radar display; ii) weather clutter; or iii) permanent echoes.

b) the aircraft is operating in an area of high traffic density;

c) the aircraft is operating near to the limits of solid radar cover; or

d) The service is being provided using secondary radar only.

* Except where the range selected (e.g. 3, 10, 15 miles) will not enable these criteria to be met during an approach to an aerodrome.

WF.

[Evil J]

I have certainly been using this a lot recently at my unit, limiting to SSR traffic only as the primary radar is AWFUL...cant see aircraft inside controlled airspace never mind outside!!

[Bern Oulli]

And continuing from Warped Factor's neat extract from the MATS Pt 1:
Scenario: Scrugg's Wunderplane (with the go-faster stripes) pootling along at 3000 ft 30 miles S of the radar unit and requesting a RAS/RIS (it matters not). At that range and altitude he is probably bumping along the bottom of the radar cover, certainly the primary radar cover. Therefore the radar is likely to have difficulty seeing other targets at similar altitudes, especially if they are further away. The sort of phraseology you might expect from the controller in this circumstance would be:
"Limited RAS/RIS, little or no warning of traffic from below or from the South." If not too busy the controller might add, by way of an explanation, "... due to your proximity to the limits of my (radar) cover", but it is all rather a mouthful when surrounded by Indians.

[EmergingCyclogenesis]

I've never liked the amount of "limitations" that go on. It is almost like a cop-out and absolving any responsibility for the controller. Unfortunately, in these days of corporate and individual liability, most controllers feel compelled to issue such a statement, to get it on the tapes, just in case something happens. The whole idea was to provide a simple way of informing pilots of equipment deficiencies or that they were close to the base or limits of cover.

Trouble is, it gets used as a safety net...2 aircraft in the way and your service gets limited due to high traffic density!!!

[ayrprox]

genesis,

If I am limiting a service im not doing it because its a cop out i'm doing it for a reason. Against transponding a/c only, i'm using an ssr only no primary, limited due to altitude, you are a long way from the radar head and i'm not going to be able to give you much warning from aircraft below or behind . limted due to traffic then there will be a significant number of aircraft, or highly complex situation, not to make things easy on ourselves.
In this way you know where you stand and exactly the service i'm providing. If i say RIS you would expect a certain level of service, if that service is limited for whatever reason then we are both singing from the same hymn book and both know what service to expect.

[cdb]

Same as Ayrprox

If I say RAS/RIS that implies I can provide notice in good time of pretty much anything that comes near you. If I limit the service, it'll be for a good reason, which I'll state immeadiately after eg.

"Limited RIS due base of cover"
ie. I won't see stuff climbing underneath you because the radar has a base of cover that gets higher as you get further away from the radar head

"Limited RIS: Information on transponding A/C only"
Some parts of certain sectors only have SSR cover, so I can't see primary only contacts.

Its self-explanatory really, just listen to what the controller tells you!

[moony]

First of all, I am military - or was till Jan this year! So not sure about civilian phraseology.
What I don't follow is why controllers are saying the service they are giving is a "limited RAS/RIS". In my view, the service is RAS/RIS but that there is "LIMITED TRAFFIC INFORMATION due to........." . By stating the service, then applying a limitation and giving the reason why, surely that gives the customer a fuller picture.
moony

[Evil J]

I think we are arguing over semantics here now. If its "limited traffic information" then surely the service you are providing is limited, ergo "limited radar information service" seems about right to me?? Either way the MATS 1 is quite clear on the phraseology

[Tinpot Radio]

I personally just say "Limited RIS (never ever RAS so don't ask!) due to radar performance" for two reasons. Firstly to cover my back if something gets missed and secondly so that pilots know that I am not an all seeing god of the skies and continue to keep their eyes open.

I agree that often you can only call traffic on transponding aircraft, mainly due to modern over processed and filtered radar displays that are not designed for ATSOCA provision.

If equipped, I think you guys should all actively squawk 7000 outside controlled airspace even if you are not interested in talking to ATC, as it makes ATSOCA provision much easier and thus safer. And wouldn't you just hate to crash into a swanky £6 million helicopter because his TCAS is useless if you are not transponding in your C150?

Tinpot.

[EmergingCyclogenesis]

Moony is quite correct in what he says. You do not limit the service you are providing, you emphasise that traffic info is limited due to the reasons you have all stated.

Tinpot has clearly backed up my statement by saying

Firstly to cover my back if something gets missed and secondly so that pilots know that I am not an all seeing god of the skies and continue to keep their eyes open.

[Vino Collapso]

Still sounds like ' the busier it is and therefore the more you need a service, the less likely you are to get one'

Nothing against the guys and gals trying to provide the service, they are just working with the tools they are given. But there must be a solution whereby the busier the airspace the higher the degree of protection provided.

[Don't Tell Him Pike]

But there must be a solution whereby the busier the airspace the higher the degree of protection provided.

There is, it's called Controlled Airspace!

[ayrprox]

Pike just beat me to it.
If the airspace is sufficiently busy particularly with commercial traffic then controlled airspace can improve matters though not always.
in an ideal world we would like to upgrade when busy, but this also increases the chance of missing something and also reduces the number of a/c that a controller will handle before he actually will not provide a service at all to any new arrivals.
it also depends on the airspace. I work a sector with controlled,advisory, and class G. in this situation i'm afraid there is a pecking order. if i am busy with controlled airspace traffic there is no way i'm going to give class G traffic my undivided attention so i'll limit any service or downgrade it, even cancel the service.
i'll take genesis point on board about us covering our backs, but unfortunately we live in a progressively litigious(apologies for spelling if wrong) society and management within our industry is showing more signs of covering their @sses therefore we must do the same. I think uberlingen showed the ultimate price paid by both controller, passenger and pilot when mistakes are made (note NOT management).
However genesis said
Trouble is, it gets used as a safety net...2 aircraft in the way and your service gets limited due to high traffic density!!!.
sorry genesis but unless you're sitting infront of that radar mate you dont have the full picture and have no idea how hard the controller is working.there may be long pauses on the r/t but the controller may be on the phone coordinating , or struggling with 7 across in the crossword:E

[Vino Collapso]

There is, it's called Controlled Airspace!

Nah, thats the one where if it gets busy you slap on flow control to quieten it down again :O

Obviously every system has its maximum capacity and no one expects the workers to exceed that, but an information service, be it RIS or FIS where separation is not required to be provided must have a greater 'maximum capability'.

:(

[Mooncrest]

Thankyou for all your replies ladies and gents. I'm slowly digesting it all and quite a hornets' nest it is too !

[EmergingCyclogenesis]

sorry genesis but unless you're sitting infront of that radar mate you dont have the full picture and have no idea how hard the controller is working.there may be long pauses on the r/t but the controller may be on the phone coordinating , or struggling with 7 across in the crossword

That's a bold statement Ayrprox...I may well be your Watch Manager and commenting on your standard of control! By the way, you were not doing the crossword, you were reading OK magazine.

;) ;) ;) :ok:

[CAP670]

Although it might sound like semantics, it's actually essential as information to the participating pilot(s) who in effect, enter into a contract with ATC.

However, what civil radar ATCOs really ought to add is the qualifier used by their military colleagues who are (as regards most terminal [airfield] units) the UK Class G/ATSOCAS experts:

"Limited Radar Information (state reason[s]) - late warning of traffic from (state area/segment/above/below)."

In respect of Radar Advisory "Limited Radar Advisory (state reason[s]) - standard separation may not be achieved."

But beware! In these litigious times, ATCOs retain a Duty of Care that can supplant anything that's written in MATS Part 1, MATS Part 2, JSP552, Controllers' Order Book, etc., and so even under RIS whether Limited or not, 'Traffic Avoidance Advice' can be a necessary option if only to cover your own six o'clock...

:suspect: