ILS Category - ILS Performance Classification
 

Hello guys,

I have a question regarding the promulgation of ILS status to cockpit crew members. Currently we (ILS procedure designers at ATC) are having a discussion with our national regulator about the promulgation of the ILS status. Our regulator is asking us to stop informing the cockpit crew by means of NOTAM or on Radio Telephony about the supported ILS CAT (CAT I / II / IIIa or IIIb). We should only promulgate the current ILS Performance Classification in our AIP or by means of NOTAM in case of Performance degradation. It is a crew responsibility they say. This ILS Performance classification looks like III/E/3 of II/T/2. It is giving information about maximum system category / point of coupling auto pilot / and integrity. In some cases a runway ILS system is downgraded to II/T/1 which actually means in operations only an ILS CAT I can be flown.

My question is how familiar are aircrew from around the world with this ILS Performance Classification (coming from Annex 10 I believe)? We want to avoid discussion about the supported category on the frequency.

I know some airlines are publishing conversion tables. But it doesn't look to me like a pragmatic solution.

Hoi Peter Pan,

Usually the charting companies (Jeppesen, LIDO etc) state the highest category on their charts. So we as pilots know the system is capable of let's say CATIII.

If there is no NOTAM saying the system is degraded then in low visibility situations we expect on the ATIS promulgated "low vis operations".

I hope this answers your question?

You would need to let folk know via NOTAM that the ILS was down cat for flight planning purposes.

If you didn't it would play merry hell with diversion planning etc.

I haven't heard of this ILS pref classification BTW but thats not to say the pilots who fly CIII don't have it in there training.

Cat I, II, III a,b,c and what else?
 

The only ILS classification I know is CAT I, II or III a, b (and c)
I didn't/don't know about other ILS classifications. Please enlighten me. :ok:

I will look at the published airport charts and the notams to know the status of a particular ILS. In the absence of notams, I will suppose that the ILS is performing as published as soon as I hear the ATIS or ATC telling me that low vis ops are in progress. Only if the ILS is not performing as published would I like to be informed about that by notam or atis (and/or atc).

Is this what you wanted to know about my (lack of) knowledge?

Never heard of it before (and flown into AMS many times in crap weather :ooh:).

At your friendly neighbourhood airline we have such a conversion table in the "Quick Reference Pages", so easily looked up in flight. This table has 11 possible ILS classifications (from I/A/1 to III/E/4). The CAT III section alone has 8 sub-classifications. Some allowing operations down to CAT I minima, some to CAT II and others to CAT III minima. I know that doesn't sound logical, but while the "Facility Performance" (the first character) may be CAT III, the "Level of Integrity" (the third character) may restrict ops to e.g. CAT I. The second character, by the way, denotes the "Limit of Course Structure", whatever that may be.
Even when CAT III ops are authorized, distinctions are made between CAT IIIB with DH and without DH, and for the RVR limits to be used.

Long story short: just telling pilots that "the ILS supports CAT III operations" is definitely not telling the whole story.

And re. pragmatic: works fine for us!

The "Limit of Course Structure" tells you something about to point until which the autopilot can coupled as far as I understood. Letter E for example represents roll out guidance.

@MoodyBlue: I am aware of the Quick References Pages of some of our local airlines but it is concerning me that a lot of operators are not aware of this ILS performance class. Until a few years ago ATC was only informing pilots of the supported category. And ATC determined (they are technical owner of system) which category was supported (based on the III/E/2 for e.g.). So what actually happened is that this check shifted (or is shifting) from ATC to the cockpit (sounds like a liability issue).

Reading the reactions on this topic I am still concerned that at the moment we stop with sending this supported category on ATIS we get discussions on the frequency.

Thx for your reactions till so far:ok:

Sorry PeterPANOP, looks like everyone so far has misunderstood your question.

ILS classification has recently been thrown into the spotlight as a result of the introduction of Lower than CAT l and Other Than CAT ll approach operations.

In the UK there are some installations that can't meet integrity targets and so need to be upgraded. Somewhere on the web will be the requirements. At any airport with an ILS there should be a person nominated as responsible for NAVAIDs. In the UK they are known as SATE.

As far as I know up till recently the type of classification you refer to has not been something operators have not had to take account of.

Suggest talking to NATS at Swannick - there should be an engineering dept to help you.

SGC

So instead of someone in a warm tower/control room with all manner of reference manuals on a desk which they can spread them out and nothing else pressing and they only have to do it once for any given change in circumstances. And we can presume well rested and have multiple people to check it.

They want to move it to, passing the buck to two people working it out while flying an aircraft and setting up for a landing in crap conditions.

Work load includes flying the aircraft, monitoring the aircraft, briefing the approach, setting up for possible divert with not alot of fuel to spare. They may be at the end of a 12 hour day and in the middle of the night according to thier body clock.

Then they have to find the reference card work it out and then figure out what this actually means for there planned approach. And then repeat if it changes half way through the approach while doing all the other good stuff like checklists and flying the plane etc.

And of course every aircraft is going to have to do it. How many an hour with the potential to get it wrong is that?

Then you will get all the none locals some of which only operate into Europe maybe 1-10 times a year who won't be current and won't have a clue what it means.

What a cracking idea, really going to improve flight safety that little gem.

I am struggling to understand the OP's point/question. From the point of view of the ground equipment there is only CATI, II, IIIA, B & C. I am not aware of there being any other subclassifications as mentioned by the OP taking into account various other factors that are not pertaining to the capability of the ground system, e.g. autopilot capability etc. Aircrew will already be fully aware of the capability of their aircraft/avionics and how that affects thir ability to fly published procedures and with the specified minima.

Here in the UK (and everywhere else IIRC) any reduction in ILS CAT will already be published both by NOTAM and broadcast on the ATIS. Aircrew, ATC and Tels will already be fully aware of ILS CAT and the related minima at any given time anyway, so I don't understand the point being made here - there wouldn't be any need to discuss the ILS capability on RT if its already known, surely? I have never heard ATC or Aircrew discussing this on-air before.

Smithy