Proposed amendment of the ANO: Mode S

[Aunt Rimmer]

Originally Posted by Jumbo Driver[B

Aunt Rimmer[/B], I understand your arguments about the benefits from ACAS but I think you (and some others on this thread) are overlooking one thing. It is not necessary to fit Mode S to provide the necessary response for Johnny Tornado's ACAS to see and avoid you with an ACAS RA. It is only Mode C that is needed - so you only need to fit Mode C to enjoy the benefits you describe above in Scenario 2. As I understand it, there is no enhancement to another aircraft's ACAS RA from you carrying Mode S, rather than Mode C.
Mode S is a totally unnecessary addition for most GA aircraft as they are not capable of providing the additional Air Data feeds such as TAS, heading, or datalink capability that Mode S can utilise. For such aircraft, the only "benefit" that I can see is that the aircraft identification is provided to ATC in the SSR response.
JD

I agree Mode C is all that is required - I was using Mode S as the example because
a) I don't have Mode A/C at the moment so IF I have to install a piece of kit under legislative duress it will be Mode S.
b) all the CAA talk/spin is about Mode S, so I think it better to use that as a counter.
But, yes, you are right.
One other thought - how is anyone (in the air or on the ground) going to know if the altitude info displayed by Mode S (or Mode C for that matter) is actually correct? Particularly in respect of non radio or aircraft not receiving any service ?
I am sure this will apply to the majority of flights in Class G, because the ATC system could not cope if everyone called up a radar unit to have their mode C/mode S verified....... now there's a thought

[slim_slag]

Originally Posted by bookworm

So what you mean is that pilots of TCAS-equipped aircraft will now be given collision avoidance instructions for against others potentially on a collision course with them, where previously they wouldn't have seen them at all?

Well yes, but the current assumption is that non-mode S aircraft remain clear of the airspace that the TCAS aircraft is in. So separation is 'guaranteed'. What appears to be driving this is a desire for TCAS-equipped aircraft to enter non CAS. This is no doubt driven by the desire of airlines to make more money, and the way it is being proposed means the GA community are paying to install equipment which will provide GA negligible benefit, and for some even make it impractical to continue to fly. It's an airspace grab in another guise, being funded by the guy in his spamcan.

[jabberwok]

IO540 - if you can't understand that flying 'blind' without knowing what else is around is dangerous, then I query your airmanship and judgement. You don't need 'supporting evidence' to support what something which is fundamentally axiomatic. Rely on statistics and you may well become one yourself.

I bet you never flew with Loganair then..

Stornoway, Benbecula, Tiree, Islay, Campbeltown, Londonderry. Absolutely crammed with airways to choose from and radar controllers begging to talk to you.

Beagle must be aware that his views are, in some parts of the UK, a theoretical ideal rather than a practical reality. No doubt he would like me to rip out the IAP's in my manual for all those airfields without radar cover.

[tmmorris]

I'm sorry, BEagle, because I usually agree with you, but I'm afraid that as IO540 says, IFR OCAS with only a FIS (if that) is routine in some parts of the UK. There's no getting around it. I don't do it regularly now, as it's against our club SOPs, but even then it is sometimes unavoidable; as IO540 says, what are you supposed to do when 'dumped' by a LARS unit without anyone else to talk to? And even when all goes according to plan, you can find you have 5-10 minutes between being handed off by one controller and being visible on radar to the next. A couple of examples:

an OCAS IFR flight EGUB-EGXE: East Midlands couldn't pick me up initially even though I was at FL30 and requesting a climb to FL50;

an OCAS IFR flight Shobdon to EGUB; after departing Shobdon and climbing into IMC Gloucester couldn't pick me up until about 10 minutes out from Shobdon.

In both cases there was nothing I could do but sit tight and wait for radar cover.

What's stopped IO540 crashing is indeed the 'big sky' theory (plus the IFRs, of course, which were designed precisely with this in mind). As he says, there just isn't the evidence to back up your claim - mid-airs just don't happen like this. Far more dangerous are VFR mid-airs in the vicinity of airfields, or IFR CFIT incidents, neither of which are solved by radar cover.

Tim

[BEagle]

It'll take just one mid-air under such circumstances and the IMC-outside-CAS-without-radar big-sky-theory risk takers will probably find the rules changed. Particularly if the pieces of aeroplane and human raining down from the sky did so over a populated area.

I suspect that the only reason it isn't already banned is that NATS know full well that they haven't got the infrastructure to cope with providing full radar service outside CAS. Additionally, more and more military aerodromes have closed over the years, reducing LARS cover substantially.

IMC outside CAS without RIS or RAS is specifically banned under my Club's Flying Order Book as well.

Out of interest, what was the cloudbase when you left Shobdon?

[smarthawke]

The only 'monthly' mag to cover this saga I've seen recently is the present (September) 'Today's Pilot' - both in the editorial and in a stand-alone article. Interesting info and points made.

Now do I invest in a new transponder now (it's started to play up but Day-VFR use only) or wait a while? Me thinks I'll wait a bit longer....

[robin]

Originally Posted by BEagle

Additionally, more and more military aerodromes have closed over the years, reducing LARS cover substantially.

When I went to FFF last weekend I spoke to a CAA rep who suggested that all aircraft would always be talking to a radar controller or at least a LARS service.

So if the CAA don't understand the limitations on some of the LARS stations (not at weekends and not after 4.00pm) or the growing gaps or the times they ask you to go away, then what are they doing proposing this RIA

What possible use is it to aircraft not receiving a radar service.

[Sedbergh]

One feels very tempted to try to organise an "everybody in the air request RIS at once" event to demonstrate to the CAA what could happen with their Mode S proposal.

But since a very limited number of people rely on RIS for real and trying to fuse the system would be irresponsible, I won't.

I was in a thermal with 10 other gliders a couple of weeks ago. Do you suppose Mode S and LARS/RIS could have maintained separation?

[mm_flynn]

Originally Posted by BEagle

It'll take just one mid-air under such circumstances and the IMC-outside-CAS-without-radar big-sky-theory risk takers will probably find the rules changed. Particularly if the pieces of aeroplane and human raining down from the sky did so over a populated area.

BEagle,
Mid-airs happen and the rules aren't suddenly changed. They are reviewed to see if the balance of risk is correctly assessed.

Some times they result in rule changes like the Ceritos Crash that brought Mode C veils to the US terminal areas, or the airliner/airliner mid-air over the Grand Canyon that brought class A airspace above FL180 in the US.

Sometimes they result in a review and no change (the periodic GA/GA or GA/Mil mid airs in VFR) or international standardisation of crew responses (two airlines with ACAS under Radar Control in Germany).

The complexity of changing the UK airspace, regulation, infrastructure, etc. to move to an environment where ATC service (could be procedural or radar) is required to fly IMC in Class G is enormous. It would have to be a spectacular incident - and more likely would result in regulation or SOP for the airlines not to fly outside Radar Coverage in Class G.

Now anyone equipped to fly IFR who is trudging along in IMC not receiving a Radar Service AND not squawking (ideally Mode C/S) is taking totally unnecessary risks - unless they are a glider

[BEagle]

On a different note, are the military to be exempted from this 'Mandatory Mode S' proposal?

If so, then why?

[robin]

Yep

They are trialling it in some of the fleet, but basically FJs won't be fitted

[tmmorris]

To be honest, I can't remember - it was a couple of years ago. I'd come down VFR (scud-running) from Sleap and wasn't happy doing that really in an area with so many mountains, hence the decision to go back IFR. I seem to remember the scud-running was at about 1500' AMSL which means the cloudbase would have been c. 1200' AAL. With hindsight I could have scud-run until Gloucester picked me up, but I'd entered IMC before QSY-ing from Shobdon so I was stuck with it...

It's all very well having club rules (this was actually before I joined my current club anyway) but they are meaningless when as IO540 says you are dumped with 'squawk 7000, freecall enroute, good day'.

Tim

[jabberwok]

They are trialling it in some of the fleet, but basically FJs won't be fitted

The trial is quite extensive with approx 180 aircraft so far equipped. FJ's do indeed seem to be exempt but a couple of Tornado's have been picked up sending Mode S codes.

[BEagle]

That would mean a cloudbase of about 2300 ft amsl?

Hmm - safety altitude on that leg is....?

IMC below safety altitude and without radar? I think I'd sooner have flown at around 1800 ft QNH under VFR.

I guess all the military's civil-registered Tutors and Vigilants won't be exempt from the Mode S proposals then?

[tmmorris]

Not sure how you worked that out - as I said, cloudbase was c. 1500ft amsl, or 1200ft aal. I was only below MSA for the time required to climb (over the flat terrain to the east of EGBS) to my cruising altitude/FL. Believe me, I'd have been happy at 1800ft VFR too. But with a cloudbase at 1500ft I decided I would be safer IFR in IMC - and expected to get a radar service sooner.

I'm not saying I did the right thing - just that sometimes, as then, IFR OCAS without radar service is unavoidable at the moment. Of course, it would be great if radar cover was universal. But it ain't.

Particularly irritating on that trip is that NATS has a radar head near Gloucester but because they are privatised, they don't supply Gloucester with the feed - and Gloucester can't afford to pay for it. Gloucester is primary only - with SSR they could probably have given me a radar service immediately after I left Shobdon.

Tim

[bookworm]

I'm not saying I did the right thing - just that sometimes, as then, IFR OCAS without radar service is unavoidable at the moment.

Of course you did the right thing. Not only is there a greater risk of collision with the ground in the cloud, there are probably many fewer potential conflicts than with the VFR flights bimbling around in the 200 ft just below the cloud.

We all like to think that collision avoidance in VMC is assured by see-and-avoid, and that collisions in VMC only happen to "bad pilots". In reality, collision avoidance in VMC is statistical, just as it is in IMC. Play the odds wisely.

[BEagle]

tmm - sorry, I misread the chart. Shobdon is 300 ft(ish) above sea level -it is the hills a couple of milesto the north which are 1000 ft amsl. But the hills between Sleap and Shobdon poke up to 1693 ft amsl.... I guess it was an 'interesting trip' from Sleap?

Personally I would have been very loath to leave Sleap at all, given those conditions. Had I done so, it would have been VFR and a very carefully plotted route. Aided, as IO540 will be pleased to learn, by carefully chosen GPS waypoints.

However, what I find very interesting is the fact that NATS seemingly put a price on safety concerning the feed of SSR information to Staverton. That is outrageous! Perhaps the issue should be raised in the response to the CAA's Mode S consultation?

You could have had a full Mode S installation and have been talking to Staverton shortly after having to make an unplanned climb into cloud. Yet Staverton couldn't have helped you because they couldn't afford the SSR feed? Is that really true?? If so, heads at the CAA, DfT, NATS or whoever should roll!

[mm_flynn]

Originally Posted by BEagle

However, what I find very interesting is the fact that NATS seemingly put a price on safety concerning the feed of SSR information to Staverton. That is outrageous! Perhaps the issue should be raised in the response to the CAA's Mode S consultation?
You could have had a full Mode S installation and have been talking to Staverton shortly after having to make an unplanned climb into cloud. Yet Staverton couldn't have helped you because they couldn't afford the SSR feed? Is that really true?? If so, heads at the CAA, DfT, NATS or whoever should roll!

I was in Coventry's tower 6 months ago and they also don't have SSR because of the cost of getting the data link (I was told), even though Birmingham is just a few miles away. I think they are planning to put their own SSR in (I can't believe this is cheaper ) and even better it is another ground station lighting up all of the transponders reenforcing the 'need' for Mode S.

[IO540]

I suspect that the only reason it isn't already banned is that NATS know full well that they haven't got the infrastructure to cope with providing full radar service outside CAS

I am sure that's true. In my native language, there is a saying which (translating very poorly into English as tends to be the case with word plays) goes something like: if you had fish up your ar5e then they wouldn't be in the pond.

Also I am not taking any "GPS baits", sorry Beagle

This whole business is run by anally retentive people. Technically there is no reason why every airfield operator should not be able to have a radar feed from NATS. It could be provided via a website. The amount of data to be transferred every few seconds is a few hundred bytes at most.

One problem is that NATS would charge for it, and most airfields won't pay for it (or for anything else for that matter, like a shovel and a wheelbarrow for filling potholes). The other problem is that the CAA would never allow "non qualified" people to see it.

In France, it appears common enough for airports without radar to have a radar feed appearing on a screen. Must be great for situational awareness.

[Sedbergh]

OK guys, enough of the nit picking. The consultation period ends very soon now. Please get your views (in whichever direction) to the CAA as soon as possible.

Personally I am against the proposal on the grounds of high initial and ongoing cost against nil benefit to most users of light flying machines.

However the CAA electronic response form is so slanted that almost any reply could be interpreted as "favourable". Therefore I recommend that an "against" opinion should be voiced in a letter, copied to your MP.