NigelOnDraft

Fuji.... Some thoughts / replies...

Good

The $64M question To begin to answer it, we could look at TCAS. Range, or rather Range + Rate of change in Range + Height Difference => Collision possibility assessment. As IO540- says above, a miss is OK - you do not need a large safety margin. I have had an RA, with 200+ people down the back, and the system demanded we "maintain V/S" (which was zero). We had the traffic visually (Biz Jet), and went very closely laterally to it, and 500' above it. It's not a lot, and a pilot might visually try and get more... but it was safe and all TCAS wanted

TCAS assesses range VERY accurately (since it can actively demand and time returns), and Height quite accurately (to whatever the 2 x Mode C device work to - in some GA applications, or even commcercial non-RVSM, I would not want to trust it within a few hundred feet?) Other systems assess range on signal strength (?) - fairly dubious to assess range accurately, and very for rate of closure (this is TCAS' strong point). IMHO TCAS and other ACAS systems are nowhere near up to assessing bearing accurately enough for either automatic, or visually judged vis screen, lateral avoidance - as the article above stated, it is too easy too reduce separation...

The other factor on "what you do" depends on judging the "target" is/might be doing. He might actually have seen you, and judged (visually) he is going to miss you, when you take some inappropriate avoiding action and reduce or even eliminate the separation. Again, a TCAS strong point is that where possible, avoiding action is co-ordinated - hence the compulsory need to follow it. Ditto - it might be taking avoiding action based on an ATCO, who has a more accurate picure...

You could run the argument that if you are concerned about your 6 o'c, you should always be weaving and looking behind you! What you do is again a difficult call... the traffic behind might have seen you and gets somewhat upset when you turn into his path.

I would probably do "nothing", because my training is (military) to trust my life on my lookout, and accept that without the latter, I am in trouble, and in my later life that you do NOT avoid on a TA, and await an RA - even though that trained for environment is not applicable to GA. In practice it is academic, I do not have such a system... and whilst following this debate is interesting, will await buying anything until a lot of these questions are resolved.

What you do is up to you, and see best at the time. The "problem" we are discussing is what we as a community advise you do, both in actions, and in equipment terms... and that carries the liability of ensuring the advice is truly fact based and risk free. TCAS has had a tough learning curve, and nobody wants to repeat that in a far less trained for / regulatory environment.

NoD

nav3

IO540 - You make a good point about the Avdyine Ryan TAS 600 which IS a good system. I had a C172SP G1000 until a few weeks ago (upgrading to C182T) and I have to say a couple of things related to this thread which are a bit peripheral, but very relevant.

Somebody said Mode S is a waste......well, it was badly handled which we all know. If it was one rule for all then fine ...that I do agree with.There are big benefits to be had but we all have to sing from the same hymn sheet.

The TAS600 I had fitted to the 172 because I wanted extra security. NOT replacement for the Mk 1 eyeball and it is amazing how many other targets are spotted by it. Most new Cessnas have already got the TIS system inbuilt but as EASA can't agree (par for the course) on a common frequency to transmit the data, it means that we again have to pay over here for something that is fitted to the aircraft and stops working as soon as you leave mainland USA.

The second point I wish to make is that many pilots (even within my own club) do not like talking to big airports. For some reason they will transit one of the busiest corridors (from the CT /Nuneaton up to Tatenhill) without speaking to anyone. Absolute madness. All it needs is education from the instructor to begin with and confidence and pre-planning. My instructor had a job keeping me OUT of Birminghams area. I enjoy talking to controllers and it is a two way thing. You inform them and they inform you. However, you would be amazed at the number of people transiting North right across the CT without a thought for anyone on approach to R/W 23. I have seen and heard it and it is obvious they are not on frequency or if they are, completely oblivious to what danger they could be causing. As it is Class G they feel it is theirs to do what they want with.

I am only a 150hr PPL but do take my flying and communication seriously and so should others. All discussions on this forum are very helpful as the threads often jog a memory or invoke a thought and if that one thought saves a life then well done PPruNe.

IO540

No approvals so not legally installable other than in a homebuilt/ML type, as far as I can see.

Some nice panel mounted versions

ShyTorque

Nav 3, sensible, balanced post, makes a change to see one on here.

Folks wandering about the skies with little appreciation of the big picture are a worry to us all, the instruction they aren't given must be one cause. Those who cross the approach path as you describe remind me of pedestrians who sometimes choose to walk across a busy dual carriageway from one side to the other and linger 'because they can'. Not illegal, but totally unsafe.

Robin400

We need a system that can be installed in a microlight to a 380.
Only then will everyone have a basic means of protection.
Transmitting one`s position and altitude for all to receive is the only way.
Mode "S"/ TCAS could then be left for the big boys toys.

Fuji Abound

I guess this encapsulates the point I was seeking to make. Your reaction was based on your ops manual and your training operating in a controlled enviroment using TCAS which provides a RA.

CAS typically used in GA does not provide an RA. Much of the time (given that most GA pilots spend most of their time outside CAS) the flight is neither at an asigned altitude or heading.

In short the pilot is "free" to do as he wishes.

To take the discussion a step further. With TA it is usually possible if you wish to establish vertical seperation of 1,000 feet and lateral seperation of 5 miles when the traffic first appears and well before any collision threat exists unless of course the system is vertically inaccurate by a least a 1,000 feet and inaccurate in distance by more than 5 miles and in bearing by more than 90 degrees. A miss is a miss but given the limitations of the system I am not sure on the desperate need to acquire the traffic given the very different constraints and speeds applicable in the enviroment we are discussing.

I agree, there may be an element of rewriting the manual but I would prefer to consider doing so rather than blind obedience to a procedure that has been inherited from a different enviroment.

I appreciate your comments about the way in which you would react. Your experience is interesting.

However I note that you have not responded to the specific example of two aircraft in open FIR in IMC. You will never acquire the traffic visually. The decision is simple. You avoid the traffic using the TAS before it remotely becomes a threat or you wait unitl you receive a traffic warning. I know whcih course I would prefer to follow.

mad_jock

And it has never been done by a VFR aircraft being told to hold on base to let a CAT aircraft go out bound on a pointless full procedure in CAVOK in class G to bobble up and set its TCAS off so it climbs so they can get in without waiting. Its happended to me a few times luckly my platform height out bound isn't the way oxford would teach it so we didn't have to react. It ain't the commercial pilots fault that ATC want to operate the airfield the way that they do. I have been MOR'd for canceling IFR in class G in CAVOK because they lost radar separation!!!!!!!!! It was the whole point of cancelling so we didn't have to do a 10 mile final and both of us could look out the sodding window.

Its one of these things thats going to happen if ATC continues to try and part the waves for CAT.

BTW Doncaster sounds ok at Dundee they use to star burst the VFR traffic as soon as the scot air had taken off out of City. Nothing could land once it had booked in with the scottish FIR.

NigelOnDraft

Surely any aircraft in IMC is receiving a minimum of RAS? And so the question is not relevant - you have to rely on ATC for separation? Please don't tell me people fly in IMC without such a service A RIS would for me, be risky, but anyway, the service provider should be giving the traffic information.

I do not tend to fly IMC outside CAS, and on the rare occasion I do, would always have a RAS - but that is my flying pattern. The thread to date I had treated as applying to VMC outside CAS..?

NoD

gpn01

When flying in OPEN FIR, presumably the Radar ADVISORY Service is such that they can only inform you about other traffic that the unit is either in contact with or which is painting a trace on their radar screen ? Therefore they can only give advice and not provide a completely controlled environment for any pilot who's IMC and requesting RAS ?

S-Works

I have a Zaon unit connected to my 496 that gives pretty good information and is compact.

I generally fly airways everywhere but I am based on a private strip so spend a lot of time transiting from CAS back and forth to the strip. On IMC days where I get a cloud break for a VFR landing I rarely see any returns. The clear VMC days it is a bloodbath and it is surprising the number of returns that I get and never eyeball.

Same problem as with TCAS etc. I need everyone to have a TXPDR and mode C so even with technology assisting me I still need to look out the window and be sharp on my lookout.

A question that perhaps should be debated is that are we letting our guards down with see and avoid when we are under ATC than for example when we are at a busy A/G airfield like Leicester or Popham etc. and expecting a bloodbath?

NigelOnDraft

But now the argument gets circular How can your "in cockpit" system show the target, but it is not on ATC's radar screen?

1 worrying answer - people rush out and buy FLARM, and not a Xpdr. Were we to get a drift to FLARM, we now end up with 2 incompatible ACAS systems. So (assuming the sytems perfect) Xpdr don't hit Xpdr, and FLARM don't hit FLARM, but FLARM and Xpdr hit each other?

It is I suppose an argument against FLARM - we have a number of ACAS "systems" based on Mode C, and any further systems should at least use that as a starting point?

NoD

Gertrude the Wombat

I was flying in IMC with RIS on Saturday. (The "information" was along the lines of "there's lots of aeroplanes in the sky, most without height information, you should be OK if you stick to your current heading".)

And I was lucky to get the RIS. Over much of East Anglia at the weekend there is no radar service available to GA in class G.

Robin400

How does that work? "Xpdr don't hit Xpdr" !!!!

I have mode S transponder but it does not give me any traffic info whatsoever. ATC and owners of SBS type equipment can see me, but other aircraft cannot (unless they are TCAS equipped).
That is why we need equipment that can be fitted to the smallest flying machine and affordable.

NigelOnDraft

I can understand that... what I cannot understand is anybody then choosing to fly in IMC in these circumstances But as I say, maybe just my attitude to risk - seems like driving down the M1 at 80mph in 50m viz fog

NoD

NigelOnDraft

When TCAS becomes universal, or an adaptation of PCAS or whatever it is, and all these other systems on the market Most of them are based on Mode C as a starting point e.g. TCAS will provide TAs and (uncoordinated) RAs on a Mode C. But FLARM is completely incompatible...

I am just making the point in the debate that Mode C is so well established, both between aircraft and with ATC, that future developments / training / rules might be best directed at these systems...

NoD

ShyTorque

Nigel, in the event that you discover there is no radar service available for part of your route in Class G, what would you do, turn back?

Unfortunately, we do not have the panacea of a full LARS coverage in UK, if anything it has reduced in recent years. Some of us certainly do have to "make our own arrangements" at times whilst flying in IMC in Class G. That is why I, for one, could never opt for FLARM instead of TCAS. I don't have the choice of cancelling a flight because of IMC conditions en route, at least, not if I wish to keep my job and not give it to someone else who would willingly take my place.

mm_flynn

In my experience, there are a number of parts of the UK where, depending on time and day, a radar service outside controlled airspace is only available on an adhoc basis. In the South there are also a number of places where a RAS is impractical as there isn't enough space to get 5 miles and/or 1000 feet against any other OCAS traffic.

The choice is either live with the risk (after all on an IMC day there are a lot less aircraft - and statistically mid-airs only happen in good VMC conditions) or don't fly on IMC days other than on airways flight plans from airports with radar approach control .

NigelOnDraft

ShyTorque...

Your post is exploring an area outside my experience... so you know the risk(s), and whether they are worth it? Not a problem to me, since I would not meet you coming the other way, and as other posters note, nor many others, which in turn reduces your risk...

Out of interest, does your job involve pax on this basis? Or just qualified crew who know the implications?

NoD

madlandrover

Going off topic for 2 seconds: I haven't been into Dundee for over a year but they seem to have tightened up a bit over the last few years (other than asking my boss to orbit downwind after he called a Mayday over the river!) - a number of times the Do328 was no2 to me rather than the other way round, quite refreshing compared to some other northern airports. I wonder if it's changed with HIAL?

Getting back on topic: there's a lot to be said for approaches in CAS - other than putting in some orbits on an IRT last year, I haven't been held up, delayed, or had any problems over the last 14 months operating in/around CAS.

Fuji Abound

Isnt a further problem than even with a LARS not all targets will be seen on primary. As I understand it gliders do not paint well, as is also the case for some composite ultra lights as originally suggested in this thread.

I appreciate they should not be in IMC but you may be descending through an undercast and there is always the risk the first thing you will meet is a glider very close to the base which is not transponding and not being painted on radar.

Of course there has never been a mid air between two aircraft outside CAS in IMC in the UK so the record is in favour of not meeting another aircraft.

I can think of a number of commercial operators that are public transport that operate outside of CAS and do not carry any form of TCAS. For example there are regular commercial flights from Shoreham to the continent who at best might get a service from Farnborough for a few minutes but are outside their cover over the channel and not within Lilles cover.