Mode S ... who benefits .. ?

[PH-UKU]

Certainly not the VFR pilot struggling to meet current high bills and over legislation. :*

I currently operate out of Class D. I don't have a transponder. It has never been a problem for ATC - who are fantastically helpful by the way. I am operating VFR in Class D for perhaps 5 minutes until I get out into the open FIR where I then 'see and avoid' and don't speak to any ATC provider - cos there is no radar or radio cover in the mountains.

I think we (or rather the desk pushers who make the rules) have a real tendency in the UK to try to over control VFR traffic, and this (Mode S) will just make it much much worse. Perhaps a sad reflection of the fact that so few ATCOs (or pen pushers) actually fly or understand that there is a huge amount of legitimate aviation outside of the sacred lo-costs ? Witness the large amount of mixed GA successfully integrated with big jets all over the USA imagine that in the UK ...

But back to Mode S ..... I've seen the cluttered radar displays all around the UK, particularly in local areas and mil training areas. Look at the displays at Scottish Centre - tiny 20 inch screens for 150-250 mile sectors - every SSR label is about 15 (yes 15) miles across.

Imagine if EVERY flying machine now has to squawk. Every glider, microlight, balloon or binbag. You are going to be faced with one glowing cluttered screen. And before someone says that you can height filter out ... not if you are operating below FL100 or outside Controlled Airspace as standard.

But the real issue is that I am expected to pay for someone elses supposed commercial gain. If it costs me or my company a (compulsory) £3000-£3500 to buy fit and test for each aircraft, who will compensate me for my loss ? What benefit is there to me ? I really would like to know. Rachael Reid (Corporate Comms) of NATS at one meeting said NATS might pay for fitting Mode S ... I'll believe it when I see it.

If someone forces me out of my house to build a new road (for other peoples benefit), I would be compensated, and rightly so.

Now, perhaps the one advantage in mode S I can see would be if the fast pointy jets were also fitted with compulsory ACAS/TCAS to see other traffic. But they won't be. If you look at the Big Bumper Book of Airmisses, you will see fast.pointys feature very very highly - rough check about 40%. That tells me there IS a problem with military jets seeing and avoiding other users.

Any views out there that are worth sending on to the CAA consultation ?

[Sedbergh]

I'm sure you're right, but these days Auntie Blair & Uncle EU virtually demand that you call in a "professional" electrician to change a light bulb & a "Corgi" gas fitter to light your stove.

So don't expect any sympathy for "rich" pilots:{

[Fournicator]

While mil fast-jets may feature highly in REPORTED airprox, a little bit of closer investigation is quite interesting. Generally, when you look at the results of the board's discussion of such incidents, you'll find that they concluded that NO danger of collision existed, becuase the military pilot had been watching the other ac for a while, and was ensuring separation. The airprox is generally filed after a late spot by the other pilot freaks them out a bit. Sweeping generalisations, yes, and there are exceptions, but if you're going to use statistics please actually look into the detail before you do so.

Incidentally - couple of reasons which contribute (IMHO) to mil ac often getting the spot first:
1. Lookout is drummed into mil operators as an absolutely vital skill right from the outset of training, and is hammered home much more vigourously than in GA training.
2. As the mil ac will generally be flying lower, he/she has the advantage of the other ac involved being skylined, making them far easier to see than when viewed against a background of ...... errrrr ......... ground.

Donning tin hat for the inevitable barrage of angry responses.

[chrisN]

F, is there a possible third reason too - potential conflict between fast jet and GA/glider/microlite etc. is mostly in the former's 10 o'clock to 2 o'clock because of relative speeds, so more often easier for the fj pilot to see from a distance. Anything travelling slower can have conflict coming from any direction, about half (or more) out of sight.


Chris N.

[blue up]

Recently talked to one of our drivers who came close enough to 2 F15s to hear the roar of the engines as they passed. 757 is bigger than your average Mig but they still managed to nearly scrape paint.
Question.
Do Mil pilots have radar/IFF ON whilst transiting UK airspace? Bit of a giveaway if you are playing wargames with each other. What is the RAF/USAF policy?

If a 30 watt Mode-S has a theoretical 50 mile range (say 25 real miles), then how much MORE warning of proximity would it actually give over Mk1 eyeball? Not full knowing how Mode-S works, I'm assuming that units "talk" to each other, rather than via a central ground station.

Is a 30 watt Mode-S equipped Cessna 150 noticeably safer flying round or is it likely toreduce safety by giving a false sense of security. Like the old suggestion to remove airbags and replace them with metal spikes in order to get cars to leave more space between them.

[IO540]

That tells me there IS a problem with military jets seeing and avoiding other users.

For all the stuff said and written on this, visual avoidance doesn't really work. This is because - assuming straight line 3D trajectories - if a target is on a genuine collission course, it will be a completely stationary spot in the sky, and unless you are lucky you will see nothing. Especially if (like most) it is painted white.

Most of the time, when you spot a plane which looks like it is awfully close, the very fact that you spotted it means it wasn't.

I realise the above is going to really get a lot of people going, but it is a geometric fact. See and Avoid doesn't work anywhere near as well as per the advertising. People think they keep a great look-out but what really keeps them out of trouble is the big sky. Anyway this is self evident when flying under an RIS or with TCAS; far more targets than are ever spotted, even with four pairs of eyes looking in the approximate direction.

The bit where looking out works well is with maneuvering targets e.g. gliders and aeros.

I don't know the politics pushing Mode S but remember this is a Europe-wide (and to a lesser extent worldwide) issue.

The Americans have a much more powerful GA lobby and they have a) not made Mode S mandatory and b) have provided traffic info up the Mode S backchannel as a carrot to get people to install it.

My view on the UK politics is that if Mode C had been made mandatory many years ago, along the lines of the Mode C veils in the USA, the outcry would have died down by now and we would not have the present problems where a lot of low-end VFR traffic may have to install it. But this is the way GA works here: you dig your heels in over every issue like it was the end of the world, and then when you lose it is a major issue forced through from higher up and with repercussions which have not been properly thought out.

I guess the final straw that brought Mode S was the several hundred major airspace busts every year. They could have mandated Mode C but Mode S is the logical technical choice at this point. However, in the meantime, pilot training continues as before.....

For anybody flying outside the UK, and for anybody flying IFR, it's no use blaming anybody over here. May as well vote for leaving the EU membership :)

[chrisN]

Gliders using FLARM for glider/glider collision warning - effective range about 3 km and glider speeds typically up to 100 knots - have been found to be almost totally effective at preventing collisions. I should imagine that 25-50 mile range for speeds up to 200-300 knots would be at least equally effective.

(FLARM is a £300 device invented by and for glider pilots in the Alps, now extended to competitions in Australia and some places elsewhere. A sort of ADSB-light, I have seen several postings by glider pilots telling of it warning of another glider they had not spotted in time to react. If all GA and gliders had it, the GA/glider collisions would be solved far more cheaply than Mode S. If TCAS/ACAS and military equivalents had a FLARM receiver as well as Mode S, the heavy/fast metal would also have protection. CAA know about it but won't go that route - they are wedded to Mode S and refuse to listen to sense, AIUI.)

Chris N.
==========================

[Rod1]

IO540 is quite right; the mode s idea is Europe wide. I have just returned from a week touring France and can report that the DGAC have allowed the French ULM’s (micros to us) a blanket exemption. This is 8000 aircraft, including 3-axis capable of 135kn!

The PFA response to the CAA document contains some very strong arguments for PFA and BMAA type aircraft to be excepted, and the French action will obviously assist this cause.

Rod1

[jabberwok]

Not full knowing how Mode-S works, I'm assuming that units "talk" to each other, rather than via a central ground station.

Yes they do - so it's line of sight rules. So for two aircraft at 3000ft the theoretical maximum is around 120nm.

I've been looking at the interesting threads on a Mode S receiver web site. I'm not sure if Prune allows links to commercial sites so I won't push my luck. One picture shows the reception a user in the IoM is getting from an aerial on his roof -
http://www.homepages.mcb.net/bones/Kinetic/SBS_SS2.gif

I know the visible targets are ADSB equipped aircraft only but Mode S equipped aircraft are also picked up by this unit. Although the majority of the aircraft shown appear to be high level a close look at the picture shows a couple of aircraft approaching Dublin down at 4000-5000ft.

The moral of the story seems to be not to buy an ADSB transponder and have one of these boxes in your house otherwise your dear other half will know EXACTLY were you are (within line of sight that is..). :}

[IO540]

Yes they do - so it's line of sight rules

Not quite.

It's line of sight for TCAS purposes - there the TCAS interrogator (usually aboard an airliner, but GA versions can be had for about £15k) interrogates Mode C or Mode S transponders. This AFAIK is the only time when two airborne systems talk to each other.

Otherwise, the transponder (Mode C or Mode S) is interrogated by ground radar only. This is line of sight but can go slightly past the visible horizon, and you can easily have a situation where the transponder return is all you have; the primary return is long lost.

That picture above presumably comes from one of those PC-attached boxes which picks up the Mode S returns, but those transponders will not be making the returns unless triggered by ground radar (or perhaps TCAS as well; I don't know if a response to a TCAS signal returns the whole lot).

The position information is visible only for targets which return it in their Mode S data; typically this will be only airliners. A standard Elementary Mode S return is just a world-unique 24-bit number which can be used to look up the aircraft callsign. Actually there have been cases where duplicates have been encountered... I know somebody who saw his very own plane on his box and checked and it was parked at the airfield. Obviously the system isn't foolproof.

The main difference between Mode C and Mode S is that with S the ground radar can tell the receiver whether to respond or not; with C it always responds.

[jabberwok]

Otherwise, the transponder (Mode C or Mode S) is interrogated by ground radar only. This is line of sight but can go slightly past the visible horizon, and you can easily have a situation where the transponder return is all you have; the primary return is long lost.

OK. So for operational purposes could we assume the range difference between Mode S and C is minimal? (Assuming both are picked up by the same radar head)

[Shaggy Sheep Driver]

Bottom line is, Mode S adds no value for the VFR bimbler, yet he/she will be expected to pay for the purchase, installation, and ongoing maintenance of such a device.

By any measure, such an imposition is outrageous. :mad:

[Lucy Lastic]

.... and this is to benefit the lo-cost airlines by letting them take shortcuts through Class G and the MoD so that they can use UAVs all over the country.

Australia is considering paying for the kitting out of aircraft with Mode S, the gains are so great for them. Typical UK, we are prepared to let big businesses increase their profits at the expense of the little guy.

[IO540]

So for operational purposes could we assume the range difference between Mode S and C is minimal?

Correct.

What happens however is that if you have multiple Mode C targets on approximately the same azimuth (bearing) from the radar, their returns will be jumbled, because they all respond together, and all respond on the same frequency. With Mode S, once a sweep or two have been done to compile a list of nearby targets, you can then interrogate them selectively. (I don't know the protocol but guess it would be similar to a periodic scan on an ethernet network to find out who is connected.) This is one advantage of Mode S; the other is that the Enhanced Mode S version (basically applicable only to > 250kt planes) will return stuff like autopilot settings which helps ATC.

One can always argue about this kind of stuff, but one reasonably non-hysterical way to look at it is to regard Mode S as GA's half of a deal for continued access to the airspace.

The airlines call the tune; GA is practically irrelevant in Europe. One could shut down all GA activity in Europe and nobody outside GA would notice; those living near airfields would love it because their properties would go up in value :yuk:

[robin]

So for operational purposes could we assume the range difference between Mode S and C is minimal?
One can always argue about this kind of stuff, but one reasonably non-hysterical way to look at it is to regard Mode S as GA's half of a deal for continued access to the airspace. :

That is certainly what the CAA is saying, but there is no evidence for that. ATCOs will continue to give or withhold permission for flight in Class D based on controller workload. Although strangely, the proposal does not insist on the carriage of radio.

What is more worrying is the attempt by the CAA to make UK airspace a 'known environment'. GA is already excluded from vast areas of airspace, and we won't get that back. We are likely to be excluded from other areas too, and Mode S is not going to help there.

[I]The airlines call the tune; GA is practically irrelevant in Europe. One could shut down all GA activity in Europe and nobody outside GA would notice; those living near airfields would love it because their properties would go up in value :yuk:

I agree that the airlines are calling the shots, and certainly some local residents will be cheering - that is until they get an IKEA store or an estate of affordable housing going up on the ex-airfield

[S-Works]

What airspace as GA users are we denied access to? The only place I can really think of is the Heathrow ATZ for a pretty good reason.

There is nowhere that I have encountered that I can not fly through. Is the discussion around airpspace down to pilot qualifications? I want access to clear sky above which was in the airways in my G-Reg, as a "Vanilla" PPL I could not do it so I went out and got a JAA IR. Now I can go where I want.


I have a Mode S transponder a nice shiny new Garmin linked to my GNS430 etc. It is relaible and modern and goes in and out of STBY automatically. It would be nice to have traffic information USA style but as IO540 says the cost of a transponder is the cost of living in the grownups world.

A lot of these discussios revolve around the fact that people dont want to move in to the 21st Century, upgrade avionics and qualifications. But sadly we are now a long way from the early part of last century where the skies were free and you could do as you want. Owning a vintage aircraft may help to cling onto this romantic notion but it does not change the facts. Commercial aviation will get priority as the labour voting majority are the same people who like their cheap two weeks on the Costa Del Sol. Keep the lemmings happy and you keep the votes on your side.......

[robin]

I want access to clear sky above which was in the airways in my G-Reg, as a "Vanilla" PPL I could not do it so I went out and got a JAA IR. Now I can go where I want.
I have a Mode S transponder a nice shiny new Garmin linked to my GNS430 etc. It is relaible and modern and goes in and out of STBY automatically. It would be nice to have traffic information USA style but as IO540 says the cost of a transponder is the cost of living in the grownups world.....

I think that says it all really, when the GA fraternity can't even agree amongst itself.

An IR is something that is acknowledged to be a good thing, but horribly expensive to gain and maintain - most of us wouldn't even think of going down that route, flying as we do from small airstrips without all the somethings.

As for buying a GNS430 etc, that costs more than I spend on maintenance, hangarage and insurance for the year. I would doubt my panel could accommodate it, and my power supply (a portable battery, for my radio and Garmin 55 GPS) certainly wouldn't.

I envy you your ability to fund that sort of flying, but I have had lots of fun flying in the open FIR not bothering ATC and dropping in at various fly-ins. I like a late evening bimble after work and given that the local ATC is off duty, I don't feel the need to speak to them.

This is the sort of flying that the majority of GA pilots do, not IR flight. It might well be considered grown up to fly above the weather in an expensively equipped aerial carriage, but some of us (probably most of us) would never be able to afford to do that, even if we wanted to.

Mode S, in my view, is not the way forward for the vast majority of pilots (gliders, PFA, microlighters) and we, in GA, should accept that there is no clear black and white solution for this and be a little more considerate of other's firmly held views.

[Fournicator]

Sorry, bit away from where the thread's now gone to.

Chris:
Fair point, but as we're also busy looking for other mil FJ ac, especially 'bounce' ac, we're busy looking in as wide an arc as possible, not just the 10-2 arc. You're right though, however hard one tries, lookout will always be better in the forward quadrant.

[IO540]

I think that says it all really, when the GA fraternity can't even agree amongst itself

The problem, robin, is what should we agree on?

Should we dig in, UK AOPA - style, and fight every issue to the death of the last man? That certainly won't work, and things are already at the stage where the powers to be just snigger when certain well known names are mentioned.

Or should we accept that some things are not worth fighting for, on the basis that we will get something else for it in the long run?

The UK has a substantial low level flying community, operating from farm strips etc. They have had an essentially unchanged environment (so long as they keep to Class G) since aviation was invented before WW1. I can understand they don't want any new technology and probably most of them demand the right to fly non-radio also. I have no problem with that, but unfortunately GA in the UK isn't categorised into

a) farm strip flyers who never go outside Class G, and

b) everybody else

:)

The privileges of a PPL are right across the board. Maybe this is wrong but that's what we have. And any pilot can bust airspace, etc.

And I am not even talking about the GA IFR scene which Bose X referred to.

[mm_flynn]

I recently attended a CAA/ RIN briefing on Mode-S which extolled a number of benefits, however, the benefits to GA were basically:

1 - Reduced chance of being mowed down by a CAT (so far a non-existent event in the UK - although there are airproxes - but on a downward trend)

2 - Reduced chance of being mowed down by the mil - but not applicable to trainers, current fighters (other than the Tucano) and helicopters due to the lack of plans to fit ACAS.

3 - Not being 'segregated' from CAT in different airspaces - although to a certain extent this already happens with the limited staffing NATS seems to have to deal with VFR traffic in class D.

These benefits are achievable with any transponder technology, and all of the technologies have the same issues in aircraft without electrical generators - which are likely to have a technical exemption until 'practical' technology is available.

The reason for Mode S vs. Mode C (cheap second hand, given all of the IFR guys need to scrap their Mode C) is alleged saturation of the SSR frequency with the planed increase in CAT traffic and the desired increase in transponder usage. Why this isn't a problem that needs to be resolved in the US with the higher traffic density and the Mode C veils is a question I don't understand.


There was also a view expressed from the audience that the 'real' reason was to enable high levels of military, police, government us of UAVs for detecting violations of parking, traffic, building, hose pipe, etc rules and regulations - and another view, that only ADS-B provides sufficient data to safely use UAVs in the open FIR.

In summary, there appears to be no real benefit of Mode S for anyone - other than the ATC features in Mode S enhanced and the reduction in SSR frequency saturation that the 'Selective' part of Mode S provides.

A member of the Airprox board had the opinion that the usage of any tranponder technology was of beneift in reducing airproxes, which I would tend to agree with. Although, the number of glidders, microlights, etc without any viable means of powering a transponder will mean see and avoid is needed for years to come.

[robin]

I think that says it all really, when the GA fraternity can't even agree amongst itself



The UK has a substantial low level flying community, operating from farm strips etc. They have had an essentially unchanged environment (so long as they keep to Class G) since aviation was invented before WW1. I can understand they don't want any new technology and probably most of them demand the right to fly non-radio also. I have no problem with that...


But the issue for the strip flyers is not just that they don't want it, it's that it is unaffordable or very expensive and gives them very little in return. If you fly, say, a Jodel D9 with limited panel space and no electrics, except for a small battery pack, do you choose to disable the radio and GPS to power the Mode S? If you do, how will you know there is something nasty coming towards you?

Add to that the fact that, say, in a glider, microlight or rag and tube aircraft there are serious risks to health through radiological damage, so much so that in France and other EU countries it is considered no appropriate to use the new kit

Finally, if you fly a small Jodel, costing around £10k or less, a £4.5k piece of kit is a very expensive item. There are no signs that the cost will be brought low enough to equip the recreational fleet at an affordable level.

The CAA is moving ahead of all other European countries by a wide margin - no-one else intends to impose this to their entire airspace, as the CAA proposes. And they also intend to offer an alternative that may not be acceptable elsewhere.

Bear all that in mind, and we have a choice - we either mandate Mode S for everyone (and radio and TCAS) and force out the low end of recreational and GA flyer, or we work to ensure that the CAA start to listen to their aircraft owners - as other EASA countries are doing - and come up with a workable alternative

Fortunately the BGA and PFA have moved ahead of AOPA UK, (who seem to want to work on their own) and have come up with a reasoned response to the CAA's paper

[IO540]

Good points but also some hysteria.

The radiological damage is bunk. The average emission power is miniscule; no more than a 400mW (max) mobile phone.

There is no suggestion of mandating TCAS for GA. The commercial transports have to have it, which is reasonable.

I suppose the problem with the Jodel example is that it could ask for a Class D transit. You could suggest the obvious olive branch (limiting all these types to Class G, with no exceptions whatsoever) but I don't think this would go down too well with most of the pilots.

The other thing, again looking at this from the CAA point of view, is that the Jodel is just as capable of inadvertently ending up overhead Heathrow as a £250k IFR space wagon whose autopilot is tracking the GPS. Of course I would say it is far more likely to do so, but I am sure you would disagree :) But the fact is that great many of the "low end" types do infringe, just as the standard spamcans do. I was on the phone to a Class A unit once; they said about 20 microlights went straight through their space that morning, completely oblivious, after some convention.

Personally I am not bothered either way. What annoys me very much is people who probably have (or easily could have) Mode C and don't use it, very likely deliberately, which makes a radar service basically worthless. I don't mind nontransponding contacts being below say 1000ft AGL; above that I think they should give a bit of consideration to other airspace users.

[PH-UKU]

bose-x
There is nowhere that I have encountered that I can not fly through.

How about the 4000 square miles of the Highlands Restricted Area - north and west of Loch Ness to Skye, Cape Wrath and John O'Groats? Some of the most stunningly beautiful landscape in the UK - perfect for flying visitors to tour Scotland and perfect lochs for float-flying ...... but generally closed to civil traffic 3pm-11pm Monday to Thursday.

Interested to know how many movements per year per square mile .... bloody waste of good airspace.

[Rod1]

“The radiological damage is bunk. The average emission power is miniscule; no more than a 400mW (max) mobile phone.”

The PFA have some extremely compelling science which has been put together by some very highly respected boffins which says you are wrong!

“But the fact is that great many of the "low end" types do infringe, just as the standard spamcans do.”

The analysis which is ongoing comparing infringements by PFA types and C of A types is incomplete, but the provisional results seem to show that the PFA aircraft are, in % terms, much less likely to infringe.

“What annoys me very much is people who probably have (or easily could have) Mode C and don't use it,”

That would be me then! I put a second hand mode a transponder in my plastic fantastic instead of a brand new Garmin mode C because of the mode s proposals and the likelihood I would have had to scrap the Garmin. I know of many other builders who have gone the same way.

Rod1

[S-Works]

There was about £500 quid difference between a Garmin Mode C and a Garmin S when I just had mine done. Where is the argument for people who build (and some of these kits are lavish) a plane then put a cheapo transponder in?

Simple answer for those who dont want to or cant put in a Transponder is restrict them to Open FIR only with a buffer zone from CAS? No transits etc.

[Rod1]

Bose

It took me 3 years from purchasing my avionics to getting the aircraft flying. My second hand transponder cost £500 and a mode s at the time was £4000. The cost difference now is still over £1000 so it is not hard to see why the strategy is so popular.

Rod1

[IO540]

The point re Mode C is that it is actually useful, to ATC, to anybody getting a radar service from ATC, and to anybody flying with TCAS on board.

You are also probably more likely to get a transit with it in some places, even if UK ATC staff are bound to deny this if asked openly. That's even before we get onto the "abroad" subject.

Whereas a Mode A transponder does precisely nothing more than duplicating the primary return, with an optional squawk. Since UK ATC are not (AFAIK) allowed to offer any kind of radar service unless they see the primary return (regardless of any secondary one), a Mode A transponder may meet some legal requirements but despite returning a squawk it about as much value as, to use my favourite phrase, a chocolate teapot.

I sold my old Mode C on Ebay for about US$1300. It was 3 years old, in perfect condition; a KT76C with push button selection, perfect sunlight readability, flight level display, etc. I don't understand anybody fitting a Mode A when they could get one of these.

[robin]

There is no suggestion of mandating TCAS for GA. The commercial transports have to have it, which is reasonable..

My point is that CAA propose to mandate a transponder so that we can be 'sensed and avoided'. However, as you say, there is no proposal to mandate TCAS (or indeed radio), so the benefit accrues to the commercial and military fleet - as is acknowledged in the RIA.

The ATC aspect appears to be a secondary issue - on the one hand they say they can predict a potential collision or incursion using the new equipment, but may have no means of informing the 2 aircraft, as they can still be non-radio.

The required lo-cost, lo-powered Mode S does not yet exist, and may be of little use for ATC purposes, but only for TCAS/UAVs


I suppose the problem with the Jodel example is that it could ask for a Class D transit. You could suggest the obvious olive branch (limiting all these types to Class G, with no exceptions whatsoever) but I don't think this would go down too well with most of the pilots.


I note that AOPA are asking their members to report the occasions they have had transits denied. This is a growing problem and Mode S will not help, as permission is controller workload dependent

Personally I am not bothered either way. What annoys me very much is people who probably have (or easily could have) Mode C and don't use it, very likely deliberately, which makes a radar service basically worthless. I don't mind nontransponding contacts being below say 1000ft AGL; above that I think they should give a bit of consideration to other airspace users.


I think Rule 5 might be a slight problem there. But it is not a good idea for us GA pilots flying microlights, sailplanes, Jodels or airways-equipped TB20s to denigrate each others choices.

Sure, if you fly in CAS then Mode S is certainly worthwhile. But the costs of Mode S are such that it has the capability of removing a huge part of the pilot population at a stroke on the grounds of affordability, all so the MoD can save money and Ryanair can make more profit

[IO540]

there is no proposal to mandate TCAS (or indeed radio), so the benefit accrues to the commercial and military fleet .

It also accrues to anybody who has TCAS or any sort of traffic warning capability. Simple (IMV near useless) boxes can be had for £500 but the other day I saw one which gives azimuth too for about £1000 - this is hugely significant as the principal point of the £15000+ systems is azimuth info, without which you don't know which way to turn and the only avoidance option is a climb/descent, while hoping that the other man's transponder encoder isn't completely knackered.

The ATC aspect appears to be a secondary issue - on the one hand they say they can predict a potential collision or incursion using the new equipment, but may have no means of informing the 2 aircraft, as they can still be non-radio.

Well, if you don't have a radio then you have denied yourself that pretty basic capability pretty effectively, and IMV have nobody else to blame for not being able to offer you a service.

I note that AOPA are asking their members to report the occasions they have had transits denied. This is a growing problem and Mode S will not help, as permission is controller workload dependent

I know this has been discussed here before but I think there are other factors too apart from workload. I would be suprised if ATCOs suddenly stopped being human when they come to work.

Sure, if you fly in CAS then Mode S is certainly worthwhile. But the costs of Mode S are such that it has the capability of removing a huge part of the pilot population at a stroke on the grounds of affordability, all so the MoD can save money and Ryanair can make more profit

I don't see how Ryanair will make more profit by abolishing GA. Once airborne, their profits depend on the route flown (fuel usage) and they will be either in CAS nearly all the time, or so high that non-turbine GA is irrelevant.

I have no wish to "denigrate" any choices, but if one bunch of pilots choose to fly without Mode C or Mode S, they are making a radar service largely useless for everybody else, and the obvious conclusion there which would protect everybody's civil liberties to is close down the LARS system. Now, that really would save a few million!

[Rod1]

a chocolate teapot

I have had no problem getting clearances so far with mode a, but no transponder would be a problem. If I have an a/c problem, the ability to squark 7700 makes the cost of my unit well worth it and whilst I like chocolate, I would not swap it! If, as seems increasingly likely given the French exemption, the PFA/BMAA machines are exempted then I will re-evaluate but if I had to make the same decision again I would do the same as I have so far. I may add mode c to my existing unit if mode s goes away.

At least I had the forethought to put the transponder aerial under the passenger seat!

Rod1

[PPRuNe Radar]

IO540

Since UK ATC are not (AFAIK) allowed to offer any kind of radar service unless they see the primary return (regardless of any secondary one)

Not 100% correct. ATC units can get permission from the CAA to provide radar services using SSR only. The conditions under which they may do so will then appear in the unit Manual of Air Traffic Services. For example, some Scottish Area sectors have access to radar sites which are SSR only, hence they can limit the service when using those radars (not that they have any choice in the matter ;) ). Or units can use SSR only if the primary radar has excessive clutter either due to permanent echoes or weather conditions.

Simple (IMV near useless) boxes can be had for £500 but the other day I saw one which gives azimuth too for about £1000 - this is hugely significant as the principal point of the £15000+ systems is azimuth info, without which you don't know which way to turn and the only avoidance option is a climb/descent, while hoping that the other man's transponder encoder isn't completely knackered.

All current ACAS kit, even the most expensive and advanced you could buy, should not be used to assess avoidance in the azimuthal plane. The bearing accuracy can be in error by up to 30 degrees so you could turn the wrong way. Pilots are specifically taught (and reminded regularly) not to take avoiding action using their ACAS kit except in the the vertical plane.

ACAS III equipment will provide both vertical and horizontal capability but the standards have not yet been set by ICAO and development of such equipment is stalled until the standards have been set.


I know we have missed the boat in having Mode C veils around major airfields or controlled airspace volumes (such as those in place in the USA), but perhaps there is some leeway to go for Mode S veils instead, and mandate carraige everywhere else above a certain level (5000' would be my opener). That would provide protection for the important commercial areas, whilst still giving some freedom (depending on your location) for low level operators.

[PH-UKU]

IO540 wrote - Well, if you don't have a radio then you have denied yourself that pretty basic capability pretty effectively, and IMV have nobody else to blame for not being able to offer you a service.


Rather simplistic view I think.

What percentage of aircraft do you think actually speak to ATC when they are transitting ? I would suggest that a very large percentage don't bother - a) because they are VFR and outside CAS and B) because often the frequencies are so busy that it can be a pointless call.... unless you then get radar indentified and receive a RIS.

A good case in point was the 78 aircraft that visited Strathallan for a fly-in 5 weeks ago. If 78 aircraft called me on 124.5 looking for a RIS, or called the FIR (no radar) on 119.87 ...what kind of service do you think they would get ? What do you think the radar screen around Strathallan/Perth will look like with 78 Mode S returns ? :ugh: with a 200 mile sector, 19 inch monitors and every label being 20 miles across ....

I would further suggest that if everyone (microlights, SLA, gliders, SEPs etc...) started to call up ATC to make use of this "basic capability" the system would collapse due to RT workload.

And no-one has yet answered what benefit it is to those of us operating amongst the mountains below radio and radar cover.

I say again - ATC will be in danger of making a rod for its own back if it demands Mode S from everyone. :=

PPrune Radar seems a sensible chap .. I like the idea of exempting it below say 6000 feet (gives us a 1000 feet over the mountain tops ;) )

And anyway, even if I fit Mode S, who is going to know if I switch it on or off ? Will I be banned from operating VFR outside CAS if it doesn't work ? Who is going to police this .. speed camera UAVs or a bunch of redundant fighter controllers ? God help us ....

[PPRuNe Radar]

I like the idea of exempting it below say 6000 feet (gives us a 1000 feet over the mountain tops

Let's haggle .... how about 5406' AMSL ?? :)

[robin]

I say again - ATC will be in danger of making a rod for its own back if it demands Mode S from everyone. :=
.

I don't think ATC actually want this, and it certainly isn't the driver as far as CAA is concerned. What will happen, though, if Mode S were to be mandated outside CAS is that we would all start insisting on a Radar Service. Given recent experience on a trip to Cambridge and back we are not going to get it.

I was with a friend who was Mode C equipped, but I was told to stand-by by 3 separate LARS units for so long, I was out of their areas before they might have got back to me.

No, this is for 'efficient use of airspace' and designed to let Sleasyjet Chavair 757's extend into Class G - and s*d GA.

[IO540]

There is a lot of conflicting factors in UK GA.

PPL students are taught to call up everybody under the sun. This increases the cockpit workload drastically. Yet it's obvious that if everybody flying VFR called up London Info (or Goodwood Radio, etc etc) as they have been taught, the whole system would collapse. The A/G radio operators would go bonkers. I am sure ATC don't want to have PPLs calling them up for a pointless "17 aircraft known in your area" FIS, professional though they are about it.

Except for S&R purposes, there is no point that I can see in calling up anybody unless one can get a radar service. But can one get it? The LARS coverage map of the UK is ever so impressive but in reality one cannot get a radar service much of the time, due to controller workload usually.

I suppose, Robin, one tradeoff which you can debate is whether you want more Class D, or fit Mode S. I have an IR so could just be selfish and say Sod all these VFR bimblers while I sit at FL140, on autopilot and watching the view and the GPS, with CAS, TRAs and national boundaries falling into irrelevance, and my only worry being icing (if in IMC), embedded nasties, whether I should ask for a descent to FL100 to save the oxygen in the bottle, and which of the 24 STARs for the destination/alternate I need to have handy. But actually I enjoy little local flights along the coast, or just plain drilling of holes in/around some clouds, and I think that Class G is worth looking after.

Taking it further, abroad, I have a 2 week holiday coming up, with 4-5 destinations and 4-6 hour legs. We will go VFR when we can, for the better low level view, with IFR being available if needed to get a move-on.

The quid pro quo for being able to do this will be the carriage of a transponder.

Unfortunately, "quid pro quo" is an alien concept to a large bit of the UK GA scene. I don't blame them; I would do the same in their position. With all the challenges facing GA as a whole (airfields chucking out GA, closing etc) farm strip flying is as secure a pastime as anything can be.

The damned things should have been made mandatory (Mode C) years ago, above a few thousand feet and for everything that's powered and can have one fitted. Plus Mode C veils. What we have now is a mess.

[robin]

I suppose, Robin, one tradeoff which you can debate is whether you want more Class D, or fit Mode S.

I think there are more options than that

What we have now is a mess.

We can agree there!!!!:ok:

[DFC]

“What annoys me very much is people who probably have (or easily could have) Mode C and don't use it,”
That would be me then! I put a second hand mode a transponder in my plastic fantastic instead of a brand new Garmin mode C because of the mode s proposals and the likelihood I would have had to scrap the Garmin. I know of many other builders who have gone the same way.
Rod1

I think you may find that the transponder is perfectly capable of trnasmitting mode C. It probably even has an ALT or C position on the switch.

The reason why you do not transmitt mode C is that you have not instaled a blind altimeter and the appropriate cable to the transponder. Not an expensive item at all........even for a new one and you will need it for when you install the mode S.

Regards,

DFC

[Rod1]

DFC

You are 100% correct on the mode C but several of the mode s units have it built in. Fitting an encoder would cost about £150 ish all in but it is three weekends work by the time I have taken the tank out, wired it all in and then put it back together. If I go mode s I would have to rip it all out again, so for now she stays a only.

Rod1