Mode S: do we need it in GA?
 

I fly a group owned touring plane, and we are having a discussion (about money) and whether we really need to upgrade a perfectly serviceable Mode C to a Mode S.

One or two members have IMC rating, in fact one is progressing to PPL-IR.
The rest of us are VMC only, but like to know where we are.

Having tried to understand the rationale, I am still struggling to see why, or where, we would need Mode S. Apart from local flights in SW England/Wales, the typical routes include Lancashire, Ireland, Channel Islands, France and the near Continent. The furthest we have been is Switzerland. It's 99% UK.

I'd like some input, but please be clear about the difference between opinion and fact.
Thanks

No mode S needed in Ireland for VFR. No plans for introduction either.

Opinion: For PRIVATE aircraft Mode S is an infringement of PRIVACY.
Opinion: Mode S should not be necessary for flight within UK uncontrolled airspace.
Opinion: Mode S does not enhance flight safety outside controlled airspace.
Fact: Mode S is not even required in the London CTR.
Opinion: If your aircraft will not fly within airspace requiring Mode S don't bother with it. Apart from the spotters, who is going to be interested in your reg and any other downlinked parameters? Save your money and stick with A+C for ACAS safety.

Mode S and ADS-B will be a requirement for IFR flight in controlled airspace in a couple of years and so your PPL IR member may be a bit stuck then. I would wait until the requirement is introduced as there are product developments in the pipeline that may be cost effective.

Mode S is very useful on our Jodel DR1050. ATC can see the callsign. I've been called "Are you on our frequency yet?" when returning, as soon as I appear on the radar. Fewer radio requests for position reports.

Europe
 

I'm currently in Prague LKPR on a European trip, most larger TMA's in Europe are adopting a Mode S requirement to be able to fly VFR in their airspace. That's why I find it useful as it gives me the 'go-anywhere' ability without having to trawl information about specific aerodromes requirement for fly in VFR. If you're just flying in the UK then it doesn't matter too much but it doesn't mean that the UK won't start implementing the Mode S requirement in the future.

Adding to previous: some countries require mode S for almost all flying. For one example the Netherlands airspace is all TMZ above 1200'. Not that it matters much, the Netherlands is generally not an attractive destination anyway.

Yet it really depends on where you wish to fly.

In the UK TMZ - Transponder mandatory zones - are becoming more common. If you have mode s you can ignore them if you have mode a/c you have to get permission to enter which can be a pain.

I find I get clearance through CAS more easily now I have s over my old a/c - same aircraft.

Mode S is becoming steadily more important in Europe with different states having different rules but it all slowly getting harder to (a) know the differences and (b) fly without s. France is considering changes which may require mode s in class D but this is not a done deal.

In the medium term it is likely that Mode S combined with ADS-B will give considerable advantages for collision avoidance and airspace access. Avoid the Garmin range of units as these will not do Extended Squitter without spending silly money - if at all. Almost all other units will.

Rod1

There is a simpler answer.
If you need to fit a new transponder go for Mode S to avoid having to buy another in a few years time, they are gradually becoming required in more places.
If you already have Mode C dont bother upgrading until you actually need it because they are getting cheaper.

That is certainly the trend we have seen over the last few years. With EASA promising to have more attention for the situation of g/a and recreational flying, couldn't this trend be reversed, or at least slowed down?

@The Ancient Greek: such would be my recommendation, too, if only it were clear where the plane is intended to fly. If a good part of flights are to the continent, it might be more urgent.

Talkdownman I respectfully suggest that you are incorrect in your assertion.
UK AIP GEN 1.5 Para 5.3.1(b) & 5.3.2.1 in conjunction with the ANO Schedule 5 paragraph 3(6)(b) would appear to state otherwise :8
Happy to be convinced otherwise :p

Just to clarify for talkdownman (and maybe others)

First, the simple mode-s that is required for private small planes does not really send that much downlink data, besides altitude, squawk and transponder ID (ac reg).
It is not required to send position or any related parameters.

Secondly, the mode-s protocol is much better and contains both better bit encoding and checksums. This leads to less mistakes in decoding, which leads to better TCAS and better ATC awareness, which leads to better safety for everyone.

I would go for mode-s any time...

Mode S is hardly new, its been around for a quarter of a century now! I'm always amazed at the reluctance to accept new technology once it has be proven to be reliable and of benefit. I can only imagine its that old chestnut of cost making people reluctant to use it.
As stated above mode S is basically A+C with automatic aircraft ID as far as ATC are concerned. In the air its function extends to the aircraft collision avoidance system, a very reassuring bit of kit to have I must say, having had it in my professional life. The more aircraft 'S' equipped there are, the better things are, especially when venturing into "no mans land" outside controlled airspace! ADS-B is the system where there is downlinking of more data for tracking purposes (present position, track, ROC/D etc. etc.) Not sure why that's a privacy issue for private flying though.

The price ticket is perhaps not an issue to you? That makes it easy to be amazed. But no, it wouldn't, to anyone who can afford a Private jet. There are some private flyers around, though, to whom cost is more than a chestnut. Thanks for your consideration.

[[edit]] adding the cost of having to upgrade comm's to 8,33 in the near future, nobody's waiting for another mandatory avionics upgrade.

5.3.2.1 refers only to the London TMA.

TMZ exceptions are detailed in GEN1.5 paragraph 5.3.4, AD-2 EGLD, AD-2 EGTF, AD-2 EGLM, AD-2 EGWU and for Brooklands see EGLL AD 2.22 paragraph 8.

eg. AD-2 EGLD:

Talkdownman,

I apologise for my mistake ref 5.3.2.1.

If I may be so bold, I would think that your original statement
'Fact: Mode S is not even required in the London CTR' should have read
'Fact: Mode S is not even required in some portions of the London CTR', as that is more factually correct.

Thanks for the references, which were an education for me :ok:

Conceded. Shake on that.

Thanks for the inputs so far, please keep them coming.

Of prime concern is the cost of the upgrade, considering that the Mode C is working just fine. The other consideration is that we are going to change the radio (yes we still have one) to an all singing & dancing GPS type navcom on 8.33 separation. That's a bit of a sting.
Doing the Mode S at the same time seems logical, if money were no object. However, the money pits are not bottomless, and the old girl has some other repair/maintenance priorities to be addressed.
All I'm trying to do is to establish the priority ranking of a Mode S.

-Netherlands are now restricted to Dambuster style bombing raids at low level (watch for the pylons!)
-SOME London TMA remains accessible, ie to nominated airfields on the margins.
-The creep of EASA regulations will likely lead to its expectation. Charge the GA flyer, yet benefits accrue to the other users ie ATC and jets.

My query remains one of restrictions and access.

When is the requirement for ADSB likely to come in? That wil be yet another expense, having recently upgraded my unreliable Narco mode C to a Garmin mode S (at the suggestion of my engineer).

Answer to original question:
No.

Surely the IR holder will very rapidly bump into problems without the upgrade?

A le Ron there is no plan that I am aware of to make ADS-B mandatory - it is likely that it will make life easy but it will not be mandatory in class g. The cost of doing ADS-B out if the none certified changes are approved is very low unless you have a Garmin transponder. The cost of doing ADS-B out on my MCR which has an MGL EFIS and a Trig mode s transponder was the cost an rs232 cable.

Which Garmin did you get stitched up with? Some are upgradable.

"Surely the IR holder will very rapidly bump into problems" - like it - no pun intended?

Rod1

As a person on the 'other end' of the SSR can I ask a few questions?

PM me if you want to answer to me privately.

How much is a Mode-S transponder?

How old is your current transponder?

How often do you get your Mode A/C transponder serviced? (Do they check power output, receiver sensitivity?)

The reason why I'm asking is that many older transponders on small aircraft are difficult to elicit a response from (due to some aircraft only having one antenna and the aircraft masks it in a turn and/or possibly poor maintenance) and when the primary is having difficulty in seeing the aircraft too it renders these aircraft as invisible!

So wouldn't a new well-maintained Mode-S transponder make sense?

I found that the cost of a new Mode-S transponder depended heavily on what model A/C you are trying to replace. I had to replace an old A/C transponder some years ago.
It turned out that a company made a mode S transponder that was pin compatible with our old A/C. That was a huge time and cost saver, as the installation took approx 5 minutes, and consisted only of swapping the units.. Of course we had to pay for some testing and paperwork but not having to rewire the cockpit was a big save..

So just a hint to others when you go hunting for a new mode-S. Maybe there exists a pin compatible one, which will save you time and money in the end.

unfortunately i cannot remember the model no of the old A/C.

pottwiddler: your problem may stem from your interrogator being optimised for mode S rather than the transponder in the aircraft. I've read other reports where it says some mode S interrogators don't 'see' mode A/C responses very well; it could even be your software.

Mode s transponders start at around £1700 inc vat. Under LAA rules the unit is tested once a year at permit renewal (and on instalation). It is relativly simple to fit one yourself (on permit aircraft) so fitting cost is zero except for the inspection.

Fitting one to a c of a aircraft depends on a lot of things but ranges from around £400 to £5000!

There are a few plug compatable units as slot-in replacments for the KT76a/c. Typical cost is around £1900 inc vat. With this you simply slide out the old unit and slide in the new!

Rod1

With mode S you become 'visible' on apps such as Flight Radar. Some may like this, some may not.

Shouldn't that read "With ADS-B out active, you become &c " ?

Air Avionics Combined Com/Xpdr Late 2015
 

The head can be shared by both units. Approx 3000 € for both.

AIR Avionics - Butterfly Avionics & Garrecht Avionik - AIR COM - 8.33KHz Radio Systems

This is - sometimes - also true for the simple mode-S transponders that only sends alt/squawk/id.
This is because frlightradar uses a timestamp/triangulation network to get the position of the simple mode-s transponders. But it depends heavily on where you are, as at least 4 triangulation stations must be in view. Here in the copenhagen area it works from 2000 feet and up.
Check out the MLAT section here:
How it works - Flightradar24.com - Live flight tracker!

It appears people take Mode-S for ADS-B, but it isn't. Mode-S is basically A/C plus an aircraft ID, 6 hex digits called ICOA ID, plus a flight ID. The later is commonly set to the callsign in GA (in most parts of Europe you get called by FIS if you enter bogus).

Do you need Mode-S in GA? Yes, you do. There are plenty of places around in european airspace where a transponder is mandatory. While this was unspecific in "the old days", under EASA regulations a transponder IS a Mode-S transponder, nothing else. So, if you travel with A/C only, by regulation you do not carry one. Currently, many or most places with transponder mandatory may grant you entering the airspace, but this is for courtesy and a special clearance (although often not called so) - they do not need to. What many people miss is the requirement for TMZ -> while you are free to enter with Mode-S equipped, you have to call for clearance if you carry Mode-A/C only! Even more, flying in transponder mandatory zones using only A/C transponder may be a violation and you may get fined. Take all the mandatory, equals Mode-S mandatory, airspaces - TMZ, CTR, FL>050 etceteras and you can count 3,2,1 and you are f###ed. I recently encountered several radio situations over Europe when entering a zone was not granted due to missing Mode-S and traffic situation. I do not know the regulations for IFR flight in the UK, but if the AIP states "IFR has to be equipped with transponder", as in other countries and in unified european airspaces, then subconsequently this also makes Mode-S mandatory for any IFR flight. So, if you have somebody progressing toward IR, she/he will immediately call for Mode-S (and may even cover a higher share of the equipment cost in a holders union, what is what we did some years ago - i.e. on top avionics checks to IFR only equipments was paid by the IR pilots, not all).

ADS-B protocol may settle on top of Mode-S with extendes squitter, 1090ES, technology and transmit additional information. There are more frequencies to ADS-B and other technologies, such as UAT in the US or 868 Flarm, but these are not all related to transponder technology. The most prominent additional data can be the GPS position of the aircraft, if and only if the onboard GPS unit is wired to the transponder.

Yes, Mode-S makes anybody listening to the signals aware of your identity, but this is only a quicker way, as your radar trace and a call to your departure field, or look in things as the German Reichshauptflugbuch, will reveal you callsign anyways.

Yes, you will get away without Mode-S for quite a while when flying VFR, but it will depend upon your destinations and FLs. There will be days you are unable to finish your flight as planned due to the missing Mode-S and you have to decide by yourself, when is the time right to put Mode-S in. My advice would be to wait until the first grumble in your stomach appears as a result of a cancelled flight, not earlier. If you failed to get a clearance for a CTR, or a TMZ, or being denied climb FL>050, or if you need service for the transponder broken or not working correctly, it is time for replacement. Until that day your flight profile will not cry for a new transponder. But, be aware if anybody flies to central Europe to check all transponder requirements explicitly on your path upon flight preparation.

Short, I doubt we "need" Mode-S in GA, but there's no way around.

In The Netherlands Mode S is mandatory...

I agree that Mode S is an infringement of privacy and I have always been of the opinion that Mode S for the sake of ATC was mearly a means to identify light aircraft infringing controlled airspace.

Indeed, there are some in NATS who believe that the whole of the South East of England should be a TMZ for this reason.

But now we have the potential of cheap TCAS driven by cheap ADS-B out, surely there is a safety case for ADS-B out even (or more so) in uncontrolled airspace. I don't think you can separate Mode S from ADS-B.

Just looked it up, in France, Belgium and Switzerland as well ...

So, best guess - despite all possible discussions on privacy infringements, surveillance and other things the european citizens allowed by elections - there is no real choice to avoid Mode-S transponder.

@CH & @pirke: I fly in Belgium - and abroad - without any kind of transponder. Fully legal. So please do not make such generalistic blank statements, even legal truth is more complex. Practical reality even more.

Even in them dratted Netherlands TMZ is only above 1200' AMSL.

:(Garmin 328

Anti safety Stupidiry from EASA.
 

The cost of ADS-B out is not very much if you have a home built or have an Annex 2 aircraft.

The problem comes when you are flying an Annex 1 aircraft and are regulated by the anti safety idiots who call them selfs the EASA, then you require an STC, not to fit and use the mode S but to switch on the ADS-B part of the system !

The cost of doing this is IRO £15K ! Just for the paperwork , I did Write to the boss of EASA about this but he did not reply, I guess he is too embarrassed by the stupid situation that has resulted from EASA over regulation and lack of practical industry knowledge.

I can only think that job protection and climbing the slippery pole are far more important within EASA than that GA having an affordable anti collision system.

The written law and what people do are drifting away from each other with increasing speed.

Wot Chickenhouse said

Chickehouse & Abbeville
 

While from a practical standpoint I agree with you completely I do feel that to have a European regulatory authority that's title containers the word "safety" that is by its own sortsightedness and over regulation making it financially punitive to install equipment to make collisions less likely ( rather than encouraging it as the UK is doing) rather defeats their roll as protectors of public safety.

The fact of the matter is that EASA is failing in its duty to promote and regulate better safety standards in European aviation and so in its present state is unfit to regulate.