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Mode S: do we need it in GA?

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Mode S: do we need it in GA?

Old 11th May 2015, 08:37
  #21 (permalink)  
Join Date: Jun 2007
Location: Swindon, Wiltshire
Age: 44
Posts: 862
One or two members have IMC rating, in fact one is progressing to PPL-IR.
Surely the IR holder will very rapidly bump into problems without the upgrade?
stevelup is online now  
Old 11th May 2015, 09:18
  #22 (permalink)  
Join Date: Apr 2003
Location: Midlands
Posts: 2,361
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 is offline  
Old 11th May 2015, 10:15
  #23 (permalink)  
Join Date: Aug 2007
Location: The glasshouse, a stone's throw from you
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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?
pottwiddler is offline  
Old 11th May 2015, 14:04
  #24 (permalink)  
Join Date: Aug 2009
Location: Copenhagen
Posts: 149
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.
lasseb is offline  
Old 11th May 2015, 16:39
  #25 (permalink)  
Join Date: Nov 2005
Location: River Thames & Surrey
Age: 71
Posts: 8,421
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.
chevvron is offline  
Old 11th May 2015, 18:06
  #26 (permalink)  
Join Date: Apr 2003
Location: Midlands
Posts: 2,361
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!

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Old 11th May 2015, 19:13
  #27 (permalink)  
Join Date: Apr 2015
Location: Rochester
Posts: 21
With mode S you become 'visible' on apps such as Flight Radar. Some may like this, some may not.
RO13FLY is offline  
Old 11th May 2015, 20:11
  #28 (permalink)  
Join Date: Jul 2010
Location: EBZH
Posts: 2,509
Shouldn't that read "With ADS-B out active, you become &c " ?
Jan Olieslagers is offline  
Old 12th May 2015, 01:07
  #29 (permalink)  
Join Date: Sep 2001
Location: Toronto
Posts: 2,235
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
RatherBeFlying is offline  
Old 12th May 2015, 06:58
  #30 (permalink)  
Join Date: Aug 2009
Location: Copenhagen
Posts: 149
With mode S you become 'visible' on apps such as Flight Radar. Some may like this, some may not.
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!
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Old 12th May 2015, 08:17
  #31 (permalink)  
Join Date: Mar 2014
Location: The World
Posts: 1,227
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.

Last edited by ChickenHouse; 12th May 2015 at 13:45.
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Old 12th May 2015, 09:25
  #32 (permalink)  
Join Date: Mar 2014
Location: Netherlands
Posts: 162
In The Netherlands Mode S is mandatory...
Pirke is offline  
Old 12th May 2015, 10:21
  #33 (permalink)  
Join Date: Dec 2010
Location: Back in the UK again.
Age: 73
Posts: 170
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.
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.
Bob Upanddown is offline  
Old 12th May 2015, 11:10
  #34 (permalink)  
Join Date: Mar 2014
Location: The World
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In The Netherlands Mode S is mandatory...
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.
ChickenHouse is offline  
Old 12th May 2015, 16:01
  #35 (permalink)  
Join Date: Jul 2010
Location: EBZH
Posts: 2,509
@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.
Jan Olieslagers is offline  
Old 12th May 2015, 17:46
  #36 (permalink)  
Join Date: Feb 2011
Location: Leeds
Posts: 54
Garmin 328
A le Ron is offline  
Old 12th May 2015, 18:52
  #37 (permalink)  
Join Date: Jan 1999
Location: north of barlu
Posts: 6,180
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.
A and C is offline  
Old 13th May 2015, 07:34
  #38 (permalink)  
Join Date: Mar 2014
Location: The World
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The written law and what people do are drifting away from each other with increasing speed.
ChickenHouse is offline  
Old 13th May 2015, 14:54
  #39 (permalink)  
Join Date: Mar 2001
Posts: 154
Wot Chickenhouse said
Abbeville is offline  
Old 14th May 2015, 04:48
  #40 (permalink)  
Join Date: Jan 1999
Location: north of barlu
Posts: 6,180
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.
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