Dutch ban Mode S under Schiphol CAS

[astir 8]

See AOPA: Home Page (http://www.aopa.co.uk)

in their news section 4th April

Apologies to Mr vanHorck who already got there slightly circuitously by his earlier thread "Ban around Schiphol for GA" but the mind does boggle.

a) Mode S fitting compulsory

b) Mode S causing problems so ban aircraft with Mode S


Any comments from our Mode S enthusiasts?

[Rod1]

I would like to commend the CAA approach to mode S. The CAA may have come up with a very silly and technically impossible proposal, but it did listen and it did change its plans. We do not have mandatory mode s and we are not in the mess.:D

Rod1

[vanHorck]

Mr (!?) van Horck accepts your apologies and commends you on your posting!

Bert
:)

[JKilp]

I wonder how much planning the Schiphol ATC did before the introduction of Mode S transponders. The number of planes based in the Netherlands with Mode S transponders has I suggest not changed significantly in the last year and is known by IVW. The average number of foreign planes transiting the Shipol area is well known from history.So the maximum number of GA planes with mode S to be handled by Amsterdam Information was known in advance. What went wrong! Lack of planning? Lack of investment? Something else?

[Radarspod]

Any comments from our Mode S enthusiasts?

OK, I'll bite.

Let's be clear exactly what the problem is raised by Schipol issue. It is to do with mandatory transponder carriage for VFR in the area, not Mode S itself. Mode S just happens to be the means of compliance. If this was done 10 years ago, then the same problem would have come up with Mode A/C only transponders as the means of compliance, except it would have been a lot worse for ATC due to garbling, etc.

Unfortunately, as I have found common in the past few years (most likely due to the badly handled CAA Mode S consultations), the ill-informed tend to write articles (quite possibly with good intentions) that end up missing the message, giving Mode S a bad name. Mode S isn't the problem, it is the not very well thought through transponder carriage regulation that's the problem.


RS

[chrisN]

RS, why is there a transponder problem at all?

I have seen at Swanwick, re large numbers of radar returns from transponding aircraft beneath London’s LTMA that they filter only the 7000 numbers so...

A 7000 squawk with Mode C would go from...

7000
24
*.......

to...

24
*......

...when filtered (if the email formatting holds up).

I am told that it just cleans up the display a little and the squawk can be seen again by the pushing of a single button that is in easy reach. The radar return is always visible.

If that works for London TMA, why does it not for Schipol/Amsterdam?

[I certainly understand one part of the Schipol rules – winch launched gliders have such a high climb rate for the first 1000 to 1500 feet that it could trigger TCAS alerts to overflying aircraft unnecessarily, hence switch off/standby when launching.]

Chris N.

[Radarspod]

You are right, there isn't actually a transponder problem - I'd suggest in this instance that the ATC provider at the airport in this instance didn't plan ahead and put that kind of filtering in place, hence the Netherlands CAA gave them a few weeks to get it sorted. Just because NATS have the forethought to put this functionality in, doesn't mean everyone else does too :}

Planning, it's all in the planning :ok:

RS

[flyme273]

Following the coast is a popular route for north-south traffic - in particular to Texel.

Problem is if north bound, with this new restricted airspace how does one maintain Right Hand Rule?

flyme

[flyme273]

I see the east of Schiphol route using the Pampus VOR is now also within the restricted area. This VOR always served as prudent protection from staying into Schiphol CTR.

Its all very well for the Dutch Authorities to impose this SRZ in the name of safety due to radar clutter, however it makes GA flights arround the SRZ quite unsafe.

The whole purpose of having a mode S was to receive a traffic service, which in this airspace is very necessary. Now all flights are funneled into less airspace increasing collision risk.

Dedicated flow routes would be an advantage.

[BackPacker]

Problem is if north bound, with this new restricted airspace how does one maintain Right Hand Rule?

Actually, the Right Hand Rule is a UK thing. It's not a rule in NL, nor is it given as sensible advice during a Dutch PPL course. And yes, this surprised me greatly when I started flying in the Netherlands.:eek:

Nevertheless, if you fly exactly over the beach when flying north, and a mile or so offshore when going south, the problem is nicely solved and this seems to be what most people are doing anyway. But yes, keep your lights on, maintain contact with Amsterdam Info and keep a sharp lookout in any case. And mind the gliders near Noordwijk and Castricum.

[Kolibear]

From the Dutch AIP:-

This AIP Supplement introduces the special rules zones Schiphol and Hilversum. These SRZs are created as a result of the radar clutter
due to the increased number of VFR flights with activated mode S transponder under the Schiphol TMA 1. The radar clutter is increased
to such an extent that Schiphol Approach cannot properly provide air traffic control. This radar clutter is a safety problem and is, therefore, not acceptable.
Dutch aviation authorities have therefore decided to clear the area around Schiphol, including Lelystad and Hilversum, from traffic with
activated transponder. For Lelystad and Hilversum, a ‘transponder prohibited zone’ is created. Around Schiphol, a special rules zone (SRZ)
is created. Aircraft with a mandatory mode S transponder are not allowed in this SRZ (exemptions are listed below).
To be perfectly clear: the mandatory carriage of a mode S transponder is not changed.
At this moment, it is hard to assess how long the measures shall be effective. ATC the Netherlands and CAA the Netherlands search for
a solution for the problem. As soon as the solution is found and implemented, these measures will be cancelled

So you must fit a Mode S transponder, but please don't turn it on.

[Aussie Andy]

This is almost funny....!!:rolleyes:

So Mode S is mandated at behest of ATC powers to enhance safety - then NOTAM'd to be not used because it decreases safety!?!? :{

[vanHorck]

Thread with additional info running here
http://www.pprune.org/private-flying/368887-dutch-ban-mode-s-under-schiphol-cas.html

[LH2]

Out of curiosity, could someone provide some background relating to this?

What I wonder specifically is how mode S generates any more clutter than mode C would have used to? Or perhaps VFR GA were not bothering with transponders at all in that area? Just wondering.

[A and C]

My Euro MP will get a letter on this one!

[soay]

The radar clutter issue is discussed in the AOPA forum here (http://forums.flyer.co.uk/viewtopic.php?f=26&t=54089).

[dublinpilot]

So you must fit a Mode S transponder, but please don't turn it on.

I think it's worse that that. If you were required to fit it (ie mandatory) and you did fit it, then you're no longer allowed to go into the SRZ!

[M609]

The Dutch ATC provider has really messed up preparing their radar display system. Most remotely modern Atc systems have a CJI (Controller Jurisdiction Indicator, name and abbreviations vary in different systems) on all known tracks. This means in most systems you can remove the label of the tracks with CJIs not belonging to you (i.e your sector) using the quicklook (or similar) functions of the system.

That way you get only the blip/track on your screen, and MUCH less label garbling problems.

In some systems airspace below a TMA/CTA will automaticly be assigned to the above ATC sector, and all mode C/S tracks below that sectors airspace, wheter it is talking to it or not will get that CJI. (And get label-and you get the garbling)

The way around that is to define the airspace below to another CJI, or define the CJI allocation in such a way that ATC has to "take" control of the track and put it on their CJI if traffic below the TMA for whatever reason in talking to them. Most systems I know of don´t allocate CJI to non discrete codes, i.e 7000/2000/5200 etc, and the controller have to assign a discrete code to get the aircraft on his/her CJI.

In this case the duch must have screwed up royally regarding all the above, and It´s not that far fetched: I´ve seen first hand elsewhere how much noise operational ATC staff has to make to get management/tech support to make critical changes to equipment!

And I have great sympathy for the approach people at AMS, label clutter is VERY distracting to put it mildly. Still, very bum deal for the VFR flights affected.......

[AC-DC]

The Mode S TX. can be turned 'off'. Will this solve the problem or a working TX. is a must?

[astir 8]

And now NATS want TMZ's all round Stansted (for starters):sad:

See the LAA, AOPA or BGA websites for info. Responses to the "consultation" must be in by 17th April - which is tomorrow as I write!

[BackPacker]

The Mode S TX. can be turned 'off'. Will this solve the problem or a working TX. is a must?

AC-DC, yes, turning a Mode-S transponder off would remove the radar clutter: only the primary targets but without any textual information would be displayed on the radar screens.

HOWEVER the Dutch regulator (IVW) decided that maintaining the rule "if you have a transponder you have to turn it on" was more important so they decided to ban everybody who happens to have a serviceable transponder from that bit of airspace

And yes, the irony is that if you do not have a (serviceable) transponder, you cannot turn it on (obviously) so the SRZ doesn't apply to you.

Rumour has it that this was not the solution that was proposed by the Dutch ATC provider (LVNL) and obviously the organizations representing GA (AOPA NL, KNVvL) were not happy with it either. There was a meeting last Friday with all the organizations I mentioned (and maybe a few I missed) to discuss things and the proposal is now to keep the SRZ in place but only between 1200' and 1500', and below 1200' revert back to the former practice of turning the transponder off. All organizations have now taken this proposal back to their respective bases for comments, and after a further round of talks (I think scheduled for tomorrow) it may well be that the whole situation is going to change on a very short notice.

Vandaag 10 april hebben de Sectorpartijen van de Stuurgroep General Aviation, in een gezamenlijk werkoverleg met de luchtruimexperts van Verkeer en Waterstaat en Luchtverkeersleiding Nederland, op basis van de beschikbare analyses, gewerkt aan het ontwikkelen van alternatieve veiligheidsmaatregelen voor het luchtruim onder de SPL/TMA 1, met het oogmerk de negatieve effecten voor de General Aviation zo veel als mogelijk te beperken.

Uitgangspunt hierbij was een veiligheidsborging tegen de luchtruimschendingen van ongewenste indringers en het tegengaan van clutter op de radar van de naderingsverkeersleiding. Partijen zijn het er over eens dat als er maatregelen genomen moeten worden deze bij voorkeur gerelateerd dienen te zijn aan de bestaande luchtruimindeling en dat het onwenselijk is nieuwe gebiedsgrenzen te introduceren.

Consensus bestaat over het tijdelijk invoeren van een nieuwe beperking onder de SPL/TMA 1. Bij de diverse diensten wordt thans getoetst of het instellen van een maximum vlieghoogte van 1200ft onder de SPL/TMA 1 voor VFR –verkeer zonder werkende transponder het beoogde effect oplevert. Alle verkeer wordt ten sterkste aangeraden uit te luisteren op Amsterdam Info.De zone tussen de 1200ft en 1500ft blijft in dit voorstel op basis van een toestemming van LVNL beschikbaar voor met name genoemde categorieën maatschappelijk en/of urgent verkeer. Het spreekt voor zich dat ook de sectorpartijen zullen toetsen of de beoogde maatregel tegemoet komt aan de eerder geuite kritiek op de BVG SPL en voldoet aan de veiligheidsnormen die de GA zichzelf stelt.

De experts zijn het met elkaar eens dat de gepubliceerde procedures voor vertrek en aankomst bij luchthavens, die onder de SPL/TMA 1 liggen onverkort dienen te worden gehandhaafd en in principe niet mogen worden overruled door de af te kondigen generieke veiligheidsmaatregel.

Naar verwachting zal de nieuwe maatregel eind volgende week worden afgekondigd. Tot de nieuwe maatregel in werking treedt blijft de beschikking van de Minister en daarmee AIP SUP 04/09 d.d. 04 APR 09 onverkort van kracht.

Source: AOPA.nl

[BackPacker]

As of tomorrow (April 25th) the SRZ Schiphol rules will change.

Most important changes:
- The SRZ is extended laterally to lie below the full Schiphol TMA 1, excluding the EHAM and EHRD CTRs, the North Sea Area and the ATZ/SRZs of EHLE and EHHV.
- Motorized VFR traffic carrying a mode-S transponder is now again allowed to fly in the SRZ below 1200', with the transponder switched to standby.
- The area between 1200' and 1500' is considered a buffer to avoid infringements and traffic warnings. Essentially for this altitude band the original SRZ rules remain unchanged.
- The SRZs for EHLE and EHHV remain unchanged.

So good news, finally! Well done AOPA, KNVvL, LVNL, IVW and all other parties involved in the process.

[Warped Factor]

Barking!

What good is TCAS and any other electronic aids if transponders are mandated off?

Absolutely barking!

[bookworm]

Barking!

To describe this issue in that way is an undeserved slur on rabid dogs.

[PiperCubFlyer]

- Motorized VFR traffic carrying a mode-S transponder is now again allowed to fly in the SRZ below 1200', with the transponder switched to standby.

So they have made the vast majority of any 'safety nets' mitigating the consequences of a vertical infringement of controlled airspace, completely useless.

Madness, if not negligent IMHO.:=

[BackPacker]

So they have made the vast majority of any 'safety nets' mitigating the consequences of a vertical infringement of controlled airspace, completely useless.

For those of you just stepping in, a quick summary.

The problem started when on the first fine day this spring everybody in possession of a PPL started to go out and fly, particularly in the triangle between PAM, EHLE and EHHV. Since everyone fitted mode-S in the last few months and since the ban on operating your transponder underneath the Schiphol TMA-1 was lifted recently, this lead to an enormous amounts of labels appearing on the radar scopes of the controllers working Schiphol Approach.

This lead to an immediate safety problem, because the controllers couldn't distinguish their own traffic in the TMA-1 from all the traffic underneath the TMA-1. And this lead the IVM (the Dutch CAA) to introduce the SRZ, which basically banned all GA/VFR traffic from underneath a large portion of the TMA-1 wholesale. In fact, it effectively sealed off about 20% (laterally) of the Dutch airspace from GA/VFR traffic.

The fundamental problem of radar clutter is not solved yet, and will likely take a few more weeks. But because of the negotiations between the various interested parties at least we have access to most of the airspace underneath the TMA-1 again, albeit without the safety net of a transponder. But that's a situation we were used to in any case, since until about a year ago, usage of a (mode A/C at that time) transponder was forbidden underneath the TMA-1 anyway.

Personally, I'd rather have access to a fairly crucial bit of airspace with the restriction that my transponder needs to be turned off, than have no access at all. At least this way I can make my safety trade-off myself.

Now you UK folks can all sit back and look at the crazy Dutch guys for implementing and reversing measures like this within weeks, but fundamentally the situation in the UK is not much different. You've all gotten a delay in the mandatory implementation of mode-S, compared to the Netherlands GA scene, but at some point in time the UK GA fleet will have to implement mode-S wholesale as well. Unless NATS is really on the ball and learns from the Dutch mistakes, you will get the exact same situation around the London zone, where dozens, if not hundreds of GA planes fitted with their brand new mode-S transponders will take to the skies on the first lovely day of spring, completely overwhelming the radar displays of the London controllers. DET, LAM, BIG, OCK and other VORs around the London zone are very convenient navaids for VFR traffic around the London zone, but they are also very important fixes for almost all the IFR procedures into the London airports. Unless NATS has ideas or filters that the Dutch LVNL does not know about (hardly likely), NATS will get overlapping labels wholesale as well and will have the same problems sorting out their traffic as the LVNL. And their short-term solution may well be the same: ban all GA traffic underneath the London TMA.

[PiperCubFlyer]

Unless NATS has ideas or filters that the Dutch LVNL does not know about (hardly likely), NATS will get overlapping labels wholesale as well and will have the same problems sorting out their traffic as the LVNL. And their short-term solution may well be the same: ban all GA traffic underneath the London TMA.I believe NATS already have the necessary filtering ability to 'filter' data blocks associated with radar tracks in a variety of ways while retaining the tracking symbol and all the functionality related to other tools i.e. Controlled Airspace Infringement Tool, Short Term Conflict Alert and ACAS/TCAS.

I agree that the Dutch problems should act as a wake up call to all ATC providers and regulators about the possible implications of universal transponder equippage and operation. However, I maintain that by literally switching off the 'safety nets' facilitated by the operation of transponders even for a temporary period is madness in comparisson with the risk of an undetectable vertical infringement of controlled airspace especially in such constrained airspace.

[mm_flynn]

Backpacker,

I think one of the reasons (beyond the normal interest people have in witnessing a mindboggling cock-up) the UK fraternity is so interested is when mandatory Mode-S was proposed, many GA people and organisations said,

'With all those new returns you guys (ATC) will never be able to do your core job'.

And the CAA and controllers said (sometimes in the tone used for a small child who just isn't understanding),

'ATC systems have a filtering system that will just show a minimal amount of data, but still feed all of the data into the conflict alert system, and if we need to see your data it is just a mouse click away - there will be no problems with too much data - Trust Me'

Either the Dutch have a staggering lack of foresight and forgot to talk with their European Colleagues (or bought the cheap version of the ATC software) or there is a latent problem. Most GA pilots, myself included don't have the necessary knowledge of how ATC systems work in each of the effected geography to know if this is a one off stupendous cock-up by the Dutch or a systemic problem.

[PiperCubFlyer]

mm_flynn says Most GA pilots, myself included don't have the necessary knowledge of how ATC systems work yet you apprrently have sufficient knowledge to determine that controllers are contributing sometimes in the tone used for a small child who just isn't understanding

[mm_flynn]

One doesn't need a detail understanding of the software, hardware and organisational implementation of ATC systems across a number of service providers to be able to have an opinion on the tone of someone's communication. All that takes is to listen to their presentations, answers to questions from the floor, written documents, posts (which of course may or may not actually be ATC people) and 'offline' conversations.

My experience during the whole Mode-S process was that the people driving it and desiring it were getting very frustrated by GA organisations and individuals arguing that, they (predominantly the CAA), hadn't thought it through and the implementation would be like the Dutch experience. You could see this frustration coming out in the tone of answering the same question the 300th time.

My comment wasn't meant to criticise controllers (who I find generally do a fantastic job), but was meant to re-enforce the message GA have been categorically and repeatedly assured by the CAA, NATS and many individual controllers that the Dutch problem was not going to happen. The message was not couched in terms of we are OK in the UK but it may well be a screw-up over there in Europe. So I believe was reasonable to apply the CAA assurance to the project as a whole.

[jxk]

But if the data is going to filtered out most of the time and only going to be used if a conflict is detected then why isn't the mode A & C good enough?
As I see it mode S does nothing to help or provide additional service to most of GA and hence the reluctance to spend 3/4K. eg - Here I am in class G airspace bumbling along - may have a nearby LARS tuned in and a corporate jet is deadlegging back to base in the same airspace, who is going to warn either of us about a possible confliction. In these circumstances mode S buys you no more than A & C.

[mm_flynn]

But if the data is going to filtered out most of the time and only going to be used if a conflict is detected then why isn't the mode A & C good enough?

The main reason (as I understand it) that Mode-S is important is - With an increase in transponder usage (due to mandatory fitting, TMZ, good practice, etc.) at some point the number of Mode-A/C returns on the single frequency will cause excessive interference. What that point is I don't know.

I do know that powered aircraft density (all with transponders) is much higher in the NY and LA than in any European TMA and the US has not needed to mandate Mode-S. However, the US may have a more efficient radar infrastructure and therefore generate less returns. Also, non-powered (i.e. no-electric) aircraft are more popular in Europe and the total of electric and no-electric aircraft operating under the TMAs may be greater than the US experience.

Mode-S addresses this problem by only answering when it is asked, so the SSR unit can sort out all of the targets easier (for example the SSR unit says, whose there?, gets the list then says, all you on the list stay quite, who is there? and this picks up any response that were originally masked).

In addition, all of the ACAS units out there are also interrogating transponders and creating frequency congestion. As the price comes down these are being fitted more frequently. ACAS/Mode-S creates much less load on the SSR frequency than ACAS/Mode-A/C.

Also, the price is coming down, it is unlikely to be £3/4K more in the low £2k - maybe even less if you shop around.

[PH-UKU]

Also, the price is coming down, it is unlikely to be £3/4K more in the low £2k - maybe even less if you shop around.

Well I've just put in a Filser TRT800 (which I reckoned was the lightest, cheapest and most future proofed .. (ADS-B compatible)). The kit cost £1800 and the mod/paperwork took it all up to £2500.

My experience during the whole Mode-S process was that the people driving it and desiring it were getting very frustrated by GA organisations and individuals arguing that, they (predominantly the CAA), hadn't thought it through and the implementation would be like the Dutch experience. You could see this frustration coming out in the tone of answering the same question the 300th time.


I agree that the tone from the CAA and those doing presentations can be annoyingly patronising, but please distinguish between NATS (and other ANSPs) operational controllers who just have to get on with the job, and those who are out to make names and empires for themselves in the name of safety.

I understand that several that were pushing this are ex-RAF Fighter Controllers (who come from a mindset of trying to spot/identify and pigeonhole every 'target' as a 'threat'). [please note there is a BIG difference between Fighter Control and Air Traffic Control].

As an operational ATCO, and flyer, I strongly objected to the Mode S mandate particularly on the grounds that it would over-clutter my screen. When we have 24000 registered flying devices in the UK at the moment, and only about 8000 have transponders, it doesn't take a rocket scientist to predict what is liekly to happen when another 16000 are installed and then switched on!

Personally I don't think many of those in the CAA have much relevant practical experience of civil controlling or understand the problems, it all seems to be staffed by ex-RAF these days (not that I have anything against that ... being one myself..)

Off to lie down ............

[vanHorck]

According to an AOPA NL publication the sole reason for banning VFR traffic under the Schiphol TMA was because switching the mode S off to declutter the screens would have meant that the ministry of transport would no longer be able to detect infringements!
The recommendation was made by the ATC guys and girls to switch to stand by mode but the Ministry refused (initially).

What a disgrace!