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-   -   Air Traffic Control out in Sweden (https://www.pprune.org/atc-issues/570294-air-traffic-control-out-sweden.html)

Klauss 7th Nov 2015 16:41

Air Traffic Control out in Sweden
Hi, I read newspaper articles that there was an outage of air traffic control in Sweden on the 4th of November. Anyone have Details ? What didnīt work anymore ?
Thanks .

LookingForAJob 7th Nov 2015 17:46

Everything stops? If only the radar was affected what's the problem getting a few off procedurally? Or doesn't anyone know how to do it any more?

Una Due Tfc 7th Nov 2015 17:51

Procedural isn't taught in many places anymore, and how comfortable would you be sitting down with paper and a pencil and doing it for the first time in a few decades with live traffic?
I certainly wouldn't be.

G0ULI 7th Nov 2015 17:55

There are no procedures except land as soon as possible.
If the geomagnetic disturbance from the flare is severe enough, radio doesn't work, radar doesn't work, and GPS signals are lost. Radio based navigational aids will also fail or be unreliable.

So strict VFR flying conditions with no external contact between aircraft and the ground or other aircraft and no navigational information except eyeballs and paper charts. Even that may not work if compasses are inaccurate, as they often are that far north in geomagnetic storm conditions.

Still want to fly?

Sometimes we just have to recognise that nature is bigger than our technological solutions.

LookingForAJob 7th Nov 2015 18:26

Mmmm, the irony - which is behind only part of my comment - doesn't travel well in text.

For a more serious bit of input, I hope that the GPS stuff comes back when the solar disturbance has passed. The rate at which ground based navaids are being removed and at procedures are introduced that are reliant on space-based systems, leaves the entire aviation system vulnerable because nature is bigger than anything that we make.

But it will be OK, in Europe at least - the politicians have set up the EACCC.

But back to my original point for a moment, I know procedural control isn't taught much any more. And I know that the experts don't trust the sort of controller we have in Europe to do procedural control. But even the most inept controllers among us should be able to work out when aeroplanes are 1000ft or 2000ft apart vertically and 10 minutes apart longitudinally. And being able to do that should be a basic skill for any controller because that radar that we rely on is built by humans too!

kcockayne 7th Nov 2015 18:44

Procedural really ought to be taught & be available. However, keeping proficient enough to be able to use it I in a serious situation with lots of traffic is problematical. it was abandoned partly because of the reliability of Radar systems, but also as a cost saving matter. I think that the cost saving element was given far too high a priority & that Procedural training should have continued.
I also have to reflect that when undergoing TRUCE training, ATCOS at my unit, who had no experience of controlling without SSR, were at a complete loss of how to continue Radar Control using PRI only. This is highly regrettable & ought not to be allowed. But, that is the modern way, & every penny counts !

055166k 7th Nov 2015 19:15

You may find that London Control is not authorised to provide a non-radar service except for short term clear the sky purposes.

LookingForAJob 7th Nov 2015 21:10

You may find that London Control is not authorised to provide a non-radar service...
Quite so - and many other places also.

Maybe I'm now one of those dinosaurs that I used to complain about in my youth! Like the ones that used to say that SSR was just 'nice to have' and made life a bit easier.

kcockayne 7th Nov 2015 22:17

I have to admit that it is very hard to imagine any effective sort of Procedural Control taking place in the very busy, & complicated , airspace that we have now. But, it would be a useful tool for ATC to use to provide some sort of service when Radar is u/s. Although, it should be possible to provide back-up Radar within a short while of a failure in the service.
Let's face it, if the Radar fails in busy airspace, it is an emergency situation which can only be resolved effectively by the use of a replacement Radar service. But, I continue to feel that Procedural experience & ability could help in the provision of a safe contingency ATC service, both in the immediate aftermath of the Radar failure & in the longer term, before the Radar is restored.

Klauss 8th Nov 2015 04:16

hmmm....so, Radar didnīt work, and the newspaper didnīt mention GPS. I guess that worked fine, then. Were any notams out ?
Procedural control must be quite difficult with many planes in the sky.... I think Iīd like to stay out of and area where this is done, if I had a choice.

NiclasB 8th Nov 2015 09:09

A friend of mine who works at Sweden Control (but was not at work during the incident) tells me that the MSSR system (1030/1090 MHz) was compromised such that the same aircraft could be displayed up to 10 times along a 20-30 mile track. The disturbance was "medium", which is ironic; if the disturbance had been stronger, the system would have filtered out the bad echoes by itself. The "medium" strength probably explains why the event was not accompanied by increased auroral activity. We've had a few aurora nights at 64N in the recent weeks, but this clear night showed none (bummer).

My friend also stated that procedural routes have either to be purely VOR-based or defined (and approved by the authorities) as "separated", neither of which is common in Scandinavia any more.

Overflying traffic was not affected as they could easily be separated by altitude.

I have heard no report of affected GPS signals nor observed any unusual anomalies (on the ground) myself. Since GPS operate near MSSR frequencies, it would be expected that it too experienced anomalies. My speculation is that if GPS was less largely hit, the difference might be explained by the difference in signal travel direction between MSSR (effectively horizontally) and GPS (more slanted towards vertical, even at 60+ deg north).

His comment that the radar system can filter out strong disturbances intrigues me. Could this be an "automatic" effect because the return signal would appear outside some tight tolerance defined by the Mode A/C/S protocol or is it more likely it is handled in an additional software layer? Any comment from an RF/MSSR-knowledgeable person would be appreciated.

(Edit) The end result was that aircraft in the air were allowed to land but no domestic aircraft were allowed to take off. Don't know about international departures. Normal OPS were restarted after about 1.5 hours. (/Edit)

(Edit 2) After re-reading the media report of that day (http://www.dn.se/nyheter/sverige/sol...ll-radarstopp/) I can add the following: All radar stations that were affected had the sun above the horizon. All false radar echoes appeared within an 8 degree narrow sector in the sunward direction. (/Edit 2)


LookingForAJob 8th Nov 2015 09:31

Interesting comments. Especially a hint that pilots may not trust procedural control.

Of course there is no way that procedural ATC can handle anything like the traffic levels that are possible with radar.....but procedural control works and is still used in some places on a daily basis. But as has been indicated here, it often isn't taught to new controllers today - or in one situation that I saw, a two month training course was replaced with a three hour lecture and one simulator session (more to show the trainees how 'difficult' it is than anything else).

To my mind there is a parallel with the debate currently being had in the airborne side of the system. Pilots that are trained today are often trained (and probably very highly skilled at the end of that training) to operate the aircraft using the computer control systems. There are claims that some new pilots do not have a great deal of exposure to basic flying skills and lack the experience and knowledge to recognise when things are going wrong. Likewise, there is evidence that there is a belief held by some that the aircraft will never lie to them and consequently they may not look for the basic cues that will help analyse what the aircraft is doing.

The training system is, in places, turning out people whose level of experience does not enable them to do the basics, but can control a huge machine incredibly accurately using the tools provided by the manufacturer. This works well most of the time and enable a fully serviceable aircraft to be flown exactly as wanted and with great efficiency. This is fine, particularly for the beancounters who have a great say in how airlines are run (I don't mean this in any way disparagingly, doing things efficiently is very often good). These same beancounters are happy because the training is focused on what is needed - the need to know rather than the nice to know - and the training is cost-efficient too. Every now and then, typically during some refresher training there will be an exercise to check basic skill or give some practice in something basic, that we all assume everyone knows about - and a box gets ticked.

And in recent years we have had similar principles applied to ATC.

The upshot is that when all of the systems are working properly, everything works fine. But when things start to go wrong, the people we trust to sort it out may be woefully unprepared to handle it....and, in the worst outcomes, people die. The question is, is 'society' (and in particular the passengers on aircraft and those living under the routes followed by aircraft) prepared to accept that very, very occasionally aircraft will crash because of human intervention or lack of it, into a combination of events that is incredibly unlikely, in statistical terms, to occur. The answer appears to be yes, judging by the ever-increasing numbers of people who travel by air, particularly using the LCCs.

And all this, supported by regulators, where they are effective, that are more interested in seeing boxes ticked that how things happen in the real world.

OK, rant over. I think I smell the Sunday breakfast nearing the table.

kcockayne 8th Nov 2015 13:06


I could not agree with you more ! I know that the statistics give comfort to "those that matter", but they give no comfort to me. As I have said before, my generation of ATC was schooled (& submersed) in the "when the system fails, it fails safe" philosophy. For me, it is difficult to imagine that this philosophy is upheld in modern systems & methods. However, it is difficult to accuse those in charge of having a cavalier attitude in this matter when the statistics do not make an obvious flaw in safety standards apparent.
I do believe that there is such a flaw underlying the system, but it may never make itself obvious to the ANSPS, the regulators, the bean counters, the general public, or even to the ATCOS. Long may that continue to be the case !
In general, it may have to be accepted that the modern system & philosophy of ATC is the ONLY way to deal with the traffic load. In that case, "Goodbye Procedural ATC".

exlatccatsa 8th Nov 2015 14:26

Sumburgh, Shetland Islands also had a radar outage for about an hour at the same time.

LookingForAJob 8th Nov 2015 16:00

Originally Posted by exlatccatsa
Sumburgh, Shetland Islands also had a radar outage for about an hour at the same time.

Well that will not have been a problem. I know they have procedures (or at least had, I can't imagine they've done away with them) for how to deal with a radar outage!

Klauss 9th Nov 2015 07:31

hmm, shetlands, too ? Well, they are about at the same N latitude as Sweden.
I wonder why Norway and Denmark didnīt have Problems... Found a solar Radio
burst on https://twitter.com/thesuntoday , but donīt know if it is relevant

Re procedural control: canīt really remember having flown that for real during the last decades. So, no real practice - and I donīt think that todays traffic could be handled procedurally.....in London, Frankfurt, Stockholm...


NiclasB 9th Nov 2015 12:35

Klauss, thanks for the link. The timing and length of the event in the plots is consistent with the outage. Too bad that the monitored frequencies stop at 400MHz, but it stand to reason that the 1GHz band was affected too.

oblivia 10th Nov 2015 04:25

This is fine, particularly for the beancounters who have a great say in how airlines are run.
The chief executive runs the company 100%. Except when someone needs to be blamed.

Klauss 10th Nov 2015 05:03

I think so, too, but I am still looking for evidence. There are a few other stations that Monitor to 800 Mhz, but they donīt seem to have the same burst . No idea why....not a scientist....

MrSnuggles 10th Nov 2015 11:56

I wrote about this in the Nordic Forum when it happened.

The people from Luftfartsverket claimed that the solar flares disturbed radar enough that it would sometimes show doubles of planes, and sometimes the planes disappeared.

The disturbance lasted about four hours plus minus. It was low intensity flares so the automated system didn't filter the erroneous data because it was calibrated for larger events.

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