AFAICT most/all “ATC capacity” slots assigned to light GA are algorithm artefacts and not justified operationally. One ATCO told me a sector capacity of say 30 is reached if there is 1 PA28 at FL100 and 29 747s at FL300.
achimha wrote:
The reason why I think Peter’s action was justified and why I personally would have done the same thing is that the IFPS rules required filing via Zurich where the CTOT originated (as shown in the CTOT message which I saw) but I knew before the flight that Skyguide would not route this flight via Zurich, therefore the CTOT was unrealistic.
I’m not debating whether Peter’s action are justified or not. As I said what matters on this subject is Skyguide’s opinion.
I’m only explaining how ATFCM works with illustrated example, I’m far from being competent as judge 
.
Peter wrote:
One ATCO told me a sector capacity of say 30 is reached if there is 1 TB20 at FL100 and 29 747s at FL300.
This is rather airspace specific. If that’s the same sector which handles traffic from FL100 to FL300 that’s possible (unlikely in France).
I should also point out that even though the FP was filed several days before EOBT, the CTOT was generated as I was walking to the aircraft! In many GA scenarios, the pilot would be airborne before discovering it. Then what is he supposed to do?
This is very poor.
Peter wrote:
I should also point out that even though the FP was filed several days before EOBT, the CTOT was generated as I was walking to the aircraft! In many GA scenarios, the pilot would be airborne before discovering it. Then what is he supposed to do?This is very poor.
Well, that’s mostly because you fly a very slow aircraft, it was hours from reaching Zurich… It can happen much later, we frequently see 30 min before EOBT.
Peter wrote:
Then what is he supposed to do?
On towered airfield it’s obvious – he will not get startup clearance. It happened to me once at LYBE on Croatian ATC request CTOT was generated for one hour later than filed EOBT. I was already in aircraft when I got info. On non-towered airfield I don’t know – probably I would do as required, delaying my departure.
Now let’s assume you are not on the internet with your phone – like perhaps 75% of the GA community which is not on EuroGA or like all of us say 10 years ago.
because you fly a very slow aircraft, it was hours from reaching Zurich
I don’t see the relevance of the TAS because you cannot possibly be expected to land somewhere for an hour or two.
Then it’s not only up to you, ATC as well has to help you in finding solution. You’re in the air asking for IFR clearance and they can’t simply send you back (e.g. because the airport you took off is already closed) or to some other airport (because it’s not something that you planned or obliged to do). So I guess they would find a way to squeeze you somehow via route you filed or via slightly changed route.
Peter wrote:
I don’t see the relevance of the TAS because you cannot possibly be expected to land somewhere for an hour or two.
You can only get CTOTs before departure obviously. The projected congestion was hours away from your EOBT and you were not very high on the list of aircraft to penetrate the regulated sector which is why you got the long CTOT. Most likely the majority of the other planes were on RPLs (repetitive flight plans) which presumably are put in the front of the queue. The congestion usually becomes “visible” not earlier than 4 hours in advance and that’s where your low TAS plays a role — you were hours away and therefore got it relatively late relative to your filed EOBT.
The Zurich area is notoriously bad for GA overflight, best try to avoid it. There are sectors with extremely low capacity, 2-3 aircraft only in my estimation.
Now let’s assume you are not on the internet with your phone – like perhaps 75% of the GA community which is not on EuroGA
The most widely used GA IFR filing solutions are RocketRoute, EuroFPL, autorouter and the national AIS. All of them relay they CTOT messages. I don’t believe your 75% figure is anywhere close to reality.
One of the reasons I file the FP a few days ahead if possible is because CTOTs are allocated approx EOBT minus 3hrs and are handed out on the basis of the latest filers getting them first. That is according to one Eurocontrol document I have seen. Maybe they changed that…
ATC calling in sick or going on strike probably results in a CTOT for everybody, no? If not, their algorithm is poor because light GA at say FL150 is going to be no issue at all operationally.
