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What is special about FL300 across Germany (at least)?


Janet Kino

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Janet Kino

I was practicing checking flight plans, and for a flight from EGPH to EDDB I discovered something I don't understand.  I'm sure there is some special rule that covers it.  The non-UK portion of the route was LAMSO DCT EVELI DCT OSN L980 HLZ P12 BATEL T207 OGBER.  Validating the route through the NOP portal, if flown at FL300 down to FL260 (since cruising below FL260, once you leave UK airspace, is not allowed), you had to descend to FL240 or lower at HLZ to meet the requirements of P12, BUT if you flew above FL300 you until BATEL to start you descent.  What is special about FL300 over that portion of Europe?

Edited by Janet Kino
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Trevor Hannant

From BATEL to OGBER, the airway itself extends sufficiently high to allow you to fly FL320 or above however you'd need to replace P12 with DCT.   Before that however there's some restrictions that have codes to enable you to check against the RAD, so even planning at FL340 until HLZ generates errors for me:

PROF204: RS: TRAFFIC VIA EDR302BCZ:F245..F660 [202109101130..202109101315] IS ON FORBIDDEN ROUTE REF:[EDR302BCZR] RAD APPENDIX 7 / AREA ACTIVE BY AUP/UUP
 
PROF204: RS: TRAFFIC VIA EDR302BCZ:F245..F660 [202109101130..202109101315] IS ON FORBIDDEN ROUTE REF:[EDR302BCZS] RAD APPENDIX 7 / AREA ACTIVE BY AUP/UUP
 
PROF205: RS: TRAFFIC VIA EDR302BCZ:F245..F660 [202109101130..202109101315] IS OFF MANDATORY ROUTE REF:[EDR302BCZT] RAD APPENDIX 7 / AREA ACTIVE BY AUP/UUP

If you search for 'EDR302BCZS' in the RAD (link here) then it may tell you what the reason is for that (sometimes!).  Sometimes it's due to military airspace potentially being active, sometimes they don't give a reason.  Sometimes a specific routing isn't allowed for specific airport arrivals or on specified days/times.   

Know that doesn't give you a specific reason for this case but that's a good starting point to look at.

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Janet Kino

Thanks Trevor.  I didn't receive, and still don't receive, any error messages about FL340, but that could just be time-of-day/day-of-week stuff.   I didn't think of the possibilities of flying direct there... too focused on what the pilot had actually filed, I guess.  I'll dig deeper into the RAD and also see if, by changing altitudes and doing validations, I can't get some more information from the error messages. 

I find that the RAD tends to give me too much information (Do This, unless That, except for the following 6 situations, in which case, Something Else, unless it is a Blue Moon, in which case no one cares, because ATC is all out looking at that anyway).  Looking up EDR302BCZS in the RAD gives you one of those no flying at all unless in the following 9 exceptions sorts of answers.  If you Google, it you will be shown an extremely dense map that has been OCR'ed.  I figured it all out eventually, but it certainly isn't something that anyone could do while trying to approve a flight plan.

I wonder how long (in nm) before they get to EDDB does the pilot need to smoothly descend from those levels?   I assumed that was what was starting at HLZ, but perhaps it can be put off until later.

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Simon Kelsey

Just to add to the above, I don’t know for certain but FL300 feels likely to be the sort of point where you might expect a vertical division between ATC sectors as well, so this will affect route restrictions as well (to keep traffic to certain destinations out of/in specific sectors etc).
 

To answer your question about how far an aircraft requires to descend, from FL300 approximately 110NM would be required (assuming an airport at/near sea level). The usual method used by pilots is to take the height to lose in 100s of feet and divide by 3, so 300/3=100 and, starting from the cruise, I’d add a bit (about 10NM) on to allow for the fact that we will need to slow down as well. If there were a tailwind I’d add some more on, and with a headwind take a little off (1/3 of the head/tailwind component is a good figure). But to estimate for air traffic purposes the 3x table is good enough!

Edited by Simon Kelsey
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Janet Kino

Thanks too, Simon.  Your response also helped shed so light on what might be going on.  There is a UIR change between HAZEL (HZL) and BATEL.  Using your suggested descent distance numbers, the pilot would probably want to start their descent from FL300+, between HZL and BATEL, and after BATEL everything is leading you into Berlin, so my eyeballing of what whoever designed the plan originally thinking, may have been correct in my assumption about where the pilot might have been planning to start their descent.  

 When a pilot files a flight plan with a speed/altitude change shown at a waypoint, are they saying that they are planning to start the change there, or be done with it there?  If they are coming down from an Upper Airway to a Lower Airway, are they expected to be at the correct maximum altitude as the join the lower airway or do they slide on down into it?  I created a briefing for myself on SimBrief for this flight and the briefing just said climbing or descending for the waypoints without saying anything about where the pilot should be in that process.  Later, I did the same thing for a flight plan from EGPH to EGKK and looked at the chart for the STAR and the vertical profile in the briefing, and the profile from SimBrief had the plane WAAY above what the charts said were the expected altitude at the first two waypoints of the STAR.

In the absence of ATC it looks like the pilot that relies on SimBrief flight briefings, without looking closely at the charts as well, is going to be missing some interesting parts of the flight?

Just trying to educate myself better on flight plans from both the pilot and ATC standpoints.  I probably should learn about how they are entered into their on-board computers and what it takes to change them.

 

Edited by Janet Kino
grammar
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Simon Kelsey

Hi Janet,

A level change on a flight plan indicates the point at which a change of level is planned to commence.

That said what I would say here is that to some extent this is academic because what goes in the flight plan may not necessarily be what happens in practice on the day. Looking at some previous real-world plans between Edinburgh and Berlin I can see both “versions”, one with planned as Trevor suggests at FL390 and another planned as in your example with a descent to FL230 at DLE.

One possible guess at why this might be is that it is possible the latter may have been planned as a such time avoid a slot restriction which may have been in place had the higher level been planned (the Eurocontrol flow management system looks at the expected traffic throughout and given that obviously most traffic would ideally want to be cruising in the mid-300s it is possible that a high-level sector in that area may be (expected to be) overloaded and so to mitigate this aircraft filing flight plans through that sector will be issued delays. Planning the flight at a lower level may get the aircraft out of the affected sector and therefore eliminate the slot.

In practice, depending on the actual situation at that moment, it is possible or even likely that the aircraft may remain at the higher and more fuel efficient initial level if the actual traffic levels in the affected sector at the time allow, so to some extent it can be a paper exercise…

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Janet Kino

Fantastic Simon!  From my standpoint it is only, and will only be, a paper exercise, and in any case, I am very unlikely to ever be controlling traffic flying in that area.  But what we are talking about here does help me understand what might be going on in someone's head when I am looking at a more complex flight plan in the future. 

Where do you find real world flight plans to look at?  I had to throw my hands up in despair at a EGPH to OMDB one last night.

 

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Trevor Hannant

SimBrief is usually fairly good although sometimes, if there's no Eurocontrol validated route to fall back on, it will throw back simply what someone else filed whether it's decent or not.

Take a look at https://edi-gla.co.uk/ also, even if there's no route between the two (which there isn't in this case), you can use something else close by to get the essentials then tweak - for example, there's a Glasgow to Dubai service which you can start as your base plan and tweak as required.

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