SkyDemon Forums

Switzerland: Airspace C Warning for Flight Level 130

http://forums.skydemon.aero/Topic26421.aspx

By Tim Dawson - 7/9/2018 8:41:47 AM

Are you saying you have obtained a clearance to fly at exactly FL130, on the border between two airspace classes? Who issued that clearance?
By airborne - 7/9/2018 8:54:35 AM

 
Tim Dawson - 7/9/2018 8:41:47 AM
Are you saying you have obtained a clearance to fly at exactly FL130, on the border between two airspace classes? Who issued that clearance?

No, a clearance is not necessary for flying in airspace E, in this case up to (and including) FL 130. There is also no 'between', FL 130 is part of airspace E because it is the lower airspace class.
By Tim Dawson - 7/10/2018 10:21:53 AM

If you were flying at FL130, at least part of your aircraft was in class C airspace. Of course SkyDemon warns you if you're flying (or attempting to fly) along an exact border of airspace, whether vertical or lateral. I don't see the problem here and I don't think we'll be adjusting the software's behaviour.
By airborne - 7/10/2018 11:08:43 AM

 
Tim Dawson - 7/10/2018 10:21:53 AM
If you were flying at FL130, at least part of your aircraft was in class C airspace. Of course SkyDemon warns you if you're flying (or attempting to fly) along an exact border of airspace, whether vertical or lateral. I don't see the problem here and I don't think we'll be adjusting the software's behaviour.

That is not how airspace limits according to ICAO work. Flying at FL 130 in the given situation is flying in airspace E, you do not need a clearance for parts the aircraft in question … (I hope that was some kind of British joke and not your serious opinion.) From an ATC perspective, you are in controlled airspace E and not in airspace C. You do not need a clearance as long as you remain on FL 130 within the defined tolerances.

Your warning is incorrect since the journey does not pass through general airspace C ('General Class C' in your words). If you consider a warning necessary, it could be worded something like 'Your journey passes right below General Class C'.

Please check ICAO Annex 11 for further information. You will for example find the following note:

'Where the ATS airspaces adjoin vertically, i.e. one above the other, flights at a common level would comply with requirements of, and be given services applicable to, the less restrictive class of airspace. In applying these criteria, Class B airspace is therefore considered less restrictive than Class A airspace; Class C airspace less restrictive than Class B airspace, etc.'
By airborne - 7/10/2018 11:14:53 AM

PS: The safety margin is 300 feet. (It would be 200 ft for RVSM.)
By Tim Dawson - 7/11/2018 11:16:09 AM

I'm afraid we will need to remain in disagreement over this particular issue.
By airborne - 7/7/2018 1:10:38 PM

For flights on flight level 130 over the Alps in Switzerland, SD issues the following warning:

Your journey passes through General Class C

The warning is incorrect. Flight level 130 is the border between airspace E und C, and as a result, flight level 130 belongs to the lower airspace class, i.e., airspace E. That is ICAO's standard (although it might be different in some countries).

(With MIL OFF, the issue concerns flight level 150. And the issue probably exists with other similar airspace limits too, for example for flight level 100 north of the Alps in Switzerland.)