hazek wrote:
hen by definition you can’t be at FL55. So how can you possibly bust a level that you aren’t at?
Please explain how a lower airspace limit of FL55 is to be interpreted when the transition level is higher than than (or even when FL55 is inside the transition layer).
@Airborne_Again: I know you know the answer but my take is it’s at the level your altimeter reads when it says 5500 and is set to 1013hPa.
I’m now curious to overfly SAM at 5600/1013 on a high pressure day where where should be a nice gap between the D up to 5500 and the A from FL55 :-)
I though from discussions here that you’ll be busted being 1 ft into CAS… We’ve gone through this again and again and I’ve been led to understand that the CAA does not take altimeter error, mode C resolution or QNH roundoff into consideration? With 200 ft margin being applied, I don’t see what the problem is! Anyway…
Yes the CAA will bust you but they have no evidence if it is 1ft. The ATC units have a local barometer which feeds into their system and displays the target altitude (as e.g. A2100 for 2100ft altitude – there are ATCOs here buit they almost never participate in these threads, and it could be just “A21” i.e. nearest 100ft) and if it says A2600 then the ATCO must do an MOR. What I think however (and I have no evidence) is that if the pilot presents GPS data showing 1999ft, the CAA guy may well not bother, because some GA pilots do have good lawyers, and then NATS will need to spend money producing equipment calibration certificates etc. Of course in the meantime the CAA has permanently (“provisionally”) suspended your license, because there is NO other way to have your case heard in a court.
Att 2000 ft, you’d need an air temperature of about -15°C, corresponding to a sea level temperature of about -11°C at standard lapse rate to get a 200 ft error.
That would be quite rare. The UK rarely gets colder than -5C.
Please explain how a lower airspace limit of FL55 is to be interpreted when the transition level is higher than than (or even when FL55 is inside the transition layer).
I am not sure the TA has any relevance whatsoever in real life. The sole reference is the VFR chart. If it says 5500ft then you set the owning unit QNH. If it says FL055 then you set 1013. How you get from one to the other is not the CAA’s problem.
Teaching the diff between GPS alt and baro alt is not in the PPL, IME. Most UK pilots use SD to hold their hand everywhere… But most CAS busts are not due to these kinds of errors; they are caused by brief distractions.
Wrong. Any flight can always be refused and must have a plan B. In fact this is a question in the question bank for ATPL:
Hazek – you should apply for a job at a frozen ATPL CPL/IR/ME flying school 
Of course every country owns its airspace. But that is a completely disingenuous point. One day if/when you get an IR and a plane to use with it, you will know what I mean.
Peter wrote:
I am not sure the TA has any relevance whatsoever in real life. The sole reference is the VFR chart. If it says 5500ft then you set the owning unit QNH. If it says FL055 then you set 1013. How you get from one to the other is not the CAA’s problem.
In agree with you, but Hazek seems to be of a different opinion. His posts seem to imply that you can’t bust airspace with a flight level as lower limit as long as you fly below the lowest useable flight level, which is determined by the TA and QNH. That doesn’t make sense to me – thus my question.
I don’t understand that either. AIUI, the TA is merely the level (if you are given an “unrestricted climb”, say SFC to FL150 on departure) at which you change the altimeter from QNH to 1013, or vice versa if descending.
And many pilots don’t really operate that anyway e.g. I would set 1013 in such a climb more or less ASAP (because forgetting will cause a level bust) and similarly when descending (especially in IMC and especially if flying an IAP).
The gotcha is obviously when e.g. descending, if you stay on 1013, you can easily bust CAS if heading into this kind of airspace
but that is just an argument for setting QNH ASAP and not around the TA (or TL).
Guys, this is really basic, do you really not understand how your aircraft’s vertical position is established correctly? Do you know that not knowing this can get you killed? I mean forget about rules and infringing a CAS, you could literally die if you don’t understand and apply what is listed here:
I mean c’mon. Do better. You owe it yourselves.
This is a windup, surely.
hazek wrote:
I mean c’mon. Do better. You owe it yourselves.
We do better. Now make the CAA do better?
If you are below TA but above the CAS bottom that is defined as FL – you have infringed.
Welcome to out world.
hazek wrote:
Guys, this is really basic, do you really not understand how your aircraft’s vertical position is established correctly?
I understand that very well, but you are not evading the question. If the lower limit of a control area is defined as a flight level, and the QNH is low enough so that flight level is below the TA, then what is the highest you can fly without infringing?
(And I know very well that cruising levels are determined using QNH below the TA, but flight levels still make sense as pressure surfaces.)
None of this is relevant to getting busted for busting CAS. You simply need to be below the area shown on the VFR chart – either using QNH or using 1013. All the stuff about TA or TL is immaterial.
BTW, my vague recollection from many years ago was that when climbing you change to 1013 at the TL, and then descending to change to QNH at the TA. But I don’t recall ATC ever passing the TL figure; only the TA, and that only in a few places (Croatia comes to mind). Anyway I don’t know anybody who actually flies IFR (at reasonable altitudes like FL150) and who use TA or TL for the altimeter resetting point.
