hazek wrote:
Ok, so how do you interpret this then?
The passage you quote is about altimeter setting procedures. I don’t think we are in any disagreement here. We are also not in disagreement that aircraft levels are never expressed as flight levels in cruise flight at or below the transition altitude.
But that is not the question. The question is how a lower limit of airspace is to be interpreted when it is given as a flight level which can not be used to express a level in cruise flight. That is a different question. I agree that your interpretation makes sense but that doesn’t mean it is what the UK CAA intended.
@hazek, this is the SERA definition of “flight level”:
flight level (FL) means a surface of constant atmospheric pressure which is related to a specific pressure datum, 1013,2 hectopascals (hPa), and is separated from other such surfaces by specific pressure intervals;
You may note that it makes no reference whatsoever to the transition altitude. By the way, ICAO Annex 2 has the identical definition.
Airborne_Again wrote:
The passage you quote is about altimeter setting procedures.
Yes, exactly. Because these procedures ARE how aircraft flying level is determined! And you claimed I had my own interpretation for. So I take it that you now say that I do not and that in fact at or below the TA the position of the aircraft is supposed to be expressed as altitude in reference to the correct QNH?
If that is the case, please tell me, how can following this published procedure, setting the correct altimeter setting and having a reading on my altimeter at or below the TA, how can that possibly put you within FLs and thereby busting a FL lower limit of a CAS?
If that is not the case, please cite the procedures that must be followed in order to determine the aircraft correct vertical position.
Btw I don’t know why you keep bringing up the lower limit of the CAS. That obviously never changes. But the CAS doesn’t fly into us, we fly into it. It’s our position that determines whether or not we are inside or outside CAS. And our position is determined by following the altimeter procedures.
hazek wrote:
And our position is determined by following the altimeter procedures.
No. The aircraft’s position does not depend on any “procedure”. You don’t have a different position depending on how you determine it, you may just have the same position expressed in different frames of reference or with respect to different datums. This is basic stuff…
hazek wrote:
following this published procedure, setting the correct altimeter setting and having a reading on my altimeter at or below the TA, how can that possibly put you within FLs and thereby busting a FL lower limit of a CAS?
Following a procedure does not “put you in” the flight levels. You can ALWAYS express an aircraft’s vertical position as a flight level independently of what the TA/TL are.
We use the TA/TL to inform which frame of reference we use, as a convention, but it doesn’t mean the other reference magically “disappears”.
It’s pointless, he’s not getting it…
Alpha_Floor wrote:
We use the TA/TL to inform which frame of reference we use, as a convention
As a convention?
This is now bordering on trolling now.
2 INTRODUCTION
2.1 The Altimeter Setting Procedures in use in the UK generally conform to those contained in ICAO Doc 8168-PANS OPS/611 and Doc 4444-PANS ATM/501. Differences are in bold.
2.2 The purpose of these procedures is to provide pilots with suitable pressure information which will assist them in maintaining adequate terrain clearance and also to ensure a safe standard of flight separation by the general use of altimeters set at 1013.2 hPa.
From ICAO Doc 8168:
Chapter 1
INTRODUCTION TO ALTIMETER SETTING PROCEDURES
1.1 These procedures describe the method for providing adequate vertical separation between aircraft and for providing adequate terrain clearance during all phases of a flight. This method is based on the following basic principles:
a) States may specify a fixed altitude known as the transition altitude. In flight, when an aircraft is at or below the transition altitude, its vertical position is expressed in terms of altitude, which is determined from an altimeter set to sea level pressure (QNH).
b) In flight above the transition altitude, the vertical position of an aircraft is expressed in terms of flight levels, which are surfaces of constant atmospheric pressure based on an altimeter setting of 1 013.2 hPa.
c) The change in reference from altitude to flight levels, and vice versa, is made:
1) at the transition altitude, when climbing; and
2) at the transition level, when descending.
d) The transition level may be nearly coincident with the transition altitude to maximize the number of flight levels available. Alternatively, the transition level may be located 300 m (or 1 000 ft) above the transition altitude to permit the transition altitude and the transition level to be used concurrently in cruising flight, with vertical separation ensured. The airspace between the transition level and the transition altitude is called the transition layer.
e) Where no transition altitude has been established for the area, aircraft in the en-route phase shall be flown at a flight level.
From PANS-ATM ICAO Doc 4444:
4.10 ALTIMETER SETTING PROCEDURES
4.10.1 Expression of vertical position of aircraft
4.10.1.1 For flights in the vicinity of aerodromes and within terminal control areas the vertical position of aircraft shall, except as provided for in 4.10.1.2, be expressed in terms of altitudes at or below the transition altitude and in terms of flight levels at or above the transition level. While passing through the transition layer, vertical position shall be expressed in terms of flight levels when climbing and in terms of altitudes when descending.
These are iron fking clad rules that you as a PIC are supposed to follow to ensure terrain clearance and aircraft separation. These rules are there for your own and the safety of the rest of us! This is not a matter of preference or theoretical discussion or merely a convention, it’s a matter of life and death.
Let me put it differently. If you don’t follow these rules you are not only not abiding by the current regulations and deserve your license to be suspended, you are also being grossly negligent, irresponsible and dangerous.
And you cannot bust a FL boundry if you are at or below the TA, period. Mic drop, I’m out.
hazek wrote:
I don’t know why you keep bringing up the lower limit of the CAS.
Because that’s what this whole discussion is about!
@hazek wrote:
Mic drop, I’m out.
You know, if you from the outset had said that a reasonable interpretation of the lower limit of a CTA being expressed as a flight level is that it can never be lower than the transition altitude, then this discussion would have been very different. Instead you went off arguing about altimeter setting procedures which no one here have disagreed with.
hazek wrote:
arj1 wrote: AIP are mostly not rules – they are just “publications”, for information.https://skybrary.aero/articles/aeronautical-information-publications-aips
I mean you I can also go quote Annex 15 if you really want but you can read the relevant summary at the above link. The AIP is THE publication pilots are supposed to read in order to know how to abide by the air regulations of a given country. If you the AIP is just guidance for information for you, where do you read the air regulations from so that you know you abide by them?
“The AIP contains details of regulations, procedures and other information pertinent to the operation of aircraft in the particular country to which it relates. It is usually issued by or on behalf of the respective civil aviation administration and constitutes the basic information source for permanent information and long duration temporary changes.”
@hazek, the regulations themselves are in SERA, PART-OPS (PART-NCO in my case), Air Navigation Order etc. I have e-mails from CAA regarding some parts of AIP stating that those are outdated.
So as many pointed out, you could determine your position vertically in many ways.
It could be QFE for the military airfield that owns the airfield, or INFO that provides service in Class G above that airfield or CONTROL that owns airspace above that Class G, and starts at, for example, FL55, and you could have your vertical position specified on three different ALT settings at the same time, just as Alpha_Floor was saying.
Then you fly well below FL55, ask for a flight plan to be activated, you are given a clearance to enter CAS in a climb to FL90, for example, advising you that a TA is 6000 and FL85 is a TL; you change from QNH to STD at that moment as you climb and you’ve climbed to FL90. At that moment you could determine your vertical position on QNH or on STD, yes, I know that this particular ATCO will expect you to operate in FL, but you might still choose keep one of altimeters on QNH, for obstacle clearance reasons, for example, or so you don’t breach some other CAS in descent.
So you see, you can measure your vertical position any way you like and different ATCOs and ATSUs will expect you to determine your vertical distance to obstacles and CAS in units specified in the charts, be that FL, AMSL, etc. Even if you are below a TA predominant in the area (6000 in case of Solent), they still expect you do be below FL55 on STD altimeter setting AND above MSA (if you are flying IFR) on QNH at the same time. I presume it is done to provide the CAT flying LOW on flight level inside that CAS with sufficient vertical clearance. I would like them to have two CASes one on top of another to have adjacent vertical borders to be specified in the same units (like it is done most other places in the UK and outside the UK as well), but they’ve messed it up that way, presumably, because both pieces of CAS owned by two different organisations.
I think he’s an ATCO and I don’t think he’s done any flying.
You can set your altimeter to whatever you damn well please. Outside of CAS nobody is going to know or care. But if you report it to some ATSU then you’d better set it to some reference that means something to them, and if you fly near CAS then it’d be a good idea to set it to whatever the CAS uses, be that 1013 for FLs or local QNH.
For the record, I have no idea how to establish TL/TA at any given point in the ludicrously complex UK environment. My work around is that I use altitudes unless (a) FLs become relevant due to proximity of CAS with the base defined as an FL, or (b) an ATCO to whom I’m reporting my level makes it clear that we’re high enough to be dealing in FLs. Mental altimetry arithmetic in the cockpit is not something I do.
