Query on UK flying above 3000ft

[dublinpilot]

Guys,

I just wanted to check two things about flying in the UK with you.

1. Am I correct in saying that flying about 3,000 (or transition altitude if CAS) should be by reference to Flight levels rather than altitudes?

2. I understand that crusing above 3000 is by reference to the quadrangle rule. Is this compulsary or recommonded?

This is particularly relavant for cross water crossings, where I'd like to get as much altitude as possible, which could obviously be quite a bit lower if quadrangle is compulsory.

Thanks for the info.

dp

[Pianorak]

Operations within CAS – Above 3,000 ft amsl, or above the appropriate transition altitude, whichever is the higher, en route aircraft are flown at flight levels (ie with standard pressure 1013 mb set) to assist in separation from other traffic.

In level flight above 3,000 ft amsl pilots flying under the IFR must have 1013 mb set and conform to the quadrantal rule when selecting cruising levels. Vertical position will then be expressed as a flight level.

VFR traffic above 3,000 ft amsl may operate on Regional QNH; however, en route flights choosing to fly quadrantal levels must have 1013 mb set. The quadrantal rule is a means of vertically separating traffic flying in different directions. Whilst it is required for IFR traffic below FL245, it is strongly suggested for VFR flights as well.

(Courtesy of Trevor Thom)

Hope this helps.

[IO540]

There seem to be frequent exceptions to this. For example the ATC for a Class D zone (which you entered flying "IFR" on some flight level) can tell you to fly at a specified altitude which would be on QNH, or would be on QFE if it is a military airfield - all despite one being "IFR".

[Charlie Zulu]

The Transition Altitude is 3000' unless otherwise specified.

For example, Cardiff has a transition altitude of 4000'. The transition altitude can be found in the AIP.

[bookworm]

Outside controlled airspace:

* IFR flights must select quadrantal levels when flying above 3000 ft or the transition altitude (whichever higher).

* VFR flights are advised to select quadrantal levels when flying above 3000 ft or the transition altitude (whichever higher).

Inside controlled airspace:

* IFR flights fly at the level assigned by ATC

* VFR flights fly at whatever level they please, subject to any restrictions in their clearance.

The transition altitude does not affect only controlled airspace. If you are flying IFR below a TMA within the horizontal extent of which the transition altitude is higher than 3000 ft, you are not obliged to fly quadrantal levels. It's rarely important in practice, but does come in handy from time to time.

Maximizing altitude for a water crossing under VFR seems like a good reason for selecting a non-quadrantal level.

[dublinpilot]

Thanks guys. Much apreciated.

dp

[italianjon]

I know this is ressurecting this thread, I am trying to find out a bit of info...

I was under the same impression as the thread, that VFR are not required to comply with the Quad rule above the TA. However apart from Trevor Thom, which to be fair (No disrespect it's a great book) it is the author's opinion, where is it written that VFR are advised to follow the Quad rule?

This question has come up at work and none of us can find it either in the ANO or AIP...

[FlyingForFun]

Italianjohn,

Try the AIP, section ENR 1.7 - Altimeter Setting Procedures. (You will need to register and sign in to access this.) Paragraph 5.2.2.2 (at the bottom of page 2 of the PDF) states:

5.2.2.2 When flying under IFR above the Transition Altitude pilots must have 1013.2 mb set on an altimeter and conform to the Quadrantal Rule in accordance with ENR 1-7-4, paragraph 6.1 when flying at/below FL 245, and the Semi-circular Rule when above FL 250. When flying under VFR pilots are recommended to conform to the Quadrantal Rule and Semi-circular Rule as appropriate. The latest and most appropriate lowest forecast Regional Pressure Setting value should be used for checking terrain clearance.

FFF
--------------

[cadaha]

I believe that it also states that 3000 - 3500 is a transistion layer and it is recommended that that layer is purely for transistion to ensure that any differences between QNH and 1013 ensure that there is adequate seperation between A/C and shouldn't be used as a FL. Once you set 1013 and through the transition layer assume FL based on quadrantal rules. If I read TT correctly.

[FlyingForFun]

Cadaha,

The transition layer is the space between the transition altitude and the first available flight level.

For example, assume that the transition altitude is 3000', and the QNH is 979mb.

The QNH is 34mb below standard pressure. So, assuming 30'/mb, if you climb to 3000' and then set your altimeter to 1013, you will add 1020' to your indicated altitude - you will now be indicating 4020'.

The first flight level must be higher than the transition altitude. So, if the transition altitude is 3000' QNH, and that equates to FL40.2, then FL30, FL35 and FL40 are all unavailable. The first useable flight level will be FL45, and the transition layer will be the space between 3000' and FL45 (a total, in this case, of 480').

Hope that makes sense.

FFF
----------------

[Whopity]

The Transition Layer is there as a buffer to ensure that:

a. When climbing, the first useable flight level is not below the Transition Altitude

b. That when descending the Transition Level is above the Transition Altitude.

It will only be 500 feet when the QNH is 1013.2.

If you are flying VFR on the RPS or QNH the transition Layer, Level or Altitude are not relevant.

[cadaha]

Thanks for the amendments to my understanding guys, getting clearer now.

One quick question FFF wouldn't the first available FL be FL050 to ensure that a minimum seperation of 500' exsists because as you said that 3000' @ regional QNH = 4020' @ 1013 (indicated) which only gives 480' @ FL045 or am I still missing something.

Thanks

[Spitoon]

There's been lots of discussion over the Transition Level where I work. Some hold the view that TL is the first FL (ending in 0 or 5) that you come to as you go up from TA - others think that it's the first FL that is separated from TA. The definition in UK books is ambiguous but I read somewhere recently that Eurocontrol has defined it more clearly as the latter.

[bookworm]

The definition in UK books is ambiguous but I read somewhere recently that Eurocontrol has defined it more clearly as the latter.

MATS Pt1 clearly defines it as the former. Feels like something that ICAO should resolve.

[IO540]

This is going to sounds terribly ignorant, but I never worried about this stuff.

VFR outside CAS, one can fly anywhere. The quad levels are UK only anyway, abroad one flies the semi levels, and if flying an ATC directed level or route (rare in the UK but not rare abroad) then one flies the appropriate flight level, and usually the higher the better.

VFR in CAS, one does what one is told. ATC don't seem to care about this, and assign you any level that suits them, even if it is completely "against the rules".

IFR outside CAS, UK, one can fly anywhere but one tries to fly the correct levels.

IFR in CAS one does what one is told.

Interesting about the transition layer. Never knew about this!

[cadaha]

Excellent thread this! Really makes you think about possible traffic conflict.

So my undertsanding now is that even if you are VFR and intend flying above 3000' then you should adopt altimeter setting of 1013mb and follow the quadrantal rules based on that setting and the track that you are flying as this would ensure minimum of 500' seperation between you and other traffic flying on different tracks which are liable to conflict with you.

Sounds reasonable.

Once descending below transition layer either select Regional QNH or Aerodrome QNH (if descending direct to airfield)

Need to keep a bloody good look out for conflicting traffic whatever level you are flying at as some people don't adhere to these rules (more like advise rather than rules to me) as VFR flights are not required to follow these rules (Mmmmm).

Also it seems that as you descend you would probably have an idea where to look for traffic as you would know where the IFR traffic is likely to be coming from during your descent although there could be VFR traffic coming from any direction (Jeeze!!).

Once through the transition layer traffic could be coming from anywhere.

Broad brush but is that the basics then????

By the way the above assumes outside CAS otherwise do as you're told.

[140cherokee]

Don't forget that if you're above 3000' and less than 1000' from cloudbase, you are not VFR and should fly quadrantals.

140

[unfazed]

VFR in CAS, one does what one is told. ATC don't seem to care about this, and assign you any level that suits them, even if it is completely "against the rules".

IO540 - What you say is correct but you should challenge ATC if they assign you a level that is against the rules. They may well be setting you up for a very unpleasant experience. Don't forget that ATC have been known to give clearances to proceed direct and descent to levels that are below mountain heights !! (talking worldwide ATC here)

[IO540]

"Need to keep a bloody good look out for conflicting traffic whatever level you are flying at as some people don't adhere to these rules "

From what I've come across in my mere 550hrs, there is a far bigger problem with people not knowing that in a head-on situation they should turn RIGHT, than with people flying the wrong quad levels.

In any case, abroad one doesn't fly the quad levels anyway, so this whole subject is partially moot. I think one can develop a statistical case for this type of traffic separation (flying different levels according to the track) but I've never seen the percentages. IMV the safety benefit is relatively small.

"you should challenge ATC if they assign you a level that is against the rules. They may well be setting you up for a very unpleasant experience. Don't forget that ATC have been known to give clearances to proceed direct and descent to levels that are below mountain heights !! (talking worldwide ATC here)"

In theory, the pilot remains responsible for terrain clearance, and I don't see why flying quad (or semi, outside the UK) levels affects this. The terrain doesn't care if you are flying the correct level. All that matters, for terrain clearance, is the local QNH viewed versus the chart. Even blindly using the altitude derived from a GPS is a whole lot safer than trying to mentally convert a flight level to an altitude, using the difference between QNH and 1013.

Other than terrain, I will accept whatever level ATC give me; they have the radar or procedural picture, I haven't.

"Don't forget that if you're above 3000' and less than 1000' from cloudbase, you are not VFR and should fly quadrantals"

Again, quads are a UK-only peculiarity. This rule, of all, is one which people worry about least, especially if under radar control. You just "maintain VMC".

[Chilli Monster]

IO540 - What you say is correct but you should challenge ATC if they assign you a level that is against the rules.

Aircraft under the control of an ATC unit, flying a level allocated by that unit, are exempt from complying with quadrantal / semi-circular rules. (MATS Pt. 1 / ANO)

I do agree with the comment about flying a level below MSA - no self respecting ATC unit would (I hope) do that. However, do bear in mind that a level when being vectored, although being below MSA, will still be terrain safe as that area has been more thoroughly surveyed.