When to change to 1013mb?

[Hoover Pilot]

Following discussion with a colleague I would like to hear ATC's opinion please.

In the London area the transition is 6,000ft. My old airline’s SOP was to change to 1013mb as soon as we are cleared to a FL. However my current SOP (different airline) is to change to 1013mb at transition altitude and not before.

The uk rules (notified difference from ICAO) say (from memory) that when cleared to a FL all references to height shall be expressed with reference to 1013mb. Thus indicating that the change to 1013mb shall be carried as soon as one is cleared to a FL. But does it actually mean that…or does it just mean if the passing height has to be passed to ATC then it should be given as a FL.

The tricky thing would be to have to stop the climb after having changed to 1013mb. Would ATC instruct me to stop the climb at an altitude or a flight level? (bearing in mind, in this case, I am still below the transition altitude)

Cheers HP

[Jumbo Driver]

HP, I realise you are asking for a reply from the ATC perspective but surely the UK AIP (ENR 1.7 (http://www.nats-uk.ead-it.com/aip/current/enr/EG_ENR_1_7_en.pdf)) is quite clear on this?


ENR 1.7 — ALTIMETER SETTING PROCEDURES

5 Detailed Procedures

5.1 Take-off and climb

5.1.4 Within Controlled Airspace a pilot should set one altimeter to the latest Aerodrome QNH prior to take-off. While flying at, or below, the Transition Altitude vertical position will be expressed in terms of altitude based upon the Aerodrome QNH. When cleared for climb to a Flight Level, vertical position will be expressed in terms of Flight Level, unless intermediate altitude reports have been specifically requested by Air Traffic Control.

5.1.5 Outside Controlled Airspace, a pilot may use any desired setting for take-off and climb. However, when under IFR, vertical position must be expressed in terms of Flight Level on climbing through the Transition Altitude.5.3 Approach and Landing

5.3.1 When an aircraft is descended from a Flight Level to an Altitude preparatory to commencing approach for landing, ATC will pass the appropriate aerodrome QNH. On vacating the Flight Level, the pilot will change to the aerodrome QNH unless further Flight Level vacating reports have been requested by ATC, in which case, the aerodrome QNH will be set following the final Flight Level vacating report. Thereafter, the pilot will continue to fly on the aerodrome QNH until established on final approach. When requested by the pilot or local procedures require, the appropriate QFE and aerodrome or threshold elevation shall also be given.


In any event, you will/should always have a second or stand-by altimeter set to QNH during the climb and descent so that you can reference any request to altitude, if 1013 is already (or remains) set.


JD
:)

[yakkity yak]

HP and jumbo driver,

from an ATC perspective and having worked in north america, australia, middle east and kiwi the UK procedures are quite frankly dangerous and at odds with the way I have done it in other jurisdictions. The saving grace in the UK is that the transition altitute is only around 6000 feet so most jets are through that in a few minutes. however in the US and Canada the transition altitude is 18,000 feet (or thereabouts) in the ME it is about 12,000 feet or so and in Australia it is 10,000 ft.

In these places I have worked, the controllers concerned are expecting the aircraft to set standard pressure (1013) passing the transition altitude as if they are watching your altitude readout to confirm you have passed a specific altitude (at or below the transition altitude) they will be expecting your altitude readout is referenced to the local/area QNH. remember the controller requires your mode C readout to be +/- 400ft or more above/below (with the aircraft descending or climbing in the correct direction) the altitude/level that is required to achieve separation.

eg lets say the local/area QNH is 1000hp, and you are in Australia where the transition level is 10,000ft. The controller does not have an urgent separation problem but does need to see you out of 9,000 ft due to distant crossing traffic at 8,000. If it is really urgent he could give you an altitude requirement to cross 9,000 by a point/time or distance...would you still set 1013, I should hope not as this is an altitude requirement you should be on QNH. if it is not so urgent then the they may say report leaving 9,000 or if they have assessed your rate of climb after a few sweeps of the radar and ascertained you are climbing well they will watch to see your mode C readout pass 9,400 (and showing your climbing). In all cases you need to be on area/local QNH because with this pressure differential you could be 400 ft lower than you really are if you have already set 1013 when cleared to a FL... and suddenly there is an incident because of sloppy application of altimitery procdures.

Also, remember that there could be other aircraft in the vicinity cruising at altitudes and this could affect the integrity of TCAS if your mode C is using 1013 instead of QNH.

HP your new airline has got it right, the old airline SOP's and the UK procedure is an horses arse, and should be rectified.

hope this helps

[Jumbo Driver]

yakkity yak, I fully accept that altimeter setting procedures in North America and elsewhere are different.

However, HP's question related to UK airspace and that is why I answered in that context.

Incidentally, Mode C is always referenced to 1013, irrespective of any altimeter setting.


JD
:)

[ATCO1962]

Does the UK not have a transition level as well as a transition altitude, defining the layer between which no aircraft should maintain level flight, so as to ensure separation between those aircraft flying at flight levels and those on local QNH?

Many moons ago, we were taught that a/c climbing change to 1013 as they passed through the T/A and those descending changed to local QNH on passing T/L. Has that changed and noone told me??

[BOAC]

In the UK, most certainly, as you can read in JD's post above.

[BOAC]

Hey! Hoover Pilot - what is that 3 down in the list at the bottom?:ugh:

Not a slow learner, I hope.........................:)

[anotherthing]

The UK does have a Transition Layer, aircraft can fly in it if they wish (obviously OUTCAS).

The TL is used primarily to ensure a minimum separation requirement exists between the TA and the Minimum (Useable) Flight Level. i.e. the TL is merely a step in the calculation.

[Jumbo Driver]

The TL is used primarily to ensure a minimum separation requirement exists between the TA and the Minimum (Useable) Flight Level.

I don't think you are quite correct here, anotherthing.

ENR 1.7 (http://www.nats-uk.ead-it.com/aip/current/enr/EG_ENR_1_7_en.pdf) says, in this connection, at 3.3 (my bold):

3 General Procedures

3.3 The vertical position of aircraft at, or below, any Transition Altitude will normally be expressed in terms of Altitude. The vertical position at, or above, any Transition Level will normally be expressed in terms of Flight Level. When descending through the Transition Layer the vertical position will be expressed in terms of Altitude, and when climbing in terms of Flight Level. It should not be assumed that separation exists between the Transition Altitude and the Transition Level.


JD
:)

[Hoover Pilot]

People – thanks for the replies. I should say that this came from a discussion over a drink and is not a question how to operate – the SOPs tell me that and I follow them.

Jumbo – thanks for posting the correct text my recollection was basically correct in that it says “vertical position will be expressed in terms of flight level” after being cleared to a flight level. However I find your comment:

“in any event, you will/should always have a second or stand-by altimeter set to QNH during the climb and descent so that you can reference any request to altitude, if 1013 is already (or remains) set.”

a little bit arrogant because you do not know what my SOPs say. Basically in the type I fly we have 2 main altimeters and 1 standby. The standby is ALWAYS set to 1013mb and the mains adjusted as we climb in accordance with SOPs (both mains are always sets the same).

So if we were to go to 1013mb when cleared to a flight level then we would have no altimeter set to QNH should ATC wish to stop our climb at an altitude. By keeping the main altimeters on QNH we can “express our vertical position in terms of FL” by reading off the standby AND stop the climb at any altitude as required.

A colleague of mine (in another airline) started this discussion by stating that once we were cleared to a flight level then ATC will expect all vertical positions to be referenced in flight levels – including any subsequent “stop climb” instructions – even if below the transition altitude. Hence this posting for the opinion of ATC from the UK and preferably in the London TMA as this has the 6,000ft transition.

Cheers HP

Ps BOAC sorry I’ve no idea what you are referring to with “3 down”. If that means “slow learner” then guilty as charged.:)

[Jat Jet]

when climbing change to 1013 at Tranisional Altitude and when descending change to QNH at Tranisitional Level:)

[Jumbo Driver]

Ps BOAC sorry I’ve no idea what you are referring to with “3 down”. If that means “slow learner” then guilty as charged.:)

Perhaps BOAC was referring to the fact that you started a thread (http://www.pprune.org/forums/showthread.php?t=130297)on exactly the same subject some time ago.

Best wishes ...


JD
:)

[Hoover Pilot]

Hi JD - yes quite correct, guilty as charged - a good topic for discussion.

What rekindled my interest in this discussion was my colleague's opinion that ATC after clearing me to a FL will expect all references to vertical position in terms of FL including any subsequent level off instructions even if below the transition altitude.

All opinions welcome also but only ATC can answer that one methinks...

HP

Ps Jat Jet – sorry have to differ, My SOPs are to go to QNH when cleared to an altitude in the descent.

[ferris]

JD
Incidentally, Mode C is always referenced to 1013, irrespective of any altimeter setting. Yakity's point was referring to the mode C readout ie. what is displayed to the radar controller (who has the RDP between him and the transponder output).

[Jumbo Driver]

Yes, HP, I agree it is a good topic for discussion but I am not sure we have uncovered anything new since the last thread, have we?

I still think the legislation at ENR 1.7 says it all. However, the concept of a Transition Layer between the TA and TL, where you have one reference in the climb and another in descent, has always been a thorny one. That is why it is generally not allocated as a cruising altitude/level, simply to try and avoid any ambiguities.

With regard to the stand-by altimeter, my apologies if you found my earlier comment "arrogant" - I didn't mean it to be so - but I do believe it is good practice to set QNH on it during the climb and descent. I am certainly not suggesting contravening your SOPs but, if it were me, I think I might be minded to suggest a relevant change in my Company SOPs, purely for the reasons we have discussed.

JD
:)

[Jumbo Driver]

JD
Yakity's point was referring to the mode C readout ie. what is displayed to the radar controller (who has the RDP between him and the transponder output).

ferris, I think we may be at cross-purposes - I was referring to his reference to TCAS, when he said:

Also, remember that there could be other aircraft in the vicinity cruising at altitudes and this could affect the integrity of TCAS if your mode C is using 1013 instead of QNH.


As I said, Mode C in the aircraft never uses QNH.



JD
:)

[anotherthing]

Ok JD,

I'll rephrase it so you understand what I was meaning, although my premise is correct.

TL is one step in the calculation (note the bold) that is used to work out the MSFL etc.

To quote my qoute, that you quoted(!!)
- The TL is used primarily to ensure a minimum separation requirement exists between the TA and the Minimum (Useable) Flight Level.

The TL may be less than 500' - hence the reference you quoted (with your bold).
What I was getting at when I typed that sentence was that to see if separation does actually exist between the TA and the T Level, you need to work out the T Layer. Hence, the T Layer is primarily (within the calculation) to ensure a minimum separation... etc etc. It doesn't really serve any other function.

If it separation doesn't naturally exist (highlighted when the T Layer is calculated) because the QNH does not differ dramatically enough from the SAS, then the MSFL is moved up accordingly. :ok:

[Jumbo Driver]

anotherthing, thank you - I think I understand your point ...

... now back to the topic (sorry HP) ...



JD
:)


PS my brain's beginning to hurt ... :confused:

[ferris]

JD, we are not at cross purposes: The checking of the transponder's integrity (Mode C) is going to be done by a call of the pilots altimeter reference the radar display, right? Hence the RDP conversion of the raw (1013) info. The pilot has no other way of checking what his transponder is outputting (it is invisible to him).

Yakity's point refers to this invisibility of what the transponder is outputting. The means of checking is invalidated if the pilot has the wrong setting dialled up (for the piece of airspace he is in). As well as the other problem he refers to.

[BOAC]

HP - glad we sorted that out!

Your 'colleague' is essentially correct What rekindled my interest in this discussion was my colleague's opinion that ATC after clearing me to a FL will expect all references to vertical position in terms of FL including any subsequent level off instructions even if below the transition altitude.
as JD has pointed out (and I am assuming you use the UK AIP since you have not said), to requote

"When cleared for climb to a Flight Level, vertical position will be expressed in terms of Flight Level, unless intermediate altitude reports have been specifically requested by Air Traffic Control."

as you yourself agreed in post #9 of your 'previous'.

Like JD I feel it vital to have the standby on QNH until TA at the earliest in the climb and at top of descent for SA. I personally would prefer regional QNH at all other times, but RVSM seems (unecessarily IMO) to have knocked that out of the equation. I also agree with JD that your SOPs would benefit from a revisit.

[Jumbo Driver]

ferris, I still believe we are at cross-purposes. yy said:

Also, remember that there could be other aircraft in the vicinity cruising at altitudes and this could affect the integrity of TCAS if your mode C is using 1013 instead of QNH.

This is quite clearly incorrect as TCAS cannot be affected by a wrongly set altimeter. TCAS uses Mode C (or Mode S) to assess the vertical position of the other aircraft. Thus there is no way that "the integrity of TCAS" can be affected if QNH is set on the altimeter, rather than Standard, i.e. 1013mb. That was what I was referring to ...

By the way, my transponder does give a visual indication of the Mode C data that is being transmitted (i.e. FL), so this data is not necessarily invisible to the pilot, as you say.

I am reluctant to prolong this thread creep, so if you think I am still missing your point, please PM me ...



JD
:)

[ferris]

A few things (and I think it's relevent);
1. The info dipslayed to you, and the info transmitted, are not neccessarily the same thing (have seen this several times).
2. The integrity of TCAS relies on the integrity of the transponder, and the manner of determining the intregrity of the transponder is reliant on correct altimeter setting. So, I disagree, and think that altimeter setting can affect TCAS.
Make sense?
3. If clearance instructions, hence separation, hence whether you will experience a TCAS event, rely on correct altimeter setting, then the two (three) are permanently tied.

[Jumbo Driver]

No, I'm afraid it doesn't make sense ferris.

Altimeter subscale setting cannot affect TCAS. It is irrelevant. Neither can it affect the Mode C response.

I respectfully suggest you re-read the theory of TCAS and Mode C encoding.


JD
:)

[ferris]

Altimeter subscale setting CAN affect TCAS. Not in the sense that adjusting the subscale directly does anything to either the TCAS unit or the transponder, but I'm sick of explaining myself over and over.

I respectfully suggest that you have a look at the relationships between radar displayed alt, radar data processing, and mode c, as described in this thread. The key point being that the RDP expects you to have the correct subscale setting.

[Jumbo Driver]

Thanks, Vercingetorix - I was beginning to lose the will to live there ... :ugh:

Perhaps we can now get back to the thread? Hoover Pilot has asked two questions; I hope ENR 1.7 has answered his first question. His second question was:

The tricky thing would be to have to stop the climb after having changed to 1013mb. Would ATC instruct me to stop the climb at an altitude or a flight level? (bearing in mind, in this case, I am still below the transition altitude)

As he seems to be talking about the London area, perhaps someone from TC may be able to enlighten him?


JD
:)

[ferris]

Hey JD, you had better watch whose support you receive. Vercingetorex is the clown who, after the Uberlingen accident, thought that it was correct for pilots to follow atc instructions over TCAS.

So, yeah, he's a TCAS expert. :cool:

As to the second part of your post- a question: What happens if the FMS is flying, and you are on a SID (which has altitude restrictions), but you are cleared to a FL and change the subscale? I take it the FMS is deriving it's data from the panel altimeters?

[Life's a Beech]

yakkity yak

I think you have answered your own point, in that your scenario couldn't happen where the transition levels are as low as they are in the UK, so UK procedures are appropriate here. However I think you have invented a problem that should not occur. As I was taught I change to SPS as soon as I was cleared to a flight level and have no need to use my primary altimeter for reference to altitude before reaching that flight level.

So if I was in a busy area, and asked to climb to say FL80, expediting through 5000 feet, then I would change to 1013 at 5000 feet. If all was quiet and I was on a steady track on autopilot, I might use the secondary altimeter (which I habitually leave on QNH until the cruise, as I was also taught) as the required altitude reference. Note that the worst that could happen in the UK by setting 1013 early is that I climb faster than I want to, or slower than ATC has requested I do, for a short time - no incident.

[ferris]

I gather that by posting those bulletins you are trying to say that you weren't aware that pilots were instructed to follow TCAS over ATC instructions, and that these were the first guidance on the matter.

At the time you made your statement of ignorance (July 2, 2002)- it was pointed out to you that that the instruction already existed in the AIP (where it had been the rule since the late 90's). Your response was "this country is a tin-pot little country with a rubbish AIP- proper countries dont have it". It was then pointed out that the "tin-pot country's" AIP was a cut and paste of the UK CAA document. To which you shuffled off to your office to check. Of no real consequence- except you were the SATCO at the time. Management by buffoon.

Yet another example of your shining brilliance. Said brilliance being the reason you were shown the door, no doubt.

[ferris]

and was not a cut and paste of the UK CAA Yes it was (or the relevent section was- as demonstrated to you at the time). Trying to be selective with the truth? How unusual for you! :=

Go on, tell us, why did you post those bulletins with dates highlighted, unless you are trying to say they are the first TCAS guidance? I dont think the wider audience is so easily fooled, and will recall when ACAS guidance was first about. It may be the trait of a manager to lie and deceive, but when the facts are in black and white, it's easy enough to see thru.

The fact that you were not aware that TCAS was/is to be followed above ATC instructions, despite the fact you were a "manager", remains. As I said, management by buffoon. Then again, lots of us in ATC know that.

[Jumbo Driver]

ferris, why don't you take your vitriolic personal attacks somewhere else? You are coming across as one who is obsessed with your own opinion, irrespective of the facts.

In case you have forgotten, this thread is about the setting of 1013mb when climbing throught TA and the Transition Layer.

If you think you have something useful to contribute to the topic, by all means do so - but good manners to the thread owner dictates it should be within the subject. Alternatively, you are free to start your own thread with the subject of your own choice (you could perhaps start with TCAS ... ). In any event, it is inconsiderate - and, in fact, rather boring - to take over someone else's thread with your own obsessive axe-grinding wanderings. It seems that your profile, at least, is pretty accurate.

Any chance of getting back to the topic?


JD
:)

[ferris]

I've tried to contribute, JD, but as my opinion differs to yours, clearly you dont like it. If someone has a different opinion, they are "obsessed with it"? I have tried to save you some embarrassment by identifying the depth of knowledge of the clown supporting you, but hey, you come across as an arrogant **** yourself, if you want to cast aspersions. Not only that, you haven't refuted a single thing I've said. I'd be looking in the mirror regarding obsessions and opinions.

I asked you a question (on topic) about altimeter setting and the FMS, which you have studiously ignored.

[Jumbo Driver]

Dear ferris, thank you for those kind considered words. I have printed them out and put it through my shredder - I feel so much better now ...

Yours ever,


JD
:)

[BOAC]

It looks as if ssg had a bigger family than we realised:ugh:

I guess HP pushed off long ago. Where is PPR when you need him?:)

[BOAC]

Good ol' Virgil:ok:

[Jumbo Driver]

non est ad astra mollis e terris via

... sed semper per altitudo transito ...


JD
;)

[Hoover Pilot]

Hi BOAC still here (though work beckons in a day or so) and have watched the demise (or drift) of this one. :ugh:

I was literally on the point of trying to bring it back the other day but JD beat me to it (thanks for that, by the way) but his efforts were in vain.

Seriously though thanks for all the responsible opinions but all I really wanted was the answer to one question. I do know what the regs say and have discussed my thoughts over my Company’s SOPs in this area, but their answer has been that if we are ever instructed to “stop climb” while we are still below the transition altitude then that instruction will be:
“stop climb altitude 4,000ft” and not
“stop climb FL50” – (or FL48 or FL52 or FL what-ever to maintain separation).

Therefore I was hoping for an answer from an ATC chap(ess) to the question:

“The tricky thing would be to have to stop the climb after having changed to 1013mb. Would ATC instruct me to stop the climb at an altitude or a flight level? (bearing in mind, in this case, I am still below the transition altitude)”

Here’s hoping……………….

Cheers HP

[Spitoon]

OK, here's an answer from a UK approach controller - i.e. TA/TL is day-to-day business. It's a personal view so you may get other answers from other posters!

I know what the UK rules are. I know that other States have different rules. I know that some SOPs do not adhere to UK rules whilst within UK airspace. I am aware that some pilots do their own thing regardless of the rules (and, sometimes, SOPs). In short, I am very aware of the issues involved - both for controllers and pilots.

Consequently, I will never clear an aircraft to climb to a FL knowing that I am going to want to stop the climb at an altitude. Frankly, if there's the possibility that I'll need to stop the climb because of other traffic then I'll only clear the aircraft to the safe level and then, as it approaches the level change, I decide whether I can clear it further. Same principles apply for descending traffic.

Some may say this is inefficient but it's fail-safe - and I've been in this game long enough to know how easy it is to get distracted.

But stuff happens and plans sometimes have to change. Working around the TA I'm always aware of the relationship between the TA and the next safe level. Therefore it is fairly easy to work out what level (be it a FL or altitude) will be safe relative to whatever the problem is if it really is necessary to change the plan. I'll use whatever level datum the pilot should be using according to UK rules first but if there's any hesitation or question I'll have the level referenced to the other datum ready. If it's all turning to a heap of manure there's always the 'stop climb now and advise the level' and I've got the mode C to help also.

In truth, particularly where the TA is 3000ft or 4000ft, it's not a common problem because it so rarely happens that a clearance needs to be changed whilst an aircraft is climbing through altitudes because it happens so quickly for most commercial ops type aircraft. Perhaps it's more frequent when descending but I haven't seen it done often. Of course, if TA is 10,000ft or 18,000ft it's going to be a different story.

[yakkity yak]

HP

I am an ATC enroute and approach controller and have worked in different worldwide jurisdictions. other than london where the TA is so low it barely matters, I would still expect PIC to have local/areaQNH set till passing TA on climb or passing TL on descent, especially in north america, australia, ME(for you intl pilots who fly there).

a late stop at an altitude on climb to FL's could happen at any time for any reason, so thus your co SOP's if memory serves me correctly are correct and QNH on the scale until TA. Tis also good airmanship as well as far as I am concerned .... and I also fly too.

hope that wraps it up!

cheers

[BOAC]

yy - from HP's post #10

Basically in the type I fly we have 2 main altimeters and 1 standby. The standby is ALWAYS set to 1013mb and the mains adjusted as we climb in accordance with SOPs (both mains are always sets the same).

So if we were to go to 1013mb when cleared to a flight level then we would have no altimeter set to QNH should ATC wish to stop our climb at an altitude. By keeping the main altimeters on QNH we can “express our vertical position in terms of FL” by reading off the standby AND stop the climb at any altitude as required.

....and thence the problem and why JD and I (at least) think his airline should review the SOPs.

Edit: Now we can add 'Max Angle'

[Max Angle]

Blimey, three pages and counting. I am great believer in KISS (keep it simple stupid) and fortunately my airlines SOP agrees. Set 1013 as soon as you are cleared to FL no matter what the transition and set QNH as soon as you are cleared to altitude regardless of what FL you are at. If ATC want a check of alt. or FL when you have the other set use the standby and in the unlikely event that you are asked to stop at a intermediate level then just change the setting and level off.

I would suggest that the original posters airline are out of step with majority of other operators in this respect and are asking for a level bust.