When to change to 1013mb?
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When to change to 1013mb?
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
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
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HP, I realise you are asking for a reply from the ATC perspective but surely the UK AIP (ENR 1.7) is quite clear on this?
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
ENR 1.7 — ALTIMETER SETTING PROCEDURES
5 Detailed 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 Landing5.1.5 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.
5.3.1 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
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altimeter setting procedures
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
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
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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
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
Last edited by Jumbo Driver; 20th May 2008 at 10:36. Reason: Mode C reference
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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??
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??
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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.
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.
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ENR 1.7 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
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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.
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.
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Best wishes ...
JD
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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.
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.
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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).
Incidentally, Mode C is always referenced to 1013, irrespective of any altimeter setting.
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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
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
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As I said, Mode C in the aircraft never uses QNH.
JD
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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 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.
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.
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.
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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.
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.
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HP - glad we sorted that out!
Your 'colleague' is essentially correct
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.
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.
"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.