18000' and FL180
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Here's my two cents worth:
In Ireland 5,000ft is the Trans Alt.
The Lowest Useable FL is the Trans level and that is between 1,000ft and 1,499ft above the TA (depending on QNH) .
In my experience, traffic climbing changes to 1013 passing through 5,000ft and reverts to QNH as he descends through whatever the Trans Level is at that time.
If the pilot changes is altimeter settings early it won't provide a false altitude indication as the Mode-C transmissions are all based on standard pressure. The radar software will convert the recieved Mode-C info and display it already adjusted to QNH if the aircraft is below the Trans Level. The only way a loss of separation should occur as a result of this is if the controller (having already cleared descent to Altitude) decides to stop descent at a FL, the pilot does not re-adjust his altimiter, and he levels off at an Altitude at or above the Trans level causing conflictions with other traffic operating on FL.
As for overlapping sectors with different TAs, there should be co-ord channels available between the controllers responsibile and the aircraft should change altimeter settings a specified time/distance before the boundary. The details should be in the LOA between the two sectors.
In Ireland 5,000ft is the Trans Alt.
The Lowest Useable FL is the Trans level and that is between 1,000ft and 1,499ft above the TA (depending on QNH) .
In my experience, traffic climbing changes to 1013 passing through 5,000ft and reverts to QNH as he descends through whatever the Trans Level is at that time.
If the pilot changes is altimeter settings early it won't provide a false altitude indication as the Mode-C transmissions are all based on standard pressure. The radar software will convert the recieved Mode-C info and display it already adjusted to QNH if the aircraft is below the Trans Level. The only way a loss of separation should occur as a result of this is if the controller (having already cleared descent to Altitude) decides to stop descent at a FL, the pilot does not re-adjust his altimiter, and he levels off at an Altitude at or above the Trans level causing conflictions with other traffic operating on FL.
As for overlapping sectors with different TAs, there should be co-ord channels available between the controllers responsibile and the aircraft should change altimeter settings a specified time/distance before the boundary. The details should be in the LOA between the two sectors.
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Nibog, the area being referred to where there is a problem with differing TA's between FIR's, involves mostly ex russian republic aircraft (TU-134's, YAKs etc), and so even if you get an agreement with Iran as to when they will switch aircraft etc (no mean feat), getting the aircraft to do the right thing is near impossible. That is why to be able to follow the KISS principle in this area would be ideal.
Radar Pete, seems strange that as you say the TA changes throughout Iran but the area I am referring to is the mountaneous area of the country with mountain peaks in the 14,000ft region, yet their TA is like 4,000ft below that. Confuses me, but then again thats not hard!
Radar Pete, seems strange that as you say the TA changes throughout Iran but the area I am referring to is the mountaneous area of the country with mountain peaks in the 14,000ft region, yet their TA is like 4,000ft below that. Confuses me, but then again thats not hard!
aceatco, retired
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Radar Pete, bookworm . . .
Think you may mean Doc 9426 ATS Planning Manual, Part II Sec 5 Ch 1 Altitmeter Setting Procedures although I don't see anything there which states the transition layer should be 1000ft. However the version I have access to is dated 1984 . . . .
It also refers to Doc 8168 vol 1
VA
Think you may mean Doc 9426 ATS Planning Manual, Part II Sec 5 Ch 1 Altitmeter Setting Procedures although I don't see anything there which states the transition layer should be 1000ft. However the version I have access to is dated 1984 . . . .
It also refers to Doc 8168 vol 1
VA
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Bookworm & Vintage ATCO
Hi guys. The manual has been updated a tad since 1984, I breezed through it the other day and it is now called the ATM Planning & Procedures Doc. This doc also replaces another (sorry forgotten the number) which is now obsolete.
Anyone have a good contact at ICAO???
ANSA
No comment on confusing you mate!!!! The TA changes in Iran and would be published. Those bits adjoining our FIR are essentially at MSL and thus have low TA's. The TA's in the mountaneous area would be higher and if not published would be based on the highest point within a certain radius + 1500', or something there abouts.
Hi guys. The manual has been updated a tad since 1984, I breezed through it the other day and it is now called the ATM Planning & Procedures Doc. This doc also replaces another (sorry forgotten the number) which is now obsolete.
Anyone have a good contact at ICAO???
ANSA
No comment on confusing you mate!!!! The TA changes in Iran and would be published. Those bits adjoining our FIR are essentially at MSL and thus have low TA's. The TA's in the mountaneous area would be higher and if not published would be based on the highest point within a certain radius + 1500', or something there abouts.
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Transition level
Surprised that nobody has yet mentioned the reasons for sometimes using altitude (terrain separation) and sometimes flight levels (worldwide standard pressure setting 1013.2 = 29.92 in Hg = 760 mm Hg).
Hence most states have set their tranisiton altitude to be slightly above the highest terrain in that FIR (Flight Information Region), in the case of Australia the highest LSALT is 8400' so TA at 10,000' allows at least one IFR and one VFR altitude in each direction over all of the country. Similarly in UK most of country is on TA of 3000' (though Snowdon 3560' amsl is also in this area) but Scottish FIR has TA 4000' (Ben Nevis 4406' also above it - but gives about 500' clearance between the FL that is 1000' above TA and the ground if the pressure is at or above 1013.
International convention gives us that the lowest usable IFR level must be at least minimum IFR separation (nominally 1000') above the transition altitude. Transition level is usually the nominal 1000' level above TA, but may not be usable if the QNH is below 1013 .
The USA is different because they have chosen to use altitude up to a level of FL 180, where they change airspace classification to Cleaa A (IFR only allowed to cruise there) - so the logic is different. Some pacific island states use 9500' as the TA because they have inherited that as the highest level that unpressurised VFRs can use, so everything pressurised will use FLs.
One of the responsibiliites of ATC when they have traffic approaching a boundary is to co-ordinate with the neighbouring sector to ensure vertical separation - just as important for any sector change, but more complex when there is a change in TA/TL or when (e.g. Russia and China) one sector uses 500 metre separation and metric altimetry, whilst the other side uses good old feet and flight levels.
Got it? Pity poor old Tibet, where FL 290 is LSALT on some routes across the Himalayas and the 747s from SIN and BKK to FRA and LHR don't have a big choice of levels due to traffic density on the route.
But it all beats the noise of aeroplanes bumping into each other!
Wombat too
Hence most states have set their tranisiton altitude to be slightly above the highest terrain in that FIR (Flight Information Region), in the case of Australia the highest LSALT is 8400' so TA at 10,000' allows at least one IFR and one VFR altitude in each direction over all of the country. Similarly in UK most of country is on TA of 3000' (though Snowdon 3560' amsl is also in this area) but Scottish FIR has TA 4000' (Ben Nevis 4406' also above it - but gives about 500' clearance between the FL that is 1000' above TA and the ground if the pressure is at or above 1013.
International convention gives us that the lowest usable IFR level must be at least minimum IFR separation (nominally 1000') above the transition altitude. Transition level is usually the nominal 1000' level above TA, but may not be usable if the QNH is below 1013 .
The USA is different because they have chosen to use altitude up to a level of FL 180, where they change airspace classification to Cleaa A (IFR only allowed to cruise there) - so the logic is different. Some pacific island states use 9500' as the TA because they have inherited that as the highest level that unpressurised VFRs can use, so everything pressurised will use FLs.
One of the responsibiliites of ATC when they have traffic approaching a boundary is to co-ordinate with the neighbouring sector to ensure vertical separation - just as important for any sector change, but more complex when there is a change in TA/TL or when (e.g. Russia and China) one sector uses 500 metre separation and metric altimetry, whilst the other side uses good old feet and flight levels.
Got it? Pity poor old Tibet, where FL 290 is LSALT on some routes across the Himalayas and the 747s from SIN and BKK to FRA and LHR don't have a big choice of levels due to traffic density on the route.
But it all beats the noise of aeroplanes bumping into each other!
Wombat too
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Similarly in UK most of country is on TA of 3000' (though Snowdon 3560' amsl is also in this area) but Scottish FIR has TA 4000' (Ben Nevis 4406' also above it - but gives about 500' clearance between the FL that is 1000' above TA and the ground if the pressure is at or above 1013.
UK AIP Altimeter Setting Procedures
(Note: you need to be registered with the NATS AIS site to access the document).
The UK doesn't publish Transition Levels as such, instead, they give a table from which you can find out the minimum Flight Level to cruise at based on the minimum altitude you want to fly at and the actual QNH. This table is found in the link above.
Alternatively, you can ask an ATS unit for the lowest Flight Level available. This may or may not be the Transition Level. For those in Controlled Airspace, this level will provide a minimum of 1000' vertical separation above the Transition Altitude.
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A fascinating discussion.
Eurocontrol has been studying this subject (common transition altitude) for over three years as far as I'm aware, and failed miserably to come up with a solution. Best they (41 member ECAC States) could agree on was a "regional CTA" but still that has not seen the light of day. So much for consensus.
But if you wish to get a better understanding of the issues and problems, then consider that some aerodromes (e.g. Lugarno) have 2 T/A's - one for each runway end, whilst some/most Eastern European States apply a different T/A for each runway direction - I.e 3 runways = 6 T/A. Now to spice it up a bit more, try Bulgaria where they specify "Transition Height"- I.e based on QFE.
Need more!!
Eurocontrol has been studying this subject (common transition altitude) for over three years as far as I'm aware, and failed miserably to come up with a solution. Best they (41 member ECAC States) could agree on was a "regional CTA" but still that has not seen the light of day. So much for consensus.
But if you wish to get a better understanding of the issues and problems, then consider that some aerodromes (e.g. Lugarno) have 2 T/A's - one for each runway end, whilst some/most Eastern European States apply a different T/A for each runway direction - I.e 3 runways = 6 T/A. Now to spice it up a bit more, try Bulgaria where they specify "Transition Height"- I.e based on QFE.
Need more!!
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Common Transition Altitude
Whilst the wheels of beaurocracy turn slowly, they at least seem to be turning, and a recent report from ACUSNA demonstrates that some people do understand the issues, and how best to resolve them.
ACNUSA = Authority for the control of noise disturbances at airports. It’s a French semi-governmental agency (directors appointed by the minister of transport) with considerable “clout”.
Translating from the French. Their glossy reads in summary:
• ACNUSA requests studies to raise the TA to above 10,000 ft for reasons of flight safety and better noise profiles near ILS intercept,
• From July to November 2003 studies (inter-alia; Paris ACC, Paris Approach Control, etc.) were undertaken and considered 6,000': 10,000': and 18,000'.
• Results were presented to ACNUSA 22-06-04,
• 10,000 ft is worse choice due to the Paris TMA airspace issues,
• 6,000 ft is an acceptable alternative which will improve upon the existing situation and which is relatively easy to implement,
• 18,000 ft is the best choice. However it clearly links 18,000 ft with the need to do this on a European-wide level given the interface problems.
As an outcome of the study the ACNUSA recommends to the French DGCA to undertake as a matter of urgency the necessary actions to address the French “European Neighbours”.
Report can be found at: [URL=http://www.acnusa.fr/rapports/pdf_2004/miseenoeuvrerecommandations2004.pdf[/URL]
On another front, the SE European region seem to be mustering their effort, and about to start consultations on how best they can address the Common TA issues. This is also a good sign that the old guard may be losing its grip on influence, and safety and sanity issues will, at last, prevail.
ACNUSA = Authority for the control of noise disturbances at airports. It’s a French semi-governmental agency (directors appointed by the minister of transport) with considerable “clout”.
Translating from the French. Their glossy reads in summary:
• ACNUSA requests studies to raise the TA to above 10,000 ft for reasons of flight safety and better noise profiles near ILS intercept,
• From July to November 2003 studies (inter-alia; Paris ACC, Paris Approach Control, etc.) were undertaken and considered 6,000': 10,000': and 18,000'.
• Results were presented to ACNUSA 22-06-04,
• 10,000 ft is worse choice due to the Paris TMA airspace issues,
• 6,000 ft is an acceptable alternative which will improve upon the existing situation and which is relatively easy to implement,
• 18,000 ft is the best choice. However it clearly links 18,000 ft with the need to do this on a European-wide level given the interface problems.
As an outcome of the study the ACNUSA recommends to the French DGCA to undertake as a matter of urgency the necessary actions to address the French “European Neighbours”.
Report can be found at: [URL=http://www.acnusa.fr/rapports/pdf_2004/miseenoeuvrerecommandations2004.pdf[/URL]
On another front, the SE European region seem to be mustering their effort, and about to start consultations on how best they can address the Common TA issues. This is also a good sign that the old guard may be losing its grip on influence, and safety and sanity issues will, at last, prevail.
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Of course there is potential for further confusion when one considers that mil ac undertaking certain activities, or in height blocks encompassing the TA, operate the Regional QNH (RPS) well above the transition altitude, and are only required to set the SAS at and above FL245.
This must seem odd to some of our civilian colleagues when a controller asks to coordinate not above, say, 22,500ft on an RPS of 1038 against traffic at FL 230.
BA
This must seem odd to some of our civilian colleagues when a controller asks to coordinate not above, say, 22,500ft on an RPS of 1038 against traffic at FL 230.
BA
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Military flights in civil airspace should follow civil airspace rules wrt altimetry.
Other than in segregated airspace (where there should be no requirement to coordinate against traffic under civil control), I cannot find any references to instances where military aircraft fly above the TA on RPS. Such flights will only be with SAS set. As far as I have been able to determine, this therefore covers the military in Bulgaria, Croatia, Germany, Norway, Portugal, Spain and UK, which seems a fairly representative cross-section of ECAC nations.
Can you provide detail as to where/when and how the procedures you describe occur?
Other than in segregated airspace (where there should be no requirement to coordinate against traffic under civil control), I cannot find any references to instances where military aircraft fly above the TA on RPS. Such flights will only be with SAS set. As far as I have been able to determine, this therefore covers the military in Bulgaria, Croatia, Germany, Norway, Portugal, Spain and UK, which seems a fairly representative cross-section of ECAC nations.
Can you provide detail as to where/when and how the procedures you describe occur?
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Military flights in civil airspace should follow civil airspace rules wrt altimetry.
Anyway, aircraft flying in class G in UK (civil or mil) may fly on any pressure they please, as long as they remain clear of controlled airspace, etc...
The example given is a situation that occurs very often in the UK. A military aircraft may be flying on RPS well above the TA and need to be co-ordinated against another aircraft (receiving a RAS) flying SAS. Some pressure based arithmetic needs to be done to ensure standard separation is maintained.
The reason a (typically military) aircraft might be flying on RPS is that it may be operating in a large altitude block, but requires to be accurately aware of it's base altitude to guarantee the flight isn't conducted dangerously low. This may even be against a Minimum Sector Safety Altitude which is greater than the Transition Altitude.
A considerate controller working such an aircraft should be aware of the equivalent airspace block being used in terms of Flight Levels and so a request to some of our civilian colleagues to coordinate not above, say, 22,500ft on an RPS of 1038 against traffic at FL 230 should not be necessary. The controller will know that 22,500ft on an RPS of 1038 equates to 21,750ft on SAS and ought to therefore offer co-ordination 'not above FL220'.
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What is 'civil airspace'? I'm not familiar with the term in the UK.
Anyway, aircraft flying in class G in UK (civil or mil) may fly on any pressure they please, as long as they remain clear of controlled airspace, etc...
The example given is a situation that occurs very often in the UK. A military aircraft may be flying on RPS well above the TA and need to be co-ordinated against another aircraft (receiving a RAS) flying SAS. Some pressure based arithmetic needs to be done to ensure standard separation is maintained.
The reason a (typically military) aircraft might be flying on RPS is that it may be operating in a large altitude block, but requires to be accurately aware of it's base altitude to guarantee the flight isn't conducted dangerously low. This may even be against a Minimum Sector Safety Altitude which is greater than the Transition Altitude.
A considerate controller working such an aircraft should be aware of the equivalent airspace block being used in terms of Flight Levels and so a request to some of our civilian colleagues to coordinate not above, say, 22,500ft on an RPS of 1038 against traffic at FL 230 should not be necessary. The controller will know that 22,500ft on an RPS of 1038 equates to 21,750ft on SAS and ought to therefore offer co-ordination 'not above FL220'.
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My instructor always told me to cruise between the TA and TL as it would be for safer as other pilots never cruise at that height/altitude/FL. The wouldn't know what to set on the altimerter pressure setting.
