Standby ALTIMETER SETTING CHANGE
Join Date: Feb 2001
Location: Hants, UK
Posts: 1,064
Likes: 0
Received 0 Likes
on
0 Posts
As a Pilot and an ATCO:
When departing and cleared to a flight level, I will set the main altimeter to 1013 when passing MSA and leave the standby on the aerodrome QNH.
I expect a similar approach from the traffic I control. If you are cleared to a flight level, it should be terrain safe and it is the FLIGHT LEVEL, not the ALTITUDE which is providing your separation against the traffic above which is, presumably, also operating on 1013. If cleared to a FL and not asked for intermediate altitude reports, set 1013 as soon as you are above MSA.
In times of low QNH, a delay in setting 1013 until TA can end in tears.
Consider this:
High performance biz jet departing on a QNH of 983mb. Initial SID level is 4000ft, and the aircraft is subsequently cleared to FL 80 against traffic at FL90. TA is 6000ft. The crew, with the a/c climbing at 3000fpm, delay resetting altimeters until passing 6000ft.
6000ft on a QNH of 983 mb is approx FL 69. By the time the crew have set the altimeter to 1013 passing 6000ft at 3000fpm, the aircraft will be passing FL75 or more, with 6 seconds or less for the autopilot to capture the new level and start the level off. Chances of a level bust or worse very high.
There have been more than a few Airproxes in just this scenario.
When departing and cleared to a flight level, I will set the main altimeter to 1013 when passing MSA and leave the standby on the aerodrome QNH.
I expect a similar approach from the traffic I control. If you are cleared to a flight level, it should be terrain safe and it is the FLIGHT LEVEL, not the ALTITUDE which is providing your separation against the traffic above which is, presumably, also operating on 1013. If cleared to a FL and not asked for intermediate altitude reports, set 1013 as soon as you are above MSA.
In times of low QNH, a delay in setting 1013 until TA can end in tears.
Consider this:
High performance biz jet departing on a QNH of 983mb. Initial SID level is 4000ft, and the aircraft is subsequently cleared to FL 80 against traffic at FL90. TA is 6000ft. The crew, with the a/c climbing at 3000fpm, delay resetting altimeters until passing 6000ft.
6000ft on a QNH of 983 mb is approx FL 69. By the time the crew have set the altimeter to 1013 passing 6000ft at 3000fpm, the aircraft will be passing FL75 or more, with 6 seconds or less for the autopilot to capture the new level and start the level off. Chances of a level bust or worse very high.
There have been more than a few Airproxes in just this scenario.
Join Date: Jan 2003
Location: The Heart
Posts: 811
Likes: 0
Received 0 Likes
on
0 Posts
Fireflybob.
The climb instruction is "climb with min gradient 6.6% to FL70". The TA is 5000'.
Having the QNH in the standby alt isn't going to get the autopilot to level off at an altitude.
Now, with the input of some ATC types, we can see a pattern emerging. If you have the QNH set up to TA then you can stop the climb and report alt passing. Then at TA set 1013 and do the after take-off checklist.
Everything gets done at an appropriate time, nothing gets left out and you can comply with any request or necessity at any time.
I don't have plates handy for anywhere with a 9000' MSA, but I can't find any TA lower than MSA.
The climb instruction is "climb with min gradient 6.6% to FL70". The TA is 5000'.
Having the QNH in the standby alt isn't going to get the autopilot to level off at an altitude.
Now, with the input of some ATC types, we can see a pattern emerging. If you have the QNH set up to TA then you can stop the climb and report alt passing. Then at TA set 1013 and do the after take-off checklist.
Everything gets done at an appropriate time, nothing gets left out and you can comply with any request or necessity at any time.
I don't have plates handy for anywhere with a 9000' MSA, but I can't find any TA lower than MSA.
Well in the US with its altimetry, the controller has QNHs for the airports in the area and it is transmitted upon initial contact, if operating below FL180. The QNH is given with the descent clearance below TA/TL for the area. Yes, controllers forget and pilots ask, so its not perfect, but FL180 gives everyone time to straighten it out. VFR pilots are responsible to periodically get a QNH, how well that works I'm not prepared to say.
Usually on the hand-off to arrival control, you'll get a QNH for that airport. For the crew, it works because you can do the approach/in-range check early enough for the altimeters to be set prior to getting vectors or prior to the IAF.
I was an Eastern Airlines (dearly missed) and we used QFE almost to the end and had all sorts of peculiar altimetry procedures using QFE on the main altimeters and QNH on third altimeter. We both had to refer to the third when being vectored and change over to the mains for the actual approach.
There is nothing sacred about FL180, but, as a pilot, I like the idea of being on QNH once I've descended below the highest terrain.
Usually on the hand-off to arrival control, you'll get a QNH for that airport. For the crew, it works because you can do the approach/in-range check early enough for the altimeters to be set prior to getting vectors or prior to the IAF.
I was an Eastern Airlines (dearly missed) and we used QFE almost to the end and had all sorts of peculiar altimetry procedures using QFE on the main altimeters and QNH on third altimeter. We both had to refer to the third when being vectored and change over to the mains for the actual approach.
There is nothing sacred about FL180, but, as a pilot, I like the idea of being on QNH once I've descended below the highest terrain.
Join Date: Mar 2002
Location: Euroland
Posts: 2,814
Likes: 0
Received 0 Likes
on
0 Posts
MIserlou,
Check out Scotland north of Glasgow.
Highest obstacle is Ben Nevis (over 4000ft) and the transition altitude away from the main airports is 3000ft.
One thing that I have noticed in the UK is that the transition level is calculated as the flight level closest to and above the transition altitude. Thus there is no vertical separation between the transition altitude and the transition level.
When flying in Ireland, the transition level is quoted on the ATIS and is always separated from the transition altitude.
Perhaps people from other countries could state if their "transition level" is separated from the transition altitude or not.
Why with the same (ICAO) definition of transition level do two adjacent FIRs use totally different methods for it's calculation?
I must admit that I am in favour of having the transition level separated from the transition altitude for obvious reasons. I am also in favour of having the TL on the ATIS so that we can get a mental picture of how deep the transition layer is...............if TA is 5000ft and the TL is FL75..........we can instantly see that having changed to 1013 after being cleared to a FL, we are at the MSA of 3500ft after passing FL50. easy.
Regards,
DFC
Check out Scotland north of Glasgow.
Highest obstacle is Ben Nevis (over 4000ft) and the transition altitude away from the main airports is 3000ft.
One thing that I have noticed in the UK is that the transition level is calculated as the flight level closest to and above the transition altitude. Thus there is no vertical separation between the transition altitude and the transition level.
When flying in Ireland, the transition level is quoted on the ATIS and is always separated from the transition altitude.
Perhaps people from other countries could state if their "transition level" is separated from the transition altitude or not.
Why with the same (ICAO) definition of transition level do two adjacent FIRs use totally different methods for it's calculation?
I must admit that I am in favour of having the transition level separated from the transition altitude for obvious reasons. I am also in favour of having the TL on the ATIS so that we can get a mental picture of how deep the transition layer is...............if TA is 5000ft and the TL is FL75..........we can instantly see that having changed to 1013 after being cleared to a FL, we are at the MSA of 3500ft after passing FL50. easy.
Regards,
DFC
TA in Scotland is A060, not A030 like England (except under London CTA where it's A060, apart from alternate Thursdays in months ending in '...er' unless you have 7 altimeters & specific JAR-OPs/CAA approved dispensation to operate.... ) 
Oz TA is A100, TL is F110. This gives 1000' buffer. As QNH reduces below 1013 the minimum available FL for use increases to maintain at least 1000' separation between the two systems eg min allowable FL could be F115, or F120 etc.
Very like the US system. A100 works well. The highest mountain is less than 8000' & A100 is a nice, easy to remember number.
Oz TA is A100, TL is F110. This gives 1000' buffer. As QNH reduces below 1013 the minimum available FL for use increases to maintain at least 1000' separation between the two systems eg min allowable FL could be F115, or F120 etc.
Very like the US system. A100 works well. The highest mountain is less than 8000' & A100 is a nice, easy to remember number.
Join Date: Mar 2002
Location: Euroland
Posts: 2,814
Likes: 0
Received 0 Likes
on
0 Posts
Inverness, Scotland.....TA 3000ft unless the Jepp is wrong. (Hope not!! ) 
As far as I am aware, in the UK the transition altitude is 3000ft except where in the vicinity of an airport a higher altitude is notified.
So the Australian system also ensures that the TA and TL are verticaly separated.
I can't figure out why the UK does not ensure that an aircraft at the transition level is vertically separated from an aircraft at the transition altitude.
IMHO, this could have safety implications where outbound aircraft climb on a SID to the TA.......if an inbound descends to the transition level in the UK, it will get very close to the outbound.
Perhaps, getting the calculation of transition level standardised would be a good first step. After all, not much point having a common TA if every FIR calculates the TL differently.
Regards,
DFC
As far as I am aware, in the UK the transition altitude is 3000ft except where in the vicinity of an airport a higher altitude is notified.
So the Australian system also ensures that the TA and TL are verticaly separated.
I can't figure out why the UK does not ensure that an aircraft at the transition level is vertically separated from an aircraft at the transition altitude.
IMHO, this could have safety implications where outbound aircraft climb on a SID to the TA.......if an inbound descends to the transition level in the UK, it will get very close to the outbound.
Perhaps, getting the calculation of transition level standardised would be a good first step. After all, not much point having a common TA if every FIR calculates the TL differently.
Regards,
DFC
Join Date: Apr 2003
Location: HotnDusty
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
Spitoon
"As a controller, I would expect the pilot of any high-performance aircraft to be able to follow my instructions/requests. If the cleared level is an altitude, I would expect level reports etc to be QNH-based, if it's a FL, I would expect level to be referenced to 1013."
Spitoon, how would you manage a (fairly common) scenario where one aircraft is cleared to an altitude and the next one to a FL by approach control. Isn't the idea of the first reporting altitudes and the next FL's liable to lead to confusion regarding their actual separation?
"As a controller, I would expect the pilot of any high-performance aircraft to be able to follow my instructions/requests. If the cleared level is an altitude, I would expect level reports etc to be QNH-based, if it's a FL, I would expect level to be referenced to 1013."
Spitoon, how would you manage a (fairly common) scenario where one aircraft is cleared to an altitude and the next one to a FL by approach control. Isn't the idea of the first reporting altitudes and the next FL's liable to lead to confusion regarding their actual separation?
Join Date: Feb 2001
Location: Hants, UK
Posts: 1,064
Likes: 0
Received 0 Likes
on
0 Posts
arrow1
In the UK at least, we usually calculate the flight level which will give at least 1000ft above the highest altitude.
In the London TMA, where the maximum SID altitude is 6000ft, the lowest FL will be that which equates to an altitude of 7000ft or more. So in times of low pressure, the lowest FL might be FL80. Conversely, in times of very high pressure we never use less than FL70. So it can take a long time to get from 6000ft altitude to FL70 or above, and this can prove embarrassing if you're not ready for it.
(For example: QNH 1040. 6000ft Altitude is approx FL 52. To climb and get separation of 1000ft above traffic at FL 70 you need to climb 2800ft instead of 2000ft. It can cause some tightening of the sphincter if you're trying to jump the stack!! )
So to answer your question more succinctly, the controller should know which flight levels are separated from altitudes and which are not.
In the UK at least, we usually calculate the flight level which will give at least 1000ft above the highest altitude.
In the London TMA, where the maximum SID altitude is 6000ft, the lowest FL will be that which equates to an altitude of 7000ft or more. So in times of low pressure, the lowest FL might be FL80. Conversely, in times of very high pressure we never use less than FL70. So it can take a long time to get from 6000ft altitude to FL70 or above, and this can prove embarrassing if you're not ready for it.
(For example: QNH 1040. 6000ft Altitude is approx FL 52. To climb and get separation of 1000ft above traffic at FL 70 you need to climb 2800ft instead of 2000ft. It can cause some tightening of the sphincter if you're trying to jump the stack!!
)So to answer your question more succinctly, the controller should know which flight levels are separated from altitudes and which are not.
Join Date: Jun 2001
Location: the Tearooms of Mars
Posts: 206
Likes: 0
Received 0 Likes
on
0 Posts
This is one of these things that there really shouldn’t be an SOP on. The setting should be up to the Captain for his own requirements. For many ‘standby’ quality altimeters, setting 1013.2 won’t give you the same indication as the main altimeters because it’s not derived from a digital air data computer, and CERTAINLY won’t be accurate enough for RVSM compliance.
If you feel that standard is a good setting then fine, over the Pond there might not be anything better to set, but don’t read into it more than is there. Personally I prefer to have the lowest QNH over the route I’m flying, and Zurich, Salzburg, Barcelona QNH respectively in those areas where terrain is a factor.
A good dose of Commanders discretion required.
If you feel that standard is a good setting then fine, over the Pond there might not be anything better to set, but don’t read into it more than is there. Personally I prefer to have the lowest QNH over the route I’m flying, and Zurich, Salzburg, Barcelona QNH respectively in those areas where terrain is a factor.
A good dose of Commanders discretion required.
Join Date: Apr 2003
Location: HotnDusty
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
eyeinthe sky
Thanks for the input. We have a similar system, while having QNH below the TA and 1013 above the TL and altitdues/FLs are reported accordingly. This means that the situation covered by "spitoon" wherein two aircraft on the same side of the the TL are reporting altitudes/FLs depending on what they are cleared to does not arise.
Thanks for the input. We have a similar system, while having QNH below the TA and 1013 above the TL and altitdues/FLs are reported accordingly. This means that the situation covered by "spitoon" wherein two aircraft on the same side of the the TL are reporting altitudes/FLs depending on what they are cleared to does not arise.
