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RRUltrafan
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Barometer settings

Mon Mar 05, 2018 12:53 pm

In the flight sim I use, after I take off, the checklist tells me to set barometers to 'STD' as required. What does STD stand for? I can't seem to find any information on it by googling it. And why is the standard QNH setting 1013.25 hPa or 29.92 in Hg?
 
N757ST
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Re: Barometer settings

Mon Mar 05, 2018 1:19 pm

Standard atmosphere is 29.92 because if you were to measure the earths atmospheric pressure at sea level, pole to pole the average would be 29.92.

Different countries have different transition altitudes that you switch an altimeter from local to STD. In the United States any altitude at or above 18,000 an aircraft switches to 29.92.
 
T1a
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Re: Barometer settings

Mon Mar 05, 2018 2:03 pm

Yes, you are exactly right. In cruise flight airliners are assigned “Flight Levels“, which are essentually altitudes in relation to a 1013.25 hPa baro setting; minus the last two zeros. So FL350 is 35000ft on 1013.25.
Depending on A/C type the Instruments will display 1013 (29.92) or Std after setting the altimeter to standard, which is usually accomplished by pulling/pushing the baro knob.
Transition altitudes in Europe are between 3000ft and 10000ft depending on country.
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CFI4LIFE
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Re: Barometer settings

Mon Mar 05, 2018 2:53 pm

RRUltrafan wrote:
In the flight sim I use, after I take off, the checklist tells me to set barometers to 'STD' as required. What does STD stand for? I can't seem to find any information on it by googling it. And why is the standard QNH setting 1013.25 hPa or 29.92 in Hg?


Just set your altimeter to 29.92 when climbing through 18,000 and use the local altimeter setting when descending back through. When I played flight sims I always set the local altimeters, in the custom weather section, to 29.92 so I wouldn't have to bother with it in flight. :lol:
 
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Starlionblue
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Re: Barometer settings

Tue Mar 06, 2018 12:15 am

RRUltrafan wrote:
In the flight sim I use, after I take off, the checklist tells me to set barometers to 'STD' as required. What does STD stand for? I can't seem to find any information on it by googling it. And why is the standard QNH setting 1013.25 hPa or 29.92 in Hg?


Nitpick: While they are, in fact, adjustable barometers, they are referred to as "altimeters".
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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vhqpa
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Re: Barometer settings

Tue Mar 06, 2018 5:33 am

Transition altitudes in a couple of different countries:

Australia TA - 10,000' TL - FL110
New Zealand TA - 13,000' TL - FL150
United Kingdom TA - 6,000'
France TA - 5,000'
Germany TA - 5,000'
Netherlands TA - 3,000' (or is it 4,000'?)
Denmark TA - 5,000'
Sweden TA - 5,000'
Norway TA - 7,000'
USA TA - 18,000' TL - FL180
Canada TA - 18,000' (I pressume TL is FL180 like the US)

AFAIK Some countries have pre defined Transition Levels others are set by ATC depending on atmospheric conditions.
"There you go ladies and gentleman we're through Mach 1 the speed of sound no bumps no bangs... CONCORDE"
 
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TOGA10
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Re: Barometer settings

Tue Mar 06, 2018 10:15 am

vhqpa wrote:
Transition altitudes in a couple of different countries:
Netherlands TA - 3,000' (or is it 4,000'?)

Correct, it is 3,000' in the Netherlands.
I think part of the reason why it's different in some countries is (the lack of) high terrain. If there is high terrain, you want to switch to STD later/higher. That way your terrain clearance is guaranteed on that day with the current atmospheric conditions. With a very low pressure, and STD set, you are flying lower than you might think.
The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine. - Plato
 
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Starlionblue
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Re: Barometer settings

Tue Mar 06, 2018 10:29 am

QNH setting seems almost trivial sometimes but it is one of the more important things we do. Which is why it is cross-checked every time and included in checklists.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
CosmicCruiser
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Re: Barometer settings

Tue Mar 06, 2018 1:20 pm

I remember France giving it on the ATIS. In fact there were 2 times I had a little issue with the F/O being a little complacent. We were descending into CDG and were told to descend to 70 or 7,000, I missed it. I asked the F/O which was it and he replied "I think it was 7,000". I said to ask to be sure. It was fl70! Another time it was a perfect set up fo a mistake. Again going into CDG we were descending below the transition and our chk list called for "altimeters". Ironically the the QNH was 992mb so I had mine set and the F/O just replied "992". He was flying and hadn't made the change from QNE 9.92!(which means he hadn't made the change to 1013 at 30west) As we went thru 4,000' I caught it and brought the jet back up to 4,000. Thankfully CDG app. never said anything and all was well. I reminded the F/O when outside the US ALWAYS reply to altimeter settings in inches or MB. I also began the habit of checking the F/O's altimeter too.
UK was always very low too; like 3,000. We had a couple of guys bust altitudes when asked to level off just passed the transition in a very light wgt MD-11!
I was always told it's 18,000 in the US because that's the 500mb lvl.
 
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TOGA10
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Re: Barometer settings

Tue Mar 06, 2018 2:32 pm

CosmicCruiser wrote:
I remember France giving it on the ATIS. In fact there were 2 times I had a little issue with the F/O being a little complacent. We were descending into CDG and were told to descend to 70 or 7,000, I missed it. I asked the F/O which was it and he replied "I think it was 7,000". I said to ask to be sure. It was fl70! Another time it was a perfect set up fo a mistake. Again going into CDG we were descending below the transition and our chk list called for "altimeters". Ironically the the QNH was 992mb so I had mine set and the F/O just replied "992". He was flying and hadn't made the change from QNE 9.92!(which means he hadn't made the change to 1013 at 30west) As we went thru 4,000' I caught it and brought the jet back up to 4,000. Thankfully CDG app. never said anything and all was well. I reminded the F/O when outside the US ALWAYS reply to altimeter settings in inches or MB. I also began the habit of checking the F/O's altimeter too.
UK was always very low too; like 3,000. We had a couple of guys bust altitudes when asked to level off just passed the transition in a very light wgt MD-11!
I was always told it's 18,000 in the US because that's the 500mb lvl.

I think this is a perfect example of why stuff like this needs to be standardised! Thanks for your reply.
The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine. - Plato
 
DashTrash
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Re: Barometer settings

Tue Mar 06, 2018 11:58 pm

vhqpa wrote:
Transition altitudes in a couple of different countries:

Australia TA - 10,000' TL - FL110
New Zealand TA - 13,000' TL - FL150
United Kingdom TA - 6,000'
France TA - 5,000'
Germany TA - 5,000'
Netherlands TA - 3,000' (or is it 4,000'?)
Denmark TA - 5,000'
Sweden TA - 5,000'
Norway TA - 7,000'
USA TA - 18,000' TL - FL180
Canada TA - 18,000' (I pressume TL is FL180 like the US)

AFAIK Some countries have pre defined Transition Levels others are set by ATC depending on atmospheric conditions.

There is a difference between "transition level" and "transition altitude". In some countries you set standard in the climb at the transition altitude and on the way down you set it at the transition level. Australia and New Zealand are two examples on your list.
 
CosmicCruiser
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Re: Barometer settings

Wed Mar 07, 2018 2:00 pm

for a real thrill we used to fly into Almaty where, for a long time, they used QFE below the transition level so you would see the altimeter unwind to the tune of about 5,000' and if in the clouds knowing there's big mountains nearby it was exciting to say the least.
 
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Semaex
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Re: Barometer settings

Wed Mar 07, 2018 2:09 pm

RRUltrafan wrote:
In the flight sim I use, after I take off, the checklist tells me to set barometers to 'STD' as required. What does STD stand for? I can't seem to find any information on it by googling it. And why is the standard QNH setting 1013.25 hPa or 29.92 in Hg?


The standart setting (29.92 inHG in the US, 1013.25 hPA in most other countries) exists because it relates to the "standart atmosphere" determined by the international meteorological society.
This "standart atmosphere" is measured at sea level and has a certain pressure (as mentioned) and a certain temperature (15°C). These values were chosen because they are about an average of your typical atmosphere on a given day at about 40° latitude.



TOGA10 wrote:
CosmicCruiser wrote:
I remember France giving it on the ATIS. In fact there were 2 times I had a little issue with the F/O being a little complacent. We were descending into CDG and were told to descend to 70 or 7,000, I missed it. I asked the F/O which was it and he replied "I think it was 7,000". I said to ask to be sure. It was fl70! Another time it was a perfect set up fo a mistake. Again going into CDG we were descending below the transition and our chk list called for "altimeters". Ironically the the QNH was 992mb so I had mine set and the F/O just replied "992". He was flying and hadn't made the change from QNE 9.92!(which means he hadn't made the change to 1013 at 30west) As we went thru 4,000' I caught it and brought the jet back up to 4,000. Thankfully CDG app. never said anything and all was well. I reminded the F/O when outside the US ALWAYS reply to altimeter settings in inches or MB. I also began the habit of checking the F/O's altimeter too.
UK was always very low too; like 3,000. We had a couple of guys bust altitudes when asked to level off just passed the transition in a very light wgt MD-11!
I was always told it's 18,000 in the US because that's the 500mb lvl.

I think this is a perfect example of why stuff like this needs to be standardised! Thanks for your reply.


I'm all for standardisation! However, countries which are in general at higher altitudes will not exactly profit from a lower transition altitude.
Same as countries with lots of VFR traffic in the lower airspace (ie US -> TA 180)
And countries with a lot of IFR traffic in the lower airspace (anywhere in Europe) will also not be able to adhere to local altimeter settings every couple of minutes or when crossing a border.
// You know you're an aviation enthusiast if you look at your neighbour's cars and think about fleet commonality.
 
Redbellyguppy
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Re: Barometer settings

Wed Mar 07, 2018 3:01 pm

Depending on what plane you are simming, building a proper flight plan in the fmc should prompt your altimeter to blink or turn yellow at the appropriate transition altitude for your aircraft's geo location.
 
CosmicCruiser
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Re: Barometer settings

Wed Mar 07, 2018 3:46 pm

not true for every FMS. We didn't have it.
 
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TOGA10
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Re: Barometer settings

Thu Mar 08, 2018 8:42 am

Removed due to error in quoting previous post. Mods, feel free to delete!
Last edited by TOGA10 on Thu Mar 08, 2018 8:46 am, edited 3 times in total.
The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine. - Plato
 
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TOGA10
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Re: Barometer settings

Thu Mar 08, 2018 8:45 am

Semaex wrote:
RRUltrafan wrote:
In the flight sim I use, after I take off, the checklist tells me to set barometers to 'STD' as required. What does STD stand for? I can't seem to find any information on it by googling it. And why is the standard QNH setting 1013.25 hPa or 29.92 in Hg?


The standart setting (29.92 inHG in the US, 1013.25 hPA in most other countries) exists because it relates to the "standart atmosphere" determined by the international meteorological society.
This "standart atmosphere" is measured at sea level and has a certain pressure (as mentioned) and a certain temperature (15°C). These values were chosen because they are about an average of your typical atmosphere on a given day at about 40° latitude.



TOGA10 wrote:
CosmicCruiser wrote:
I remember France giving it on the ATIS. In fact there were 2 times I had a little issue with the F/O being a little complacent. We were descending into CDG and were told to descend to 70 or 7,000, I missed it. I asked the F/O which was it and he replied "I think it was 7,000". I said to ask to be sure. It was fl70! Another time it was a perfect set up fo a mistake. Again going into CDG we were descending below the transition and our chk list called for "altimeters". Ironically the the QNH was 992mb so I had mine set and the F/O just replied "992". He was flying and hadn't made the change from QNE 9.92!(which means he hadn't made the change to 1013 at 30west) As we went thru 4,000' I caught it and brought the jet back up to 4,000. Thankfully CDG app. never said anything and all was well. I reminded the F/O when outside the US ALWAYS reply to altimeter settings in inches or MB. I also began the habit of checking the F/O's altimeter too.
UK was always very low too; like 3,000. We had a couple of guys bust altitudes when asked to level off just passed the transition in a very light wgt MD-11!
I was always told it's 18,000 in the US because that's the 500mb lvl.

I think this is a perfect example of why stuff like this needs to be standardised! Thanks for your reply.


I'm all for standardisation! However, countries which are in general at higher altitudes will not exactly profit from a lower transition altitude.
Same as countries with lots of VFR traffic in the lower airspace (ie US -> TA 180)
And countries with a lot of IFR traffic in the lower airspace (anywhere in Europe) will also not be able to adhere to local altimeter settings every couple of minutes or when crossing a border.

No, I'm happy with a different TL/TA, this is depicted on charts anyway, but I meant, we should all adhere to either hecto pascal or inHg. Pretty much everything else is standard in the western world, why not this? Then again, weather report in the US are with VIS in SM as well, so maybe not as standard as one would hope.
The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine. - Plato
 
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Starlionblue
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Re: Barometer settings

Thu Mar 08, 2018 8:58 am

TOGA10 wrote:
Semaex wrote:
RRUltrafan wrote:
In the flight sim I use, after I take off, the checklist tells me to set barometers to 'STD' as required. What does STD stand for? I can't seem to find any information on it by googling it. And why is the standard QNH setting 1013.25 hPa or 29.92 in Hg?


The standart setting (29.92 inHG in the US, 1013.25 hPA in most other countries) exists because it relates to the "standart atmosphere" determined by the international meteorological society.
This "standart atmosphere" is measured at sea level and has a certain pressure (as mentioned) and a certain temperature (15°C). These values were chosen because they are about an average of your typical atmosphere on a given day at about 40° latitude.



TOGA10 wrote:
I think this is a perfect example of why stuff like this needs to be standardised! Thanks for your reply.


I'm all for standardisation! However, countries which are in general at higher altitudes will not exactly profit from a lower transition altitude.
Same as countries with lots of VFR traffic in the lower airspace (ie US -> TA 180)
And countries with a lot of IFR traffic in the lower airspace (anywhere in Europe) will also not be able to adhere to local altimeter settings every couple of minutes or when crossing a border.

No, I'm happy with a different TL/TA, this is depicted on charts anyway, but I meant, we should all adhere to either hecto pascal or inHg. Pretty much everything else is standard in the western world, why not this? Then again, weather report in the US are with VIS in SM as well, so maybe not as standard as one would hope.


Don't forget metric flight levels in China. ;)
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Semaex
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Re: Barometer settings

Thu Mar 08, 2018 10:56 am

Starlionblue wrote:
Don't forget metric flight levels in China. ;)


Please don't start! :D


TOGA10 wrote:
And countries with a lot of IFR traffic in the lower airspace (anywhere in Europe) will also not be able to adhere to local altimeter settings every couple of minutes or when crossing a border.

No, I'm happy with a different TL/TA, this is depicted on charts anyway, but I meant, we should all adhere to either hecto pascal or inHg. Pretty much everything else is standard in the western world, why not this? Then again, weather report in the US are with VIS in SM as well, so maybe not as standard as one would hope.[/quote]

Agreed!
Naturally, I'm pro metric system ;)
// You know you're an aviation enthusiast if you look at your neighbour's cars and think about fleet commonality.

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