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What Does QNH Mean?  
User currently offlineDC-10 Levo From United Kingdom, joined Nov 2001, 3432 posts, RR: 3
Posted (11 years 3 months 2 weeks 1 day 1 hour ago) and read 14969 times:

 Smile Hi everyone!  Smile

Sometimes when I listen on my scanner I hear something like:

"East Midlands Approach, good morning Golf Charlie Uniform with you 3,000ft."

The controller will respond and then the pilot will say something like:

"QNH (some numbers) Sqwark 2846."

What does QNH mean?

Thanks for your replies.

DC-10

14 replies: All unread, jump to last
 
User currently offlineBen88 From United States of America, joined Dec 1999, 1093 posts, RR: 3
Reply 1, posted (11 years 3 months 2 weeks 1 day 1 hour ago) and read 14960 times:

Barometer

sdfsdfsdfsdfsdfsdfds


User currently offlineSabena 690 From , joined Dec 1969, posts, RR:
Reply 2, posted (11 years 3 months 2 weeks 1 day 1 hour ago) and read 14963 times:

Isn't that for the transponder code?

No idea otherwise...

EDIT: now I remember: hasn't this something to do with the barometer? Because they say a lot QNH 1013...

[Edited 2003-04-12 13:03:48]

User currently offlineLYNDON From United Kingdom, joined Aug 2001, 129 posts, RR: 0
Reply 3, posted (11 years 3 months 2 weeks 1 day 1 hour ago) and read 14957 times:

Think its something to do with the air pressure and it affects an aircrafts altimeter ?

User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 4, posted (11 years 3 months 2 weeks 1 day 1 hour ago) and read 14951 times:

Q-codes have been around for awhile, as you can see.

http://www.kloth.net/radio/qcodes#qaa

QNE and QNH are listed towards the end of the first section.

When ATC gives an aircraft its QNH (expressed in inches of mercury here in the US, or hectopascals elsewhere), the crew then sets their aircraft altimeters to that setting, so that their displayed altitude is with reference to that airport.


User currently offlineDC-10 Levo From United Kingdom, joined Nov 2001, 3432 posts, RR: 3
Reply 5, posted (11 years 3 months 2 weeks 1 day ago) and read 14918 times:

Oh, thanks for the help.

(I've even heard it whilst listening to police aswell, but I think thats just QNE.)

DC-10


User currently offlineSkymonster From , joined Dec 1969, posts, RR:
Reply 6, posted (11 years 3 months 2 weeks 1 day ago) and read 14912 times:

The value given after the QNH (e.g. East Midlands QNH one-zero-one-three) is the value that has to be set on the airplane's altimeter to make the altimeter display the aircraft's altitude above mean-sea-level. If the East Midlands QNH is one-zero-one-three, setting 1013 on the airplane's altimeter whilst the airplane is on the ground at East Midlands will result in the altimeter showing around 300 feet depending on exactly where the airplane is at EMA, as 300 feet is the approximate elevation of East Midlands Airport.

QNH has to be set on the altimeter because the air pressure at a specific location varies day by day, hour by hour, minute by minute, and this affects the altimeter's reading. To ensure that all airplanes are using the same setting and reference point, all airplanes operating in or near an airfield set the airfield's local QNH.

Setting QNH makes an altimeter show altitude above mean sea level, whereas setting QFE (which you will also have heard) makes an altimeter show height above the airfield elevation - in the UK, QFE is usually used for landings so that the altimeter reads zero on touchdown, QNH is used for flying around the general area as pressure can vary from area to area and this ensures that everyone is using the same value.

At East Midlands, the QNH will usually be around 10 higher than the QFE (e.g. QNH 1013, QFE 1003) as each hectopascal is the equivalent of approximately 30 feet - the total difference of 10 hectopascals represents 300 feet, which again is the approximate height of EMA above sea level.

Hope this helps,

Andy (private pilot flying from East Midlands from time to time!!!)


User currently offlineTsentsan From Singapore, joined Jan 2002, 2016 posts, RR: 15
Reply 7, posted (11 years 3 months 2 weeks 23 hours ago) and read 14904 times:

If you want to know what QNH stands for, it means... Question Nil Height. This goes back to older times where a/c wanted to know what was the pressure at 0 height which was the airport elevation.




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User currently offlineDC-10 Levo From United Kingdom, joined Nov 2001, 3432 posts, RR: 3
Reply 8, posted (11 years 3 months 2 weeks 23 hours ago) and read 14887 times:

Thanks guys!

DC-10


User currently offlineAvroArrow From Canada, joined Sep 2001, 1045 posts, RR: 0
Reply 9, posted (11 years 3 months 2 weeks 22 hours ago) and read 14855 times:

And to think, over here we just call it the altimeter setting when dealing with ATC and ATIS.  Smile/happy/getting dizzy


Give me a mile of road and I can take you a mile. Give me a mile of runway and I can show you the world.
User currently offlineTimz From United States of America, joined Sep 1999, 6778 posts, RR: 7
Reply 10, posted (11 years 3 months 2 weeks 14 hours ago) and read 14777 times:

I think Skymonster covered it; Tsentsan was the one that got careless.

User currently offlineSnoopy From Switzerland, joined Oct 2001, 370 posts, RR: 0
Reply 11, posted (11 years 3 months 2 weeks 14 hours ago) and read 14758 times:

"If you want to know what QNH stands for, it means... Question Nil Height. This goes back to older times where a/c wanted to know what was the pressure at 0 height which was the airport elevation."

Just to be picky  Smile

QNH actually gives the air pressure at sea-level. If you set this on your altimeter, your altimeter will show the airfield altitude when you are on the tarmac.

If you set QFE, which is the air pressure at airport altitude (Field Elevation), your altimeter will show "0" on the tarmac.


User currently offlineLamyl_hhlco From United States of America, joined Aug 2000, 621 posts, RR: 2
Reply 12, posted (11 years 3 months 2 weeks 7 hours ago) and read 14713 times:

it's simply the athmospheric pressure above sea level, equivalent as Altimeter pressure in US.

User currently offlineTsentsan From Singapore, joined Jan 2002, 2016 posts, RR: 15
Reply 13, posted (11 years 3 months 2 weeks 5 hours ago) and read 14696 times:

Apologies, muz have mixed them up somewhere  Sad But thanks good for learning Big grin


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User currently offlineMarkTpa From United States of America, joined Jun 2000, 97 posts, RR: 3
Reply 14, posted (11 years 3 months 1 week 6 days 18 hours ago) and read 14647 times:

I think the guys above covered it well. It is another way of stating the Altimeter setting. I hear it all the time when I fly into NAS or FPO.

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