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Altimeter 30.55

Wed Oct 10, 2001 10:37 am

...and that's what this post is about. I was listening to my scanner on LGA approach yesterday and today and I heard the planes getting the altimeter for the approach. The altimeter setting was at hightest 30.55". Isn't that high? I've never even heard it past about 30.25 or so, and I thought for a minute that it was a squawk or something when the pilots were saying "three zero five five, roger".
Does anyone here know the extremes for the barometer that have been documented?

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RE: Altimeter 30.55

Wed Oct 10, 2001 11:53 am

Didn't it creep above 31 in Alaska a few winters back? Did that cause some? many? most? aircraft to be grounded until it dropped?
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RE: Altimeter 30.55

Wed Oct 10, 2001 12:31 pm

A NOTAM will be issued if it drops below 28.00 and 32.00.. im quite sure those are the limits.
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RE: Altimeter 30.55

Wed Oct 10, 2001 4:40 pm

That isn't an uncommon reading in the middle of winter. Especially if it is really really really cold out. Say when it is -30 or -40 out.
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RE: Altimeter 30.55

Thu Oct 11, 2001 5:44 am

Does anyone know what that is in european measurements?

I know that 29.92 is 1013...

That is a very high pressure reading. Is that the QNH?

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RE: Altimeter 30.55

Thu Oct 11, 2001 1:11 pm

30.55 is 1034mb
It was a strange setting for this time of year in the US northeast, especially when it was around 29.88 (1012mb) 2 days prior.

No, QNH is 18,000 msl in the US. (Mt. McKinley in Alaska I believe).


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RE: Altimeter 30.55

Thu Oct 11, 2001 7:16 pm

No wonder that we have FL035 and such stuff in Europe  Smile .. plus 'backtrack'!

I seriously think I just creamed my pants without any influence from any outside variables.
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RE: Altimeter 30.55

Fri Oct 12, 2001 2:30 am

What does QNH stand for?

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RE: Altimeter 30.55

Sun Oct 14, 2001 5:08 am

Mount McKinley (Denali) is 20,320 feet high, not 18,000...you may have been thinking of Mount St. Elias, which is 18,008 feet high, in Alaska...

What is QNH????

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RE: Altimeter 30.55

Sun Oct 14, 2001 5:49 am

QNH is notation describing the altitude above sea level as opposed to QFE which is the altitude above the ground at the reporting station.

It has nothing to do with Mountains. 18,000 ASL is the transition altitude to standard altimeter setting in North America. Aircraft set the altimeter to 29.92 above this altitude. The transition altitude is different in other parts of the world.

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RE: Altimeter 30.55

Sun Oct 14, 2001 5:59 am


QFE=Question Field Elevation
QNH=Question Nill Height
QNE=Question Nill Elevation

QNE represents the transition altitude

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RE: Altimeter 30.55

Mon Oct 22, 2001 8:06 pm

QNH 1013 is a part of the ISA standard atmosphere.
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RE: Altimeter 30.55

Wed Oct 24, 2001 9:15 pm


Notice that the highest QNH was registered in the
North Pole...it was 1080mbs...unbelievable,but true!!!

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