Altimeter Question

WingFlaps schrieb:

QNH means query Newquay Harbour which was the British reference for
sea level.
It should give the atmospheric pressure at that dtaum -but I doubt

You certainly can cite a source for this urban legend?

terry wrote in news:234756e2-a583-4cbc-8f42-
:

I am confused by this practice commercial nav question. ( at least I
am confused by the answer in the book which was b. but I think both a
and c are correct), but I appreciate some other opinions.

Day 1 Altimeter reads elevation of 1390 feet with 1013 HPa set on
subscale
( thats equivalent to 29.92 inches of Hg for the US folks)
Day 2 Altimeter reads elevation of 1000 feet
Assuming the altimeter subscale was not changed between day 1 and day
2 it could be said that

a. The QNH is higher on day 2
b. The QNH is lower on day 2
c. The pressure altitude at the airport is lower on day 2
d. The atmospheric pressure at the aerodrome has not changed.

It's A. It could also be C if the airfield has a serious subsidance
problem.


Bertie

On Apr 18, 12:07*am, Bertie the Bunyip wrote:
terry wrote in news:234756e2-a583-4cbc-8f42-
:

I am confused by this practice commercial nav question. ( at least I
am confused by the answer in the book which was b. but I think both a
and c are correct), but I appreciate some other opinions.

Day 1 Altimeter reads elevation of 1390 feet with 1013 HPa set on
subscale
* * * * *( thats equivalent to 29.92 inches of Hg for the US folks)
Day 2 Altimeter reads elevation of 1000 feet
Assuming the altimeter subscale was not changed between day 1 and day
2 it could be said that

a. The QNH is higher on day 2
b. The QNH is lower on day 2
c. The pressure altitude at the airport is lower on day 2
d. *The atmospheric pressure at the aerodrome has not changed.

It's A. It could also be C if the airfield has a serious subsidance
problem.

you are really confusing me now Bertie, I got learned that the
pressure ht was wot your altimeter reads when you have 1013.2 in the
window ( or 29.92 for you ...or maybe not cos everyone knows bunyips
are aussies ) 1000 is lower than 1390 therefore pressure altitude is
lower on day 2.. surely!.

On Apr 17, 11:29*pm, Stefan wrote:
Larry Dighera schrieb:

*http://en.wikipedia.org/wiki/Mbar

Mbar would be a tad much. You certainly meant mbar.

* What does QNH stand for?
* Atmospheric Pressure (Q) at Nautical Height (aviation)

Bull****. QNH is *not* an acronym. It's one of over hundred Q-Codes
which were defined in the stone age of radio telephony. The letters were
randomly chosen, think of it as a numeration. Most of those Q-Codes are
forgotten today, but a few still live. In aviation, I mean in aviation
in all coutries except the USA, QNH, QFE and QNH are used to define
different altitude settings (roughly spoken).

QNH stands for the pressure you must tune in the kollmans window to have
the altimeter display the airport elevation when the airplane sits on
the ground. (As opposed to QFE, which ist the pressure to set for the
alitmeter to display zero on the ground and QNE, which is the altitude
which the alitmeter shows on the ground when it is set to standard
atmosphere.)

For those who believe in Wikipedia:http://en.wikipedia.org/wiki/Q-code

I wasnt aware you dont use the QNH term in the States. So what do you
call the number you dial up to make the altimeter read airport
elevation?

terry wrote:


I wasnt aware you dont use the QNH term in the States. So what do you
call the number you dial up to make the altimeter read airport
elevation?

altimeter

terry wrote in news:179c2f21-99ad-4415-a9b2-
:

On Apr 18, 12:07*am, Bertie the Bunyip wrote:
terry wrote in news:234756e2-a583-4cbc-8f42-
:

I am confused by this practice commercial nav question. ( at least
I
am confused by the answer in the book which was b. but I think both
a
and c are correct), but I appreciate some other opinions.

Day 1 Altimeter reads elevation of 1390 feet with 1013 HPa set on
subscale
* * * * *( thats equivalent to 29.92 inches of Hg for the US f
olks)
Day 2 Altimeter reads elevation of 1000 feet
Assuming the altimeter subscale was not changed between day 1 and
day
2 it could be said that

a. The QNH is higher on day 2
b. The QNH is lower on day 2
c. The pressure altitude at the airport is lower on day 2
d. *The atmospheric pressure at the aerodrome has not changed.

It's A. It could also be C if the airfield has a serious subsidance
problem.

you are really confusing me now Bertie, I got learned that the
pressure ht was wot your altimeter reads when you have 1013.2 in the
window ( or 29.92 for you ...or maybe not cos everyone knows bunyips
are aussies ) 1000 is lower than 1390 therefore pressure altitude is
lower on day 2.. surely!.


Yer right, of course, I just couldn't resist the joke! There's a name
for that, if I'm not mistaken, and it's QNE. But theyre going for A, I'm
pretty sure and made an error in what thye were trying to say in C. I'm
bi-barometric, BTW.

Bertie

On Apr 18, 1:53*am, Stefan wrote:
WingFlaps schrieb:

QNH means query Newquay Harbour which was the British reference for
sea level.
It should give the atmospheric pressure at that dtaum -but I doubt

You certainly can cite a source for this urban legend?

Urban legend? O, it was not Newquay but Newlyn (both in cornwall). The
datum is sea level as set the British Admiralty back then so the
obvious Q code would have been QNH. Look up the history of the naval
tidal observatory if you don't believe it.

Cheers

On Apr 17, 9:40*am, Gig 601Xl Builder
wrote:
terry wrote:

I wasnt aware you dont use the QNH term in the States. *So what do you
call the number you dial up to make the altimeter read airport
elevation?

altimeter

The Department of Defense uses QNH for altimeter settings in its
forecasts; that replaced ALSTG when the old FT forecast code was
superseded by the TAF code in the late 1970's. Here's the latest TAF
for Offutt AFB:

KOFF 171410 36015G25KT 4800 -RA OVC040 QNH2996INS
TEMPO 1417 35015G35KT 3200 -TSRA OVC025CB
BECMG 1617 03015G25KT 4800 -RA BKN020 OVC040 QNH2997INS
BECMG 0203 36012G18KT 8000 -RA OVC008 QNH2985INS T10/21Z T06/14Z
1415

terry wrote in news:72cae9d8-3bd3-412e-aad5-
:

On Apr 17, 11:29*pm, Stefan wrote:
Larry Dighera schrieb:

*http://en.wikipedia.org/wiki/Mbar

Mbar would be a tad much. You certainly meant mbar.

* What does QNH stand for?
* Atmospheric Pressure (Q) at Nautical Height (aviation)

Bull****. QNH is *not* an acronym. It's one of over hundred Q-Codes
which were defined in the stone age of radio telephony. The letters
were
randomly chosen, think of it as a numeration. Most of those Q-Codes
are
forgotten today, but a few still live. In aviation, I mean in
aviation
in all coutries except the USA, QNH, QFE and QNH are used to define
different altitude settings (roughly spoken).

QNH stands for the pressure you must tune in the kollmans window to
have
the altimeter display the airport elevation when the airplane sits on
the ground. (As opposed to QFE, which ist the pressure to set for the
alitmeter to display zero on the ground and QNE, which is the
altitude
which the alitmeter shows on the ground when it is set to standard
atmosphere.)

For those who believe in Wikipedia:http://en.wikipedia.org/wiki/Q-
code

I wasnt aware you dont use the QNH term in the States. So what do you
call the number you dial up to make the altimeter read airport
elevation?

They don't use any of the Q codes in the US. QNH is one of the few still
in use around the rest of the world, the rest are pretty much archaich.
You stil occasionally hear QFE in the UK, but no airlines I know of are
using it anymore since modern airplanes aren't designed around their use
(QFE settings on the altimeter **** up the computers since the computer
is anticipating a QHN setting to run a bunch of other devices in the
airplane, of which pressurisation is the most relevant) Very
occasionally you hear QSY which is "see you, I'm going to talk to
someone else" and QDM almost never nowadays, but it used to be
relatively common and it's Mag direction to a station. And even less
used QDR which is the Mag radial from a station. I think the Maritime
world might use a lot more of them still, though.

Bertie


Bertie

On Apr 18, 2:40*am, Gig 601Xl Builder
wrote:
terry wrote:

I wasnt aware you dont use the QNH term in the States. *So what do you
call the number you dial up to make the altimeter read airport
elevation?

altimeter

Nope. If you dial up the local barometric pressure the altimeter may
not read airfield elevation....

Cheers