Altimeter Question

On Apr 18, 7:10*am, Stefan wrote:
WingFlaps schrieb:

Perhap we are at crossed purposes but an ARFOR does not refer to an
airfield -that's a METAR and not all fields issue them. So in this
case how can QNH give field elevation unless it's an ISA day?

Again: QNH gives *by definition* the field elevation. If an ARFOR gives
you a QNH, then it is related to one well defined spot on the surface.


As I understand it ( In Australia) the QNH in an ARFOR must be within
5 mbar of the "real QNH" - ie what gives you field elevation for any
place within that area. otherwise the area will be broken up into sub
areas and no 2 adjacant sub areas must differ by more than 5 mbar.
That way the errors which Wing flap alludes to, and must certainly
exist in non ISA atmosphere, would result in errors of no more than
150 feet between aircraft using either the correct AFROR QNH or the
airfield set QNH

terry wrote in
:

On Apr 18, 3:33*am, "Barry" wrote:
Actually, there are a lot of anomolies around the world. Eastern
Europe and Russia doggedly cling to using windspeed in
Meters/second and have reluctantly accepted using feet for
altitude, though there are still a lot of published platform
altitudes of something like "2746 feet"

I learned to fly in France in the 1980s and they used a weird
combination
of
feet and meters. *Altimeters read in feet,and minimum safe altitudes
wer
e
charted in feet. *But charted obstructions and airspace restrictions
wer
e in
meters. *Everyone set QFE (altimeter reads zero on the ground) for
takeo
ff,
then reset the altimeter to QNH if leaving the traffic pattern.
*Flight
levels
began at 3500 feet.

Can any Europeans out there tell me if it's still like that?


Its still like that in australia, we use feet for altitude , but we
use meters for horizontal distance. OurVFR rules are to stay clear of
cloud by 1000 feet vertically and 1500 m horizontally. Hpa for
pressure except tire pressure which is psi


Meters is the international standard for vis, except in the US!

Bertie

Stefan wrote in news:c9458$4807bcae$54487328$4551
@news.hispeed.ch:

WingFlaps schrieb:

Perhap we are at crossed purposes but an ARFOR does not refer to an
airfield -that's a METAR and not all fields issue them. So in this
case how can QNH give field elevation unless it's an ISA day?

Again: QNH gives *by definition* the field elevation.

Only at the airport ref point, so, no, it doesn't.


Bertie

terry wrote in news:375462b0-66e7-4ed0-b45d-
:

On Apr 18, 7:10*am, Stefan wrote:
WingFlaps schrieb:

Perhap we are at crossed purposes but an ARFOR does not refer to an
airfield -that's a METAR and not all fields issue them. So in this
case how can QNH give field elevation unless it's an ISA day?

Again: QNH gives *by definition* the field elevation. If an ARFOR
gives
you a QNH, then it is related to one well defined spot on the
surface.


As I understand it ( In Australia) the QNH in an ARFOR must be within
5 mbar of the "real QNH" - ie what gives you field elevation for any
place within that area. otherwise the area will be broken up into sub
areas and no 2 adjacant sub areas must differ by more than 5 mbar.
That way the errors which Wing flap alludes to, and must certainly
exist in non ISA atmosphere, would result in errors of no more than
150 feet between aircraft using either the correct AFROR QNH or the
airfield set QNH




Yipes! Are you studying to be an astronaut?

Bertie

Barry wrote:
. Everyone set QFE (altimeter reads zero on the ground) for takeoff,
then reset the altimeter to QNH if leaving the traffic pattern. Flight levels
began at 3500 feet.


Wouldn't that be impossible to do at high altitude airports, such as in the
Alps?

John Galban=====N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums...ation/200804/1

Its still like that in australia, we use feet for altitude , but we
use meters for horizontal distance. OurVFR rules are to stay clear of
cloud by 1000 feet vertically and 1500 m horizontally.

Are obstruction elevations (towers, mountain tops) charted in feet or meters?
In France they were in meters, which I thought was pretty stupid given that
the altimeters were in feet. VFR cloud clearance requirements, both
horizontal and vertical, were stated in meters.

"JGalban via AviationKB.com" u32749@uwe wrote in
news:82d6098e5626c@uwe:

Barry wrote:
. Everyone set QFE (altimeter reads zero on the ground) for takeoff,
then reset the altimeter to QNH if leaving the traffic pattern.
Flight levels began at 3500 feet.


Wouldn't that be impossible to do at high altitude airports, such as
in the
Alps?


What happens is that the transition level is localised. they're usually
between 3,000 and 5,000 above the local terrain, though that depends on
airspace divisions around the area and local state views and traditions.
Usually you can expect to transition around 4-5 thou above the airport
going up. In mountainous areas, minimu flight levels are dictated by the
QNH and temperature. The US is the only country I know of that has a
nationwide transition as high as 180.


Bertie

Bertie

On Apr 18, 9:10*am, Stefan wrote:
WingFlaps schrieb:

Perhap we are at crossed purposes but an ARFOR does not refer to an
airfield -that's a METAR and not all fields issue them. So in this
case how can QNH give field elevation unless it's an ISA day?

Again: QNH gives *by definition* the field elevation. If an ARFOR gives
you a QNH, then it is related to one well defined spot on the surface.

BINGO! That's right, setting QNH on an altimeter DOES NOT does give
field elevation UNLESS it's issued for that field :-)

Cheers

On Apr 18, 10:02*am, terry wrote:
On Apr 18, 7:10*am, Stefan wrote:

WingFlaps schrieb:

Perhap we are at crossed purposes but an ARFOR does not refer to an
airfield -that's a METAR and not all fields issue them. So in this
case how can QNH give field elevation unless it's an ISA day?

Again: QNH gives *by definition* the field elevation. If an ARFOR gives
you a QNH, then it is related to one well defined spot on the surface.

As I understand it ( In Australia) the QNH in an ARFOR must be within
5 mbar of the "real QNH" *- ie what gives you field elevation for any
place within that area. otherwise the area will be broken up into sub
areas and no 2 adjacant sub areas must differ by more than 5 mbar.
That way the errors which Wing flap alludes to, and must certainly
exist in non ISA atmosphere, would result in errors of no more than
150 feet between aircraft using either the correct AFROR QNH or the
airfield set QNH

Yep. Altough I think I've seen pretty big local QNH changes without
the ARFOR areas being broken up but I can't recall them being bigger
than 5hPa.

Cheers

On Apr 18, 11:04*am, Bertie the Bunyip wrote:
Stefan wrote in news:c9458$4807bcae$54487328$4551
@news.hispeed.ch:

WingFlaps schrieb:

Perhap we are at crossed purposes but an ARFOR does not refer to an
airfield -that's a METAR and not all fields issue them. So in this
case how can QNH give field elevation unless it's an ISA day?

Again: QNH gives *by definition* the field elevation.

Only at the airport ref point, so, no, it doesn't.

He'll get it in the end... high to low look out below! I'll guess he's
not flown Xcountry to non ATIS fields?

Cheers