Altimeter Question

On Apr 18, 7:55*am, Stefan wrote:
WingFlaps schrieb:

So an altimeter set to local QNH will always read field elevation *by
definition*.
Yes it may say that but it's being loose because it forgt to include
the "barometric pressure reduced to MSL by application of the ISA".
Alltimeters are calibrated for the standard atmosphere. -right?

Right.

Think about it, if an ARFOR gives QNH how could it be correct for all
terrain if local temperatures differed? *I covered this in my PPL tech
course -was this not covered in your manuals?

Think about it, nobody said it would be correct for all altitudes, but
just for one altitude: the airfield elevation.



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?

Cheers

Cheers

Cheers

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.

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 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

On Apr 18, 9:05Â*am, Bertie the Bunyip wrote:
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" Â*- 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?

Are there any openings?

terry wrote in news:ea7c4c43-ffdf-4802-825b-
:

On Apr 18, 9:05Â*am, Bertie the Bunyip wrote:
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" Â*- ie what gives you field elevation for
a
ny
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?

Are there any openings?


Sure! Lots of applicants though.

Bertie

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

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

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

WingFlaps wrote in
:

On Apr 18, 11:04*am, Bertie the Bunyip wrote:
Stefan wrote in
news:c9458$4807bcae$54487328$455
1
@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?


I doubt he flies at all.


Bertie