Altimeter settings: QNH versus QFE

[[email protected]]

I have a question for you CFIG's out there: I recently moved to a
"flat" state from a "mountainous" state and noticed that every glider
pilot I have met and flown with in the "flat" state sets his altimeter
to zero (a QFE setting) instead of field elevation. Back in my old
stomping grounds, all my glider friends set field elevation (QNH).

I find this a bit disturbing - even dangerous. It's tough to
deconflict altitude on the radio when you don't know what the other
glider has set his altimeter to!

In response to my questions about why this practice of setting the
altimeter to zero is so common, invariably the response is "that's the
way I was taught" (from both old and new pilots) or that "it's easier
for the student to learn that way" from instructors. Does this mean
that flatland student pilots are mathematically challenged, while those
in mountainous areas are not?

I also hear "it's easier to tell how high up I am when landing". Huh?
What happened to no-altimeter/TLAR patterns? Or are people being
taught rigid altitudes in the pattern?

So - what gives? Is this technique commonly taught? Do instructors
really believe it helps their student? Is it even legal (how do you
get a current altimeter setting during a long flight)?

No prize for figuring out my opinion about this practice...

And please, no tangential discussion about using QFE for IMC approaches
- unless you have two altimeters in your glider...

Kirk
66

[Bill Daniels]

I've found that instructors who teach setting the altimeter to read zero at
field elevation are generally those who have no cross country experience in
either gliders or airplanes and can't grasp the concept of landing at
another location with a different elevation.

I teach setting the altimeter to QNH and how to get an updated altimeter
setting by radio. Complete knowledge of altimetry is required of all pilots
regardless of the aircraft they fly. I also teach TLAR for off-field
landings where the field elevation may be unknown.

BTW, does your altimeter read field elevation before takeoff when set to
local pressure? Most glider altimeters don't and should be calibrated.

bildan

> wrote in message
oups.com...
> I have a question for you CFIG's out there: I recently moved to a
> "flat" state from a "mountainous" state and noticed that every glider
> pilot I have met and flown with in the "flat" state sets his altimeter
> to zero (a QFE setting) instead of field elevation. Back in my old
> stomping grounds, all my glider friends set field elevation (QNH).
>
> I find this a bit disturbing - even dangerous. It's tough to
> deconflict altitude on the radio when you don't know what the other
> glider has set his altimeter to!
>
> In response to my questions about why this practice of setting the
> altimeter to zero is so common, invariably the response is "that's the
> way I was taught" (from both old and new pilots) or that "it's easier
> for the student to learn that way" from instructors. Does this mean
> that flatland student pilots are mathematically challenged, while those
> in mountainous areas are not?
>
> I also hear "it's easier to tell how high up I am when landing". Huh?
> What happened to no-altimeter/TLAR patterns? Or are people being
> taught rigid altitudes in the pattern?
>
> So - what gives? Is this technique commonly taught? Do instructors
> really believe it helps their student? Is it even legal (how do you
> get a current altimeter setting during a long flight)?
>
> No prize for figuring out my opinion about this practice...
>
> And please, no tangential discussion about using QFE for IMC approaches
> - unless you have two altimeters in your glider...
>
> Kirk
> 66
>

[Vaughn Simon]

> wrote in message
oups.com...

> So - what gives? Is this technique commonly taught? Do instructors
> really believe it helps their student? Is it even legal (how do you
> get a current altimeter setting during a long flight)?

I could make an impassioned case for either setting, but 91.121(a)(1)
settles the issue. The altimiter is always set at the current reported
altimeter setting of an appropriate available station or at the elevation of
the departure airport. That is what I have always taught my students.

Of course, here in south Florida the question is pretty academic.

Vaughn

[Papa3]

T o d d P a t t i s t wrote:
> "Vaughn Simon" > wrote:
>
> > I could make an impassioned case for either setting, but 91.121(a)(1)
> >settles the issue.
>
> No it doesn't. 91.121 only requires that the altimeter be
> set to the "reported altimeter setting of a station" when
> the pilot is attempting to "maintain the cruising altitude
> or flight level of that aircraft, as the case may be" A
> glider can't maintain a cruising altitude and is not
> required to do so, so he need not set the altimeter as
> required under 91.121.

Todd,

This may be your "strict" interpretation, but I wonder how the
Federales would react if an incident came up in which the altimeter
setting was a factor. Suppose just for kicks that you barely busted
(say 300 feet) the floor of the Class C airspace at Allentown during a
ridge run and had the misfortune to be doing that just as USAIR Flight
472 was on initial approach to ABE. It was a close call, and the FO
was in a grumpy mood anyway after his 33% pay cut, so he decided to
press the issue and reported the near miss to Approach. Now, for
whatever reason, you happened to land out at Reading, just as the local
DE is finishing up a check flight. He was talking to the home office
before heading out, and somebody mentioned the near miss with a glider
with a big WH painted on the tail.

He gets to chatting with you, and he notices that the altimeter is way
off from the current reported setting at RDG. Starts you down an
interesting line of discussion, no? Given the way things are going,
you can envision 91.13 being invoked.

Anyway, obviously this is stretching it a bit, but the point to me is
that the POTENTIAL downsides of using QFE rather than QNH (which is the
"reported altitude" on all AWOS/ASOS/Weather Observer reports according
to the FAA's own Surface Weather Observing manual) outweigh any
potential pros. I've always taught QNH to students, and I rarely have
anyone who can't do the math after a few flights. If somebody can't
subtract, say, 400 feet from an altimeter showing 1500 feet to figure
out that we're "about" 1100 feet over the home airport, then I wonder
how they're going to handle things like "an approximately 25:1 glide
angle to get home" or to "add half the estimated headwind to the
nominal Best L/D speed".

Just my 0.02,

P3

[Vaughn]

"T o d d P a t t i s t" > wrote in message
...
>> I could make an impassioned case for either setting, but 91.121(a)(1)
>>settles the issue.
>
> No it doesn't. 91.121 only requires that the altimeter be
> set to the "reported altimeter setting of a station" when
> the pilot is attempting to "maintain the cruising altitude
> or flight level of that aircraft, as the case may be" A
> glider can't maintain a cruising altitude and is not
> required to do so, so he need not set the altimeter as
> required under 91.121.

OK, I understand what you are saying, but the sentence starts out with
"Each person operating an aircraft shall..." and by that I assume that they
mean everybody. Further, while you don't maintain a CERTAIN altitude in a
glider, you are supposed to maintain a SAFE altitude and you determine that with
your altimeter.

In short, while your interpretation may fly with the FAA, I would hate to
have my license depending on it.

>
> You didn't list the impassioned arguments you could have
> made, but they boil down to
>
> FIELD ZERO
> 1) you can't hold altitudes in cruise or patterns,
> 2) you're highly likely to land in a field, where you don't
> know field elevation anyway
> 3) it *is* easier for the student landing at his own
> airport.
> 4) Even if you teach using FIELD ELEVATION/91.121, the
> student won't really learn to do the mathematical
> manipulation. Students will just learn to turn base at 500'
> plus field elevation instead of 500' Glider training does
> not usually involve landing at other airports.
>
> FIELD ELEVATION/91.121
> 1) you may land at another airport
> 2) in flight changes easier
> 3) CDAS etc airspace is charted MSL
> 4) your local FAA official gets antsy seeing field zero in a
> glider
> 5) it is really difficult to change over if you learn under
> FIELD ZERO
> 6) when you mix with other gliders from other fields radio
> reports of altitude are not much help to you or them
> 7) most contest pilots do not use FIELD ZERO.

You did a better job there than I would have. Individually, they support
two very convincing, yet opposing, viewpoints.

Vaughn

[Kilo Charlie]

> wrote in message
oups.com...
>I have a question for you CFIG's out there: I recently moved to a
> "flat" state from a "mountainous" state and noticed that every glider
> pilot I have met and flown with in the "flat" state sets his altimeter
> to zero (a QFE setting) instead of field elevation. Back in my old
> stomping grounds, all my glider friends set field elevation (QNH).

Wow....I'm not a CFIG but am one of Kirk's "glider friends in his old
stomping grounds" and for the life of me cannot even believe this discussion
is happening!!!

To do this is an enormous crutch and dangerous for anyone that will ever fly
outside of their local airport environment. How about mountains? How about
large towers there in the "flatlands" where elevations can vary even there
by a few hundred feet making your chart worthless. And as 66 points out,
how about the old "hey I'm in the same area you just said you were in,
what's your altitude?". How about the powered plane that is transitioning
your area and is smart enough to read the chart, see that there is a glider
ops there and makes a radio call to say that he is overflying from the south
at X altitude?

Finally the last but maybe best reason to NOT do this is that when stressed
we all regress to what we were first taught and our natural instincts. If
one of these folks taught on the QFE basis starts taking powered lessons
(God forbid!) or heads to another mountainous glider site and gets in
trouble they are going to revert to thinking in QFE format and that may end
up being a fatal error.

Casey Lenox
KC
Phoenix
(who just got back from Moriarty where it was supposed to be good but
watched it OD for 3 days!)

[BTIZ]

1) we can't turn the altimeter setting enough to set it to zero elevation..
it does not adjust that far
2) how do you stay out of the overlying Class B airspace and ModeC veil
restrictions if you cannot accurately measure altitude above sea level
3) how do you stay out of Class A airspace on a wave or thermal flight (see
#2)
4) how do you know how high you need to be to clear that ridge line ahead or
that you have final glider altitude for that airport that is not home
5) you have some idea of the airport or "ground" elevation you are going to
land on based on reading the contour lines on the chart or airport
information

our field elevation is 2833 and we just spent a weekend at Lone Pine CA,
elev 3680
or maybe Cal City, 2454, or Tehachipe, 4220, and lets not even get started
on the great soaring sites in Utah or Arizona or Colorado.

Best to learn the mental math now.. then later when you travel west for the
first time.

BT

> wrote in message
oups.com...
>I have a question for you CFIG's out there: I recently moved to a
> "flat" state from a "mountainous" state and noticed that every glider
> pilot I have met and flown with in the "flat" state sets his altimeter
> to zero (a QFE setting) instead of field elevation. Back in my old
> stomping grounds, all my glider friends set field elevation (QNH).
>
> I find this a bit disturbing - even dangerous. It's tough to
> deconflict altitude on the radio when you don't know what the other
> glider has set his altimeter to!
>
> In response to my questions about why this practice of setting the
> altimeter to zero is so common, invariably the response is "that's the
> way I was taught" (from both old and new pilots) or that "it's easier
> for the student to learn that way" from instructors. Does this mean
> that flatland student pilots are mathematically challenged, while those
> in mountainous areas are not?
>
> I also hear "it's easier to tell how high up I am when landing". Huh?
> What happened to no-altimeter/TLAR patterns? Or are people being
> taught rigid altitudes in the pattern?
>
> So - what gives? Is this technique commonly taught? Do instructors
> really believe it helps their student? Is it even legal (how do you
> get a current altimeter setting during a long flight)?
>
> No prize for figuring out my opinion about this practice...
>
> And please, no tangential discussion about using QFE for IMC approaches
> - unless you have two altimeters in your glider...
>
> Kirk
> 66
>

[BTIZ]

>>>Is it even legal
>
> Yes.

No

>
>>>(how do you get a current altimeter setting during a long flight)?
>
> You don't.

you do.. you listen to the local ATIS or ASOS or AWOS or check with FSS or
ATC on freq and find out what they are using in the local area

BT

[Stefan]

BTIZ wrote:

> you do.. you listen to the local ATIS or ASOS or AWOS or check with FSS or
> ATC on freq and find out what they are using in the local area

I've yet to see a glider with an accurately calibrated altimeter.

Stefan

[Stefan]

Kilo Charlie wrote:

> How about mountains? How about
> large towers there in the "flatlands" where elevations can vary even there

How about looking out of the window?

Stefan

[Stefan]

I'd like to add that for aerobatic flight, it is common to use QFE, for
obvious reasons. But then, aerobatic flights are usually strictly local.

Stefan

[Bert Willing]

Flying for 10 years over Northern Germany (which, except for the climate,
could be compared to Northern Florida) I always used a QFE setting with the
field 600ft MSL. Airspace regulations weren't that touchy in these days, and
sailplane altimeters aren't that precise anyways so there is just no point
to have it set at 400ft or 600ft. If you rely on judging your altitude by an
altimeter during the pattern for an outlanding, you shouldn't go x-country
in the first place. If you run into a high antenna or a tower on a hillside,
you should think about getting a new prescription for your glasses.

The last 15 years in the mountains are another story though.

--
Bert Willing

ASW20 "TW"


"Stefan" > a écrit dans le message de news:
...
> Kilo Charlie wrote:
>
>> How about mountains? How about large towers there in the "flatlands"
>> where elevations can vary even there
>
> How about looking out of the window?
>
> Stefan

[Paul]

> I've yet to see a glider with an accurately calibrated altimeter.

Strange.
As they are supposed to be certified instruments, they are required to be
checked every two years here in New Zealand. Along with the Transponder and
encoder.
Paul

[[email protected]]

I was taught to fly in meters above ground and do a mental conversion
by multiplying the meters by three and adding 4 500ft to get the real
altitude when speaking to the ATC. I then bought a glider without a
meter altimeter - only a ft one which is set to show altitude above sea
level. No more problem when speaking to ATC but found I was doing
reverse calculations to find out how high I was above the hard stuff.
Then I set my palm up with Soaringpilot which now has a digital terrain
model built in. Now I know exactly how high I am above the ground -
even when I fly cross-country in the mountain regions not far from my
airfield. My LX 5000 computer is set up to show my height above my home
field, which is more important for final glide than anything else.

Clinton Birch
LAK 12

[Robin Birch]

In message >, T o d d P a t t
i s t > writes
>"BTIZ" > wrote:
>
>>Best to learn the mental math now.. then later when you travel west for the
>>first time.
>
>I agree 100%.
It has been really interesting to watch this one. I fly in the UK and
this is what I have been taught to do:

If local then QFE;
if XC then QNH;
If wave flying then QNE once you go above 3,500 QNH (this is transition
round where I am I know it is different in other places). This also
applies XC if you are going near a lot of airspace;

I am taught to land without reference to the altimeter and I don't think
I have ever used it when I carry out field landings.

Not that many glider pilots in the UK have radio licences and a fair
number of gliders do not have radios so the QNH is not generally updated
beyond the departure calculation and setting.

Now, I must say that this is a reworking of what I was taught for power,
not gliding and I can't remember it ever being laid down specifically
what I should do away from local flight other than making sure that I
could land and so on without use of the altimeter.

Cheers

Robin
--
Robin Birch

[Andy]

T o d d P a t t i s t wrote:
It's my understanding that this procedure is also used in
airplanes in the U.K. In the U.S., airplanes will only use
QNH or QNE (above 18,000') and never use QFE.

There is always an exception to any rule. American Airlines used to
always use QFE set altimeter for approach and landing in US. I was
involved in the development of the MD-11. We developed an altimeter
setting system that allowed easy transition between QFE, QNH and STD
for the glass cockpit altimeters. American was the only US operator
that used that customer option. They would land at Denver with
altimeter reading zero after getting QFE setting from local ground ops.
(I was involved in development and flight test, not American's ops, so
any America Airlines pilots on this forum may correct this).

Andy

[BTIZ]

it better be... if the transponder is installed..
BT

"Stefan" > wrote in message
...
> BTIZ wrote:
>
>> you do.. you listen to the local ATIS or ASOS or AWOS or check with FSS
>> or ATC on freq and find out what they are using in the local area
>
> I've yet to see a glider with an accurately calibrated altimeter.
>
> Stefan

[Eric Greenwell]

BTIZ wrote:
> it better be... if the transponder is installed..
> BT
>
> "Stefan" > wrote in message
> ...
>
>>BTIZ wrote:
>>
>>
>>>you do.. you listen to the local ATIS or ASOS or AWOS or check with FSS
>>>or ATC on freq and find out what they are using in the local area
>>
>>I've yet to see a glider with an accurately calibrated altimeter.

When I had my biennial check on my transponder, there was no check of
the altimeter. They did adjust the encoder to read the current pressure
altitude. I know there are strict requirements for encoder and altimeter
accuracy for IFR flight, which requires testing the encoder and
altimeter up to the altitude they will be used in. Is there some
regulation requiring an aircraft with a transponder used in VFR flight
to also have an altimeter calibration? I don't think Mode C is required,
so perhaps the regulation, if there is one, applies only if an encoder
is installed?



--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Kilo Charlie]

I admit to not being up on the current FAR's re altimeters but is there no
regulation for all aircraft in the US to have accurate altimeters?

I would like to think that mine is accurate within a certain limit since as
this discussion points out it is important. No doubt that in the conditions
that we fly in (changing pressure as the day progresses) there is some
inaccuracy but in my experience not more than a hundred feet or so and as
others have pointed out by tuning in to a local ATIS can be corrected.
Those influences are the same for whatever setting you decide to initially
use anyway.

Casey Lenox
KC
Phoenix

[BTIZ]

transponders 91.217, and 91.413

91.413 specify a 24 month check even if used for VFR only for the
transponder to report accurate altitude

AIM 7-2-3, check altimeter against know field elevation and baro setting, if
difference is greater than +/- 75ft from the known elevation. The altimeter
accuracy is suspect and should be reported to a repair station for
evaluation and correction.

The altimeter and transponder must be checked every 24 months for operations
in IFR. (91.411)

That is the only VFR "check" of the altimeter that I have found tonight. But
if the altitude or altitude reporting function (blind encoder) reports
altitude to the transponder, it must be checked every 24 months. If you
don't have a transponder, and you never fly IFR, if the baro setting
displays within 75ft of field elevation. It's "good to go".

BT

"Eric Greenwell" > wrote in message
...
> BTIZ wrote:
>> it better be... if the transponder is installed..
>> BT
>>
>> "Stefan" > wrote in message
>> ...
>>
>>>BTIZ wrote:
>>>
>>>
>>>>you do.. you listen to the local ATIS or ASOS or AWOS or check with FSS
>>>>or ATC on freq and find out what they are using in the local area
>>>
>>>I've yet to see a glider with an accurately calibrated altimeter.
>
> When I had my biennial check on my transponder, there was no check of the
> altimeter. They did adjust the encoder to read the current pressure
> altitude. I know there are strict requirements for encoder and altimeter
> accuracy for IFR flight, which requires testing the encoder and altimeter
> up to the altitude they will be used in. Is there some regulation
> requiring an aircraft with a transponder used in VFR flight to also have
> an altimeter calibration? I don't think Mode C is required, so perhaps the
> regulation, if there is one, applies only if an encoder is installed?
>
>
>
> --
> Change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA

[Nyal Williams]

At 07:30 01 June 2005, Stefan wrote:
>I'd like to add that for aerobatic flight, it is common
>to use QFE, for
>obvious reasons. But then, aerobatic flights are usually
>strictly local.
>
>Stefan
>
Precisely!

And that is the attitude of hundreds of glider pilots
for the last 40 years. Strictly local. I was taught
that way of thinking in a J-3 cub back in 1953, and
then we used it in a glider club in the 60s.

It works fine if you are in an uncomplicated area and
stay local, but it is OLD THINKING! Hardly anyone
travelled to another site those days - even the Cessna
pilots stayed within 25 miles of the home airport (flat
country).

We have a few of those in our club -- guys who never
venture more than 10 miles away in flat land, but the
instructors don't allow it for students.

[Nyal Williams]

I'm surprised at the number of US respondents using
the letters QFE, QNH and that third one, which I have
already forgot. I'm even more surprised that no one
has asked what they mean.


QFE = field elevation
QNH = pressure level indicating altitude above sea
level
Q__ = pressure altitude for a standardized pressure
to use for high altitudes (above 18K in the US)


Now, What does the Q mean?

What are the words for NH and for that other one?

[[email protected]]

For some real fun if you have a large fleet of gliders, go out one
morning and set all the altimeters to 29.92 (or the current setting)
and see how much variation there is in the altitude read outs. You may
be surprised. I certainly was when I did it.

[[email protected]]

Nyal Williams > writes:

....

> QFE = field elevation
> QNH = pressure level indicating altitude above sea
> level
> Q__ = pressure altitude for a standardized pressure
> to use for high altitudes (above 18K in the US)

> Now, What does the Q mean?

They come from morse code days, and there are hundreds of them
covering all sorts of radio, marine, met, and aviation conditions.
Defined by the ITU way back.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

[Tony Verhulst]

wrote:
> For some real fun if you have a large fleet of gliders, go out one
> morning and set all the altimeters to 29.92 (or the current setting)
> and see how much variation there is in the altitude read outs. You may
> be surprised. I certainly was when I did it.


Even more fun, we set QNH of 500 ft. When the student is not looking,
I'll dial in -500 ft. Most don't catch it - the first time.

Tony V.

[Jack]

The original topic is one with some real merit. I learned to fly with
the field = 0. The field was only about 600' MSL so it wasn't a real
big deal, or so I thought at the time. I have just gotten back into
soaring and I am doing my very best to break that habit, and use field
elevation, which for me is now 300 or so. It is taking a while to break
a 19-year habit, but I'm about there. The people that taught me to fly
didn't think they were doing anything wrong. They have nothing to be
ashamed of, that's for sure. I'm proud to say I know all but one of
them... the one that told me I needed to give up, and that I'd never
learn to fly... a real morale builder.

My point is that maybe instructors should be teaching students to add
the field elevation in their decision making. If they're expected to do
that, they will. If you expect them to be stupid, they will. Some have
stated that they don't have a choice because their airports are too
high. They have to teach this the right way. Their students have to
learn this and all do. If I were an instructor, I would not solo a
student that couldn't do this with proficiency. That student will then
know this as instinct, rather than having to unlearn a bad habit. This
is important in our mobile society. I've been moved twice in 8 years. I
expect to move again this coming winter. I am now comfortable using the
MSL field elevation as a start point, and my opinion is that this
should be universal for all students.

Just my nickels worth... and you thought I just had 2 cents...

Jack Womack

[nimbusgb]

Q codes - an exhaustive list - http://www.wemsi.org/qsigs.html

Ian

[[email protected]]

As a newly certified glider pilot, Hurray!!! I am accustomed to using
field zero because this is how I was taught, BUT... I fly in Florida.
Our place is only 200'.
However, the thought of eventually going cross country has me
considering dumbing this QFE setting, but a few complications entered
my mind. Not to mention the accuracy of the instuments in club and
commercial planes. Nothing that simple math can't solve of course, but
nonetheless important when trying to operate with others in the flying
environment.
Examples:
Cloud base reported by other pilots as 4000',what are they determining
that on? QFE or QNH.
Signal to tow pilot to release me at 2000'. I pop off sooner.
Towing out and looking out for the magic 200'mark to turn back to field
in a rope break.
Granted, communication with tow pilot, incorporating the math, and of
course using good old "That looks about right" may solves these
mentioned scenarios, but I just thought, would it not be nice if QNH
was universally used by everyone even if my home field is a measley
little 200'MSL.?

[[email protected]]

First, congrats and welcome to the sport.

Some suggestions per your questions (with the caveat that a discussion
with a CFIG that you trust is undoubtedly a much better source of
guidance!):

The cloud base question gets to the very heart of this issue, however
really only on a theoretical basis - cloud bases have been known to
vary quite a bit, cloud to cloud! And here it gets interesting,
because ceilings are given AGL for the field in question - because
instrument approaches have minimums based on how low the clouds are -
AGL! But cloud heights are given in MSL. Hopefully we aren't in the
situation of shooting an approach to mins in our gliders!

Tows are usually billed in altitude gained on tow - so it's really
difference between takeoff and release altitude. You got to do the
math - but since most pilots seem to like nice even tow numbers (odd,
since the good lift always seems to be at either 900 ft or something
like 1700 ft) it really isn't a demanding calculation to make. Anyway,
just release, and trust me the tow operation will figure out a way to
bill you! Seriously - at a strange field with an odd altitude, just do
the math before hooking up, and when you see that number, you are
there.\\

The "magic" 200 ft - if you still use it, instead of TLAR - is the same
thing, do the math before hooking up as part of your checklist (the E
of CBSIFTCBE, for example) and it will work anywhere.

For those who like a visual reminder, there are moveable "bugs" that
can be attached to the altimeter face that can be set at the field
elevation. Cheap and easy.

Kirk
66