QNH, QNE, QNF Altimeter Settings

[Richie2]

I understand the definitions of:

QNH — The barometric pressure as reported by a particular station (local altimeter setting)

QNE — Pressure Altitude (29.92 or 1013.2 mb/hPa)

QFE — Altimeter setting referenced to airport field elevation (where field elevation equals zero feet)

BUT…

What do the actual letters stand for and where did they come from?

That is:

Q = ?

N = ?

H = ?

F = ?

E = ?

Thanks

[barnaby]

God only knows! I think that they are an old military Q coding system. I don't think that the letters have any particular meaning.

Your definitions are not quite right though.

QFE - Presseure measured at the station

QNH - QFE mathmatically reduced/increased to sea level using ISA std figures

QFF - QFE mathmatically reduced/increased to sea level using actual conditions (temperature)

QNE - Emergency pressure setting used for low pressure/high altitude operations. I.E. when the actual pressure setting is off the scale of the altimeter.

Hope this helps,
Barnaby

[Capt Wannabe]

Sorry to be a bit pedantic, but QNE is not in fact an altimeter setting.
QNE is the elevation of the airfield (threshold?) when 1013.2 is set on the altimeter.

[Captain Stable]

wrt the Q-code, barnaby is quite correct.

The Q- (and Z-) codes were developed merely to provide speed and clarity when much aviation communication was in Morse.

Since then, no doubt in an attempt to try to provide mnemonics or reminders, people have tried to assign meanings to the separate letters, but they are not "official".

[pilot007]

QFE - Queens Field Elevation

[spekesoftly]

Capt Wannabe,

Sorry to be even more pedantic, but:- "QNE is the reading in feet on an altimeter with the sub-scale set to 1013.2 mb when the aircraft is at aerodrome or touchdown elevation."

This will not give airfield elevation - setting Airfield QNH on the sub-scale will.

[Captain Airclues]

www.kloth.net/radio/qcodes

[Captain Stable]

People have often wondered what the "Q", "X", "n...." stand for in the Q-codes.

Simple answer is that they don't stand for anything. Many people have made up anagrams, acronyms, mnemonics and limericks to explain them - but they ain't official.

[Spitoon]

spekesoftly, sorry to be even more pedantic.

It won't necessarily be in feet. ;)

[Bright-Ling]

and to be extra super pedantic...


....it might 29.92 inches, not mbs!

[fireflybob]

Well of course the UK has to have their QFE!

In the USA where only QNH is used they call it "The Altimeter Setting".

[parris50]

Err... to be super super pedantic don't we have to say "hectopascals" now?

[BDiONU]

To confirm earlier answers the 'Q' is indeed a wartime code (second world war!). Other examples are QTE = True bearing from base. QDM = Magnetic heading for base. And, still heard often (relatively) QSY = going to en-route frequency.

[NW1]

Capt W is absolutely correct:"QNE is the reading in feet on an altimeter with the sub-scale set to 1013.2 mb when the aircraft is at aerodrome or touchdown elevation"You are right in that the altimeter will not give airfield elevation, but in this case that is not what is required - it will give the airfield's pressure altitude or QNE (pressure altitude is the height above the 1013.2mb level - and airfield pressure altitude rather than altitude amsl is the definition of QNE).

QNE is the "odd man out" amongst these "Q" codes in that it is measured in distance units rather than pressure units. It is a common mistake to confuse QNE with the standard pressure setting of 1013.2mbs / 29.92"Hg. The latter is a sub-scale setting, the former is an altimeter reading on the airfield with standard (rather than QNH or QFE) set.

I've still got an old copy taken from a 1955 Manual of Air Traffic Services with a comprehensive list of the old "Q" codes. They had fun in the days of w/t - if you sent "QRL" it meant "I am busy - please do not interfere". How things change..........

[PS: The UK has a filed difference to use millibars in place of hectopascals - a bit of a waste of breath as the two units are identical]

[middlepath]

What the hell with this Q business, could not we do something simple for average pilot a more userfriendly terminology so that no none inadvertantly make error.

[spekesoftly]

NW1,

Had Capt W said pressure altitude instead of elevation - then I suggest he would have been absolutely correct.

You appear to attribute the quoted definition of QNE, at the beginning of your post, to Capt W. If you agree with the definition, then credit where it's due, please! ;)

[NW1]

ah... see what you mean. All too subtle for me - who said what to whom etc.. must try harder!

Thank goodness these "Q" codes are all but gone - they were designed for w/t anyway so they're not even employed in the job they were designed to do - no wonder they're so confusing!

QSY

[WHBM]

I think we all understand what they mean nowadays (at least I hope so!), but I understand the actual origin was as follows:

Q codes were developed in the old W/T morse days to shorten the message. Q was chosen as the prefix because so few "normal" words began with Q, so it alerted the radio operator to a 2-letter code coming.

QNH = Q Notional Height
QFE = Q Field Elevation

... as explained to me long ago and far away by my father, WW2 Halifax crew.

The Americans don't use QFE because in Colorado, etc, where all the fields are at 5,000 ft-plus, you cannot wind the subscale on the alti down low enough to get a QFE.

[Flying is the Pitts]

Hey my first ever posting!

I think QNH- is the Q code, where NH = Nautical Height
and QFE- is the Q code, where FE = Field Elevation.

Some others QDM - Direction Magnetic to the station

QDR - Direction Radial from the station.

Also QSY, I've heard a few of the yankee boys requesting "QSY to 121.0" In other words a request to change frequency.

Best regards,

Chuck Yeager