View Full Version : where does "QNH" come from?

go with the flow
7th Aug 2001, 10:07
Okay, okay who wants to be the first to say 'ATIS'(or whatever your local is).
I know it's probably a stupid question but whats the origin of the word/acronym?


Kermit 180
7th Aug 2001, 11:08
Apparently 'Q' codes come from the days of morse code, where the use of standard questions helped to cut down message length. 'Q' therefore stands for question.

Example, 'QDM' would get you a magnetic bearing to a station, QTR would get you the correct time, etc.

QNH stands for what would my altimeter be reading if I were on your airfield above MSL, or the barometric pressure setting at that airfield.

Hope this helps.


[ 07 August 2001: Message edited by: Kermit 180 ]

Nick Figaretto
7th Aug 2001, 11:12
There are probably others on this forum that can answer this question more thoroughly than I can, but still:

The "Q-codes" were originally a whole bunch of three letter codes, starting with Q. This was sort of a "short hand" from the time when morse codes were used to transmit messages. There were LOTS of Q-codes, which all had a different meaning. QNH being one of them, meaning barometric pressure expressed in hPa, corrected for the altitude of the measuring point.

The Q is to destinguish these special three letter codes from other three letter words, since very few (three letter)words start with Q. (Any at all?) (Yes, Quo. ;))

The other two letters? -Don't know if there's any system there at all. And that might even be the point.

Other Q-codes: QDM, QDR, QFE, QTE and QPR. ;)


Cornish Jack
7th Aug 2001, 12:02
Its not an acronym - just an abbreviation to make Morse transmission easier.
Nearly right - The 'Q' code is not, in itself interrogative. To make it into a question rather than a statement it is suffixed by IMI, those three letters being sent as one continuous character (in Morse 'speak', IMI barred)
Without the IMI. it is just a statement i.e. 'the Altimeter setting which will indicate airfield height above sea level' much simpler as QNH :D :D

New Bloke
7th Aug 2001, 13:06
I understood it was “Question Nautical Height” and “Question Field Elevation”.
Is this incorrect?

Vortex what...ouch!
7th Aug 2001, 13:09
Yes they are still, or were until very recently, in use with the military. I learnt morse and various Q & Z codes during my Army signals training. I belive they no longer teach it unless it is required for a specific job.

Essentially the Q and Z codes where 3 letters which correspond to specific sentences or meanings. 3 letters are much easier to send than the full sentence. It therefore goes on that QNH/QFE was used by the RAF when the radio operators used morse and not voice. BT (those in the know will know :D )

Self Loading Freight
7th Aug 2001, 15:05
Q codes are still used by radio hams, although the requirement to know morse code is being downgraded and will probably vanish over the next few years and thus the Q codes will most likely fade away too. (But this brings us into the world of ham radio politics, which is frighteningly unpleasant).


7th Aug 2001, 15:19
Wags will tell you QNH stands for "Queer Notation of Height".

7th Aug 2001, 15:50
Questioning Never Hurts...

7th Aug 2001, 19:00
Talking about QNH, QNE, QFE...

I did my basic training in the States and when I came back to Europe I was really astonished by the fact how our authorities are dealing with simple stuff (in the states it was simple) :confused: :confused: . Standard (QNE) setting only above FL180, so all the G/A-guys don't have to worry about transition alt/level!

Can anyone explain why we don't do it the same way here in Europe? :rolleyes:

Who is using QFE (apart from maybe some aerobatic pilots)? :confused:

7th Aug 2001, 19:07
QNH "Normal Home"

QNE "Normal Enroute"

QFE "Field Elevation"

7th Aug 2001, 22:25
Moscow uses QFE. Thanks to the Jepp plates, it's not as difficult as it could be.

7th Aug 2001, 22:46
A Spam mate doing an exchange tour here told us that they consider 'QFE' stands for 'Queer F*cking English'!!

Nick Figaretto
8th Aug 2001, 05:02
Akro: I fly Turbo-Prop, in Europe and we often fly pretty long sectors below FL180. (Especially when there's strong headwind.) Wouldn't you have to change QNH "all the time" to make sure you have the same reference as other traffic if the TA is 18 000 ft?


8th Aug 2001, 05:30
I too thought that anything prefixed with Q meant question. I have since been told that the Q is Latin for Quasi, meaning 'about'.
ie QNH = quasi nil height, about nil height.

He was a wise old man, so I kind of believed him...... he could also be wrong.

go with the flow
8th Aug 2001, 07:03
Quod Erat Demonstrandum??? ;)

Thanks all.

8th Aug 2001, 13:20
For the bored or interested, officially, they are contained in Appendix 9 to the Radio Regulations Annex to the International Telecommunications Convention (Atlantic City) 1947, for blocks QRA to QUZ inclusive, and in ICAO publications Dec 6100-COM/504/1 for blocks QAA to QNZ inclusive.

Radio hams could probably tell you a lot more about them, but there are a few interesting ones, like "QUQ - Shall I train my searchlight nearly vertical on a cloud, occulting if possible and, if your aircraft is seen, deflect the beam upwind and on the water (or land) to facilitate your landing?" :D

8th Aug 2001, 14:44
Hi Nick F.,

Of course you would have to change alt setting from time to time (not really all the time, depends on the weather as well)! However, as we were flying under so called "flight following" all the time (another neat service you get from ATC in the states as well -> just another huge topic that works much better over there), they always gave us the alt setting for the area we were flying in! When you enter a new sector the new controler automatically gives you the new alt setting.

Who else is using QFE apart from Moscow?
(I heard also that Alitalia is using QFE for their approaches? It might be just a rumour though.)
Any help is appreciated!

Don D Cake
8th Aug 2001, 15:27
Q codes were my downfall when I trained to be a ship's radio officer. There were over three hundred to learn and I'm afraid I gave up :(

I believe they evolved from the Post Office telegraphy two letter codes, when sending Morse code you abbreviate as much as possible. Experienced WT operators would even abbreviate numbers if sending a lot of them ie 1 (.----) would become .- 2 (..---) would become ..- etc. The codes were prefixed by "Q" to make them more obvious, when you heard the letter "Q" you automatically expected a Q code. There have also been Z codes and X codes. All these letters are rarely used in text so they stand out. For most of the codes there is no logic or rationale although it may not be a coincidence that QRS means send more slowly and QRQ means send more quickly. Assigning a "meaning" to the codes just makes them easier to learn. Q has certainly nothing to do with question, a Q code is made into a question by suffixing it with a question mark eg QRL? - are you busy?; QRL - I am busy.


8th Aug 2001, 15:48
he answer to QNH.
Plenty of people have talked about the origin of 'Q' so I'll go no further. As to 'NH' you need to think about sea level. As QNH give you your height abouve sea level (we call it altitude)we need a reference datum. Mean sea level is taken from a measurement point in Cornwall - Newlyn harbour infact. Therefore the NH is derived from Newlyn Height.

8th Aug 2001, 15:57

I don't know if I believe it myself but I read that it has to do with the high mountains (compared to most areas in Europne) in the US. Altitude until well above all that cumulogranitus, FLs after that.

Personally, I find what Nick is saying more believable. :) Hmm, I can imagine that sectors (in this case significant as areas with the same QNH) tend to be larger in the US as well, making HOVs and flying on altitude less of a PITA?

Any other suggestions?


8th Aug 2001, 18:28

Sounds like a good reason even though I don't really believe it myself since I come from Switzerland (and as you might know we've got some high "cumulusgranitus" around as well). Here same rule applies as in the rest of Europe (at least AFAIK). So there must be another "good" reason why we do it like this over here (unless the yankees are really smarter :D ).

Air Conditioned
10th Aug 2001, 07:29
'Q' was probably only used to be distinctive, with no real meaning, any more than the military used 'Z'. I doubt very much that many of the code groups were ever self evident, but of course after the event you can dream up anything to fit. Q codes were not just questions since the meaning could change between transmission and reply, one meaning "Am I...?" and the other "You are..." or "What is?" and the appropriate reply would be prefixed the same. IE QDM - "What is my bearing" and "Your bearing is...." and no doubts about whether it is from/to, magnetic or true, Spanish or French etc, etc.

Such code forms were, and may still be, necessary to ensure quick and umambiguous interpretation of critical information. The use of the word 'altimeter' (not uncommon in the 'States) is a hazard if the recipient doesn't know if it really means QNH, QNE, or QFE and transmitted between persons without a common natural language. There were also several other Q,s for altimeter. The use of Q code is clear, easily used and unambiguous.

Q code was not limited to W/T nor three letters. Teletype time was much improved and clarified by the same form. NOTAM code was (is?) Q and came in five letter groups. This may illustrate the point, since a single group could explain the whole NOTAM irrespective of the language it was decoded in. I can't recall any proper code groups, typically something like QNBOS might mean Q-(use the Q book), NB-(NDB) OS-(out of service), and would do so in English, Russian, Chinese or anything else. Some two-letter encodes were self evident but most were not.

Not everything the Ancients did was stoopid.

11th Aug 2001, 18:16
This one comes round on PPRuNe from time to time and even receives some interesting answers. There was a thread on Tech Log back in July 1999 which is worth reading:

The Q things (http://www.pprune.org/cgibin/ultimatebb.cgi?ubb=get_topic&f=3&t=000300)

Hope this helps, go with the flow.

Mister Geezer
11th Aug 2001, 18:40
I have been told on good authority that the NH stands for 'Nautical Height'.

ATC only measure QFE. QNH a calculated figure.

In otherwords ATC know the airfield pressure setting (QFE) and due to the known elevation of the airfield above sea level they can calculate the QNH by subtracting the known difference from the QNH to arrive at the QFE figure.


11th Aug 2001, 18:52

Everybody knows that QNH comes from ATC (to be quite correct from The Met Office.

See. That's that cleared up!!!

12th Aug 2001, 23:04
Just to add to all these, does any country use QDR and QDM for tracking. ATC in my country for non radar environment aerodrome uses these q codes. They usually will ask us to track on the QDR of a navaid. The misconception here is that it is assumed that a QDR is the radial inbound to the navaid when in fact a QDR is a bearing to the station no matter where you are heading and the QDM is the heading to steer in nil wind to the station. Can anyone enlighten me on this.

Nick Figaretto
13th Aug 2001, 11:37
...a QDR is a bearing to the station no matter where you are heading :confused:

The QDR is the magnetic bearing from the station. A QDR from an NDB is "the same as" a radial form a VOR. A QDM to an NDB is "the same as" an inbound course to a VOR.

The track (or "position") of QDR 190 is exactly the same as QDM 010.

And, as you say, this is irrespective of the aircraft's heading or direction of flight, but it applies both for QDMs and QDRs.


PPRuNe Radar
13th Aug 2001, 19:21
There is a pretty definitive listing of Q codes here.



Don't fall into the trap of thinking that QNE is the Standard setting of 1013.2 or 29.92. QNE is the indication (in feet or metres) which will be shown on your altimeter at an airfield when that pressure is set. You won't find many airfields above 18,000' to land at to try it out, even in the US ;)

[ 13 August 2001: Message edited by: PPRuNe Radar ]

15th Aug 2001, 15:26
I think these were dialogues rather than values.


Aeroplane Radio Operator "QNE LHR 1230" (= What will the altimeter reading be for London at 12:30 if 1013.2 is set?)

ATC "QNE LHR 128 FT" (= The altimeter reading for London at 12:30 will be 128 feet)

15th Aug 2001, 16:53
I have made a cursory search of the grey matter and I brought up some long time (and somewhat vague) memories on ATPL groundschool
on transition levels/altitudes. Are they not based on an altitude that clears all obstacles within the prescribed area by a minimum amount(formula used, min clearance increased with height of terrain), and are therefore terrain dependent?
When the formula is applied, it gives the maximum number of available flight levels as governed by terrain limitations.
On the other hand, it's been so long I might be mixing it up with something else.

7th Sep 2001, 09:50
In the USA, "altimeter setting" always means QNH. Inches are always used. Above 17,500, altimeters are always set to 29.92 inches. QFE used to be used by Eastern and American Airlines, and they would get their QFE from their company radio, since the ATC facilities didn't even have it available. Even on approach, they kept a third altimiter set to QNH. Most pilots in the USA don't know the meaning of QNH or QFE, etc., since we don't use the three letter Q codes. The 5 letter ones are used in NOTAMS, which in our politically correct times are referred to as NOTACS (C is for crew).
By the way, ATIS means Airport Terminal Information Service.

8th Sep 2001, 02:04

The "Q" in "Q" code stands for "QUEEN'S


[ 07 September 2001: Message edited by: TR3 ]