QNH
 

What exactly does this acronym stand for and where did it originate?

It stands for "Question Nil Height"

Used back in the days when morse code was used. They would ask for QNH through morse code, and get the atmospheric pressure at sea level.

Im sure someone will have more to add, but thats the basics of what it means.

QNH
 

http://www.kloth.net/radio/qcodes.php

This should answer the question. Good for the boaty floaty gang too.

It's not an acronym, or an abbreviation, but just one of a whole host of three-letter codes in the Q-Code system. I think Aussie's answer is simply the result of somebody finding some words that fit - almost. After all, QNH has nothing to do with height.

The system originated in the days of morse code, where a simple three-letter code could replace perhaps a lengthy sentence, and save a lot of time. It also meant the message could be understood instantly, in any language, and without any ambiguity.

I'm guessing it's a Q code because there are no three-letter English words that begin with Q, so as soon as one is received it is obvious that it has a special meaning.

The Q certainly stands for Question, but I was under the impression that NH was for Nautical Heightm afterall it is an elevation above sea level that QNH represents............... incoming??

Farmer1 has it bang on.

The Q "codes" are exactly that - codes. I've had a protracted discussion with a non-comms (in the radio operator sense) colleague who had it as an acronym in some safety docs a few months ago. I eventually managed to get it correctly descibed in the glossary that was in the document he was scribing.

Pedantic to the end .... :ouch:

ST

Query/Question Newlyn Height
 

Feel free to correct me anyone if this is wrong.

I was told that QNH stands for QUESTION/QUERY NEWLYN HEIGHT.

The original sea level pressure in the UK was always based on the pressure at Newlyn in Cornwall. The OS (Ordanance Survey) website defines ODN (which defines the height of any point in the UK) as Ordanance Datumn Newlyn. ODN is used as defined in the following quote from the OS website.

This is our national coordinate system for heights above mean sea level (orthometric heights). It was originally based on tide gauge readings at Newlyn, Cornwall. ODN is the usual definition of height above mean sea level in mainland Britain and some islands.



Newlyn is the home of the UK National tidal centre.
And historically is where UK National sea level pressure is defined from.

And before anyone says QNH is an altitude, a QNH pressure setting defines your altitude or height above mean sea level. So by flying on a QNH you are flying a height (altitude if refering to it correctly on the RT) above MSL. Just as you would be flying a height agl if using a QFE.

I have read various accounts in books and the internet as to which came first QNH or Question/Query Newlyn Height.
By this I mean is QNH an acronym or is Question Newlyn Height a useful pneumonic for QNH.
If anyone knows the answer please tell me.

This could all be a load of tosh, but never heard a better explanation or had it dissproved.

CMO

Then there is QFE which is the pressure setting to apply to your altimeter to result in close to zero altitude indicated at the airfield datum.

The closest I can get to unscrambling QFE as though it is an acronym is Quick Find Earth!!

Airfield datum begs the question. Where normally is the airfield datum particularly in relation to the nominal GPS position or INS setting.

What other Qs relate to atmospheric pressure. I've forgotten because I don't think they matter much or have become obsolete.

QFE is Question/Query Field Elevation

In the Wikipedia at http://www.answers.com/main/ntquery;...a&linktext=QNH
See also http://www.answers.com/topic/q-code

<<What other Qs relate to atmospheric pressure.>>

Well there's QNE for high altitude airports.. My brain cells are long dead but I think it's used at places where it would not be possible to unwind the altimeter to read the QNH. It's where you set the altimeter to a particluar (standard?) setting and you're told the altitude it will read on touch down.. Someone please confirm.

Have those who are trying to fit words to the codes read the initial link by albatross?

There may be well known mnemonics to aid memory of often used codes - and possibly even assisted in their initial allocation, but essentially the codes came before the widely used 'memory aids' - one only has to look at the number of them to seee that they cannot all stand for something.
Possibly those who only hear QHN/QFE don't realise the number of others and assume those two must have a meaning.

Even today - in the ATPL we have (including mnemonics I was taught):
QDM: Mag heading to [Direct Magnetic]
QDR: Mag Bearing from [Direct Radial]
QTE: True bearing from [True Eminanting (from)]
QUJ: True track to [True to the flag (Union Jack - starting to reach a bit I know!)]

And I have certainly used:
QSY: Leaving frequency (normally with mil controllers)
QGH: According to the link it is simply asking for clearance to use an approach - I was under the impression it was itself a specific type of approach where ATC homes in on your tranmission (instead or RADAR) and talks you down. Done a few (with real RADAR backup - I may be stupid but I'm not suicidal!)

Edited:

HD, from albatrosses link:
QNE: What indication will my altimeter give on landing at ... (place) at ... hours, my sub-scale being set to 1013.2 millibars (29.92 inches)?

On landing at ... (place) at ... hours, with your sub-scale being set to 1013.2 millibars (29.92 inches), your altimeter will indicate ... (figures and units).

Just to repeat ....
'Q' codes ARE NOT MNEMONICS - they are a series of three letter combinations which were, initially, used in W/T (morse code) transmissions to aid international understanding and for brevity. For military use there was also the 'Z' code which operated similarly. The 'Q' had no query significance, it was just a common starting letter. If the code was used as a query, rather than a statement, it preceded the additional 'code' IMI (sent as one continuous character). The equivalent interrogative for the 'Z' code was INT.
Their continuing use in R/T is indicative of their universality.

Re QNE
 

To set QNE is to set the standard pressure setting of 1013hpa - ie when passing the transition altitude. It would never be used for landing unless the QNH (or QFE if used) just happened to be 1013.

Apollo 100 - incorrect I'm afraid

QNE is NOT 1013mb - that is the Standard Altimeter Setting

QNE IS (As HD says) occasionaly used at High Altitude Airports and is the level indicated on an altimeter, on the ground at that location, when 1013 is set.

It's a common misunderstanding which does keep cropping up however.

:ugh:
Do I not dislike altimeter questions?

QNE is 1013 millibars. Set at transition level and reset at transition altitude.
All aircraft with 1013 set will indicate a flight level which is then a standard for all aircraft with 1013 so set.

QFE is that setting which will allow the altimeter to read 0ft at the touchdown reference point. It was much favoured by the military and is still in use.
Therefore, go around height might be at 200ft, altimeter reading.

QNH is the setting which will allow the altimeter to read airfield elevation at the touchdown reference point.
It is used at high airfields such as Johannesburg where it is not possible to wind down the altimeter sufficiently to allow 0ft to be read on touchdown.
Therefore go around height might be at 5,780ft, altimeter reading.

Does that help muddy the waters?:D

MATS Pt 1 App 'A' page 2 gives QNE values and an explanation of their use.

Not quite, I don't think, Chilli. I don't think it has anything to do with the airport's elevation, but the pressure. If the QNH is outside the range of the altimeter's setting, then that is when QNE is used.

We used to use it offshore, which is not a place noted for its high elevations. The radio op would have two altimeters - one set to give QFE, and the other with the adjustment inhibited, and set to 1013. He would give us QFE and QNE. We would set QFE on one altimeter and 1013 on the other, and confirm the QNE. The simple process checked all four altimeters as well as the radio op and the pilots.

Dead simple, and absolutely foolproof.



Except:

I paid a visit to the radio room once, and an aircraft called. The radio op gave the QFE, and then consulted a chart before giving the QNE.

There had never been a second altimeter, and someone in the dark and distant past had produced the QNE chart. The radio op was more than a bit upset when I tore up the chart, because he would no longer be able to provide the QNE. No amount of explanation on my part could make him understand how dangerous his practice could be.

The QNE is set when altimeters cannot be set to other pressures. La Paz in Bolivia is, I believe, a classic example of where it is used.

Farmer1.... Why would QNE be used offshore instead of QNH as it complicates matters? The pressure on the surface rarely becomes so high or low that it would be outside the subscale of most altimeters.

HD,

Because it enables you to check the accuracy of the altimeter in the radio room, and also the radio op. Bear in mind he is a radio op, not an ATCO, and at one time did not need any experience or instruction in aviation matters in order to get the job. I remember one who had never heard of the term QFE, for instance, and was told of another who was busy looking in a drawer for said item.

QFE is universally used, QNE was supposed to be a safety bonus.

A question for you: Can you explain why La Paz cannot use QNH?