Qnh, Qfe, Qdm.....?

[henrypottinger]

Can someone shine some light on the history of these acronym's?
I believe they stem from morse code days asking conditions of
runways/airports etc...more details please?
(E.G. If QDM is Question Direction Magnetic, what are the rest?)
Cheers in advance to those in the know....

[Diaz]

http://en.wikipedia.org/wiki/Q_code

[Mr.Buzzy]

Direction Finding

QDM
Magnetic heading TO a station
QDR
Magnetic heading FROM a station
QUJ
True bearing TO a station
QTE
True bearing FROM a station
QFU
The Runway in use

So why do people call the localizer bearing QDM when QDM is a heading?

[OPEN DES]

Wikipedia is wrong.

They are both bearings.

[luddite]

Doesn't QBT mean 'I am about to wind in my aerial'?
Or am I showing my age? :ooh:

[P.Pilcher]

" When QBI conditions are declared for Croydon, only one aircraft is permitted to enter the zone at one time. The aircraft proceeds towards the aerodrome receiving guidance from the controller. He signals 'Motors North', or 'Motors South' e.t.c as appropriate. The pilot thus modifies his heading until the signal 'Motors Overhead' is received. The pilot then turns downwind, and after an appropriate time, turns through 180 degrees. He then commences a letdown at an appropriate rate allowing for wind conditions to be able to land at the aerodrome. Pilots rarely attempt such a manoeuvre with a cloudbase less than 100 feet."
I quote this roughly from an aeronautical encyclopedia of about 1938 which gives full details of the operation of the Short-Mayo composite amongst other things.

Anybody fancy landing their 747 this way on the grass at Croydon with a 100' cloudbase? I assume that the legendary Capt. O.P. Jones of Imperial Airways did this in his HP 42 every day!

P.P.

[old,not bold]

Is my memory correct that in the days when men were men and ATC Controllers knew their stuff, a QGH approach involved the Controller calling for a series of transmissions which, seen on his VDF equipment as QDMs, enabled him to give a series of heading and descent instructions to place one on the glidepath.

He would bring you overhead, and then outbound on the runway reciprocal, as I remember it, descending from 2000' to 1000' on the QFE, then a level procedure 180 degree turn, then a further descent on the glidepath until you saw the runway (or, presumably, reached the MDA, or hit the ground).

It would have been the Controller-controlled version of a VDF approach, I guess, in which the pilot calls for successive QDMs, or was it QDRs. I've still got my little plastic VDF approach cheat wheel.

Or something like that; I think I've missed some important details.

The Q denoted a whole series of codes used with key transmissions which stuck, when voice took over, as a simple clear shorthand that everyone understood and still does, mostly.

There was a story that the legendary Sywell controller (early 1960s) could handle 9 aircraft simultaneously on QGHs.

[Mike744]

The Q Code I particularly remember from my time as a marine radio officer was:
QUQ Shall I train my searchlight nearly vertical on a cloud, and if your aircraft is seen, deflect the beam up wind and on the water?

[old,not bold]

PS

There's also a Q code for "put a competent operator on the set", used to great effect by the Trucial Oman Scouts Arab boy signallers (11-14) at Sharjah when communicating with visiting Royal Navy vessels.

The boys, who spoke not a word of English, were for that reason incredibly fast Morse senders and receivers, and did not suffer fools gladly when asked to repeat a message.

Sorry, thread drift!

[NudgingSteel]

Does QNH relate to Nautical Height and QFE relate to Field Elevation?

[Helen49]

or does QNH refer to Newlyn Harbour, the home of Mean Sea Level????
H49

[ChristiaanJ]

Does QNH relate to Nautical Height and QFE relate to Field Elevation?AFAIK, history does not relate whether any Q codes were created with an abbreviation in mind.

Certainly, some like the above lend themselves to easy 'mnemonics', but others are totally random (QUJ is an example).

[Lemurian]

Quote : "...Wikipedia is wrong.

They are both bearings...."
No. The meaning is in fact "heading with no wind".
Those were the days...when an airfield did not have a weather station to give a pilot an altimeter setting but just the "D factor", the difference between the actual airfield elevation andf the pressure altitude as read on the altimeter with a "standard" setting...
The procedure was long and rather complicated as first one had to determinate that the first given sector was correct (one could well have a 180° error) so a heading right or left of the given QDM would after a time cancel that "doubt" (steering left of the QDM would see an increase in the direction).
Then, one had to use a succession of QDMs, using a perpendicular heading to the QDM to compute a distance (with wind), to be correlated to the time it takes to make a vertical-of-station. With the drift that had to be applied to the successive tramsmissions, one could compute the wind velocity and direction.
The rest is about straightforward. One needed to find the outbound leg through a "QDM variation" and fly a wind-correected let-down.
Minima were set at around 6 to 800 ft depending on the airport.
The exercise was very good for materialising one's position relative to the DF station.
The avent of the VOR RMI is , as a matter of fact, the simplification of the VDF let-down, eliminating the ground operator and giving a continuous QDM information to the pilot. The principles are the same.

Quote : "Is my memory correct that in the days when men were men and ATC Controllers knew their stuff, a QGH approach involved the Controller calling for a series of transmissions which, seen on his VDF equipment as QDMs, enabled him to give a series of heading and descent instructions to place one on the glidepath.
"
As seen above, the whole procedure lies on the pilot. He just informed the controller of his position in the approach -with the usual clearances, of course.

This exercise was part of the French airline pilot students training until the late seventies.

[Loose rivets]

I came off a pointy new jet onto a DC3 to get my first command. I had been fortunate to be trained at SEN in the days when we could do almost anything in any weather.

Finding myself in Norwich hollering out bursts of...well, anything really, to give the bloke a bearing, I had trouble changing from one type of bearing to another, until I started to imagine a huge arrow pivoting over the VDF centre and indicating the bearing on a giant compass rose some miles on the other side. Worked well.

Mostly for base-checks, but it's funny how much confidence it gives one when all the T/V screens have gone blank and your'e back to basics.

[old,not bold]

Lemurian,

I think there were two separate N-P approach procedures, both using VDF.

The VDF approach, part of the UK PPL IMC Rating syllabus when I did it and as you say very good for sharpening up one's situational awareness in cloud, was as you say the total responsibility of the pilot; all the Controller had to do was provide QDMs when requested, and authorise the various stages.

The detail you provided brings it all back!

But the QGH procedure, in which the Controller took charge, also existed as an alternative, if the Controller was suitably qualified. I have a feeling that it was used primarily by the RAF, although I did a few at civilian airfields, largely to provide the Controller with some practice. They took an interminable time in a light aircraft, and getting the wind/drift calculation right was a major factor for success; in a fast jet they must have been much more exciting for all concerned, with so much less time to work it all out.