Glamdring

Each country makes their own rules regarding their airspace. In the UK the document is called the ANO (CAP393)... http://www.caa.co.uk/docs/33/CAP393.pdf Knock yourself out ;)

Nobody "violates" ICAO regs. They are guidelines. In the UK we have our own rules that do differ from ICAO regs in certain areas, but for good reason. We aim to to keep in line with ICAO as much as we can, only just last year we changed from the UK-Only ILS phraseology "When established on the localiser, descend with the glidepath" back to the ICAO "Cleared ILS Approach".

In the UK there is no set rules for altimeter use. Obviously if you are flying inside controlled airspace then ATC will be controlling you by issuing Altitudes and Flight Levels, therefore QNH and SPS will be used. Airline SOPs usually have their own procedures for when to change from QNH to SPS and vice versa. Outside controlled airspace a pilot can set his altimeter to whatever he wants, but he should be aware of certain things... Danger areas, military Training Areas and Controlled Airspace will be shown on charts using Altitudes or Flight Levels and the pilot is still required to avoid them no matter what setting he is using. If in receipt of a radar service he may be asked to stay above/below a certain altitude. Again it is the pilot's responsibility to adhere to this no matter what setting he is using.

Go Here Stick 20'000 in to the Pressure Altitude field and select 29.51 as the QNH. You will see that even though you are FL200, on the QNH you are only at 19617' Hence to fly at 20,000' altitude you need to climb 383' :thumbup:

Imagine yourself turning the altimeter subscale from 29.92 down to 29.51, what happens to the reading on your altimeter? It goes down, hence to fly at 20,000' altitude you would need to go higher. If you want to be at exactly 20,000 MSL fly on the QNH.

I'm the first to admit when I'm wrong :)

As Grzly alludes to the reading we get from the transponder is based on 1013.2. Our radar processors then convert to altitude based on the QNH and where you are on the radar. It's obviously easier this way round as the transition altitude changes depending on where you are, and it also rules out pilot error in setting the subscale. The reason I asked about the slaving is because I was always under the impression that the transponder in most modern airliners had it's own altimeter and encoder (but still fed from the same static source). Could the switch in your image perhaps be to switch between static sources as opposed to altimeters?

Nice to meet you too buddy :thumbup:

Now now, no need to resort to insults. I never pretended to be an expert and I'm certainly not basing my opinions on a game.

I concede that perhaps QFE is more extensively used than I thought. But the fact remains that it is not used at any large airports inside controlled airspace for VFR or IFR. I am basing this on my own experiences as a controller that has worked 5 different sectors during my career, 3 large commercial airports and 2 low level area sector, all with a good mix of GA, commercial and mil traffic. Not once have I been asked for QFE. Fact! The main point I was trying to make in this thread was that I would find it very unlikely that a commercial operator (like AA) would use QFE for anything. The "procedure" or whatever he calls it that Eagle7907 linked to makes no reference to QFE at all. This Thread on pprune appears to confirm that AA did use QFE up until the 1990s but, according to that thread, has followed most other operators in banning the use of QFE. I'm not sure what this "profile" thing that Eagle keeps bleating on about. At the end of the day the approach plate is the law, it tells you how you "must" fly the approach. End of discussion. The other posts I have made in this thread were to correct obvious mistakes and misinformation... Also since when did aircraft have 2 transponders? And why would any of them need to be slaved to the cockpit altimeters? Genuine question?

Your definition of "Busy Commercial Airfield" obviously differs from mine. Try getting a VFR transit or do circuits using QFE at Glasgow, Aberdeen, Edinburgh, Manchester, Birmingham, Cardiff, Southampton, Luton, Gatwick or Stansted and see how far you get. The fact remains that, in the UK, with the exception of the RAF and VFR GA doing circuits at largely GA airfields, QFE is not used. Like I said, I've been a controller for almost 10 years and never used it once.

The vast majority of GA airfields don't have ATC so they can do what they like. Fly VFR in to any commercial airport or even try and transit their zone and you will be given a clearance at an altitude, not a height. Hence QNH.

I don't fly commercially. I do however control commercially and I have not once used or given out QFE. I think you are confused by the terminology, by definition altitude is height above MSL hence QNH. QFE is never Altitude. QNH = Altitude QFE = Height SPS = Flight Level The procedure you linked does indeed reference AAL (Above Aerodrome Level). However they are still climbing to a Missed Approach "Altitude" hence will have QNH set. As pointed out above they will use either a radar-alt to provide the AAL references or add field elevation onto the referenced heights to convert to Altitude. No requirement for QFE there at all. As for approach procedures and missed approach procedures they are all on the approach plate (where everything is flown with reference to QNH). e.g. Edinburgh 06 ILS Humberside 02 NDB

That would depend on where you're doing circuits. If at any decent sized airport inside CAS then you will be given a VFR circuit clearance not above an altitude. Altitude = QNH. And to those who would suggest that a controller would happily have QFE and QNH traffic close to each other and would personally calculate the differences, sod that, way to much like hard work. A controller will tell you to fly at an altitude, hence QNH. You may ask for QFE and use it for your own purposes, but if you are instructed to fly at an altitude (which you will be in the UK) then it's up to you as the pilot to adhere to your clearance. QFE may be used at uncontrolled GA aerodromes but it certainly has no place in the commercial world. The only real value of QFE is to make a circuit look pretty on the altimeter. Probably why the RAF still use it, they like pretty things, like medals and stuff ;)

I doubt that AA would use QFE when everybody else around them is using QNH.

SR71 F-302 (From Stargate) Gunstar (From The Last Starfighter) X-Wing

Done. Although I did find it rather over-complicated.

:thumbup: Well, if you guys did what you were told....