ppl confusered..

[the ace of spades]

ppl confuser question.
you are in straight and level flight (outside of controlled airspace) on a heading of 095. due to wind drift your magnetic track is 087. the QNH is 994 mbs. if you wish to comply with the quadrantal rule, you should fly at:
a. an indicated 5000 ft with altimeter setting of 1013 mbs.
b. an indicated 5500 ft with altimeter setting of 1013 mbs.
c. an indicated 3000 ft with an altimeter setting of 1013 mbs.
d. an indicated 3500 ft with an altimeter setting of 1013mbs.

i answered c. confuser says a. explain please.

:ok:

[BackPacker]

3000 feet is below the transition layer (actually it is the transition altitude in the UK) so you should be flying on the QNH then, not on 1013.

5000 feet is above the transition layer, except on days with very, very low air pressure (and you probably shouldn't be flying then, due to the weather), so you should be flying on 1013.

[the ace of spades]

so if i was on magnetic track of 139 for example i would be flying at 3500 on 1013 mbs?!

[BackPacker]

The thing is, it's actually two questions in one. It requires you to understand the quadrantal rule and it requires you to understand the difference between flight levels and altitudes, and the function and lower/upper limit of the transition layer.

The highest "altitude" you can fly is 3000 feet on the local QNH, because 3000 feet is defined as the transition altitude (in the UK, outside controlled airspace). You then punch through the transition layer where you reset your altimeter to 1013, and the first FL you hit (multiples of 500 feet) is the lowest FL you can fly.

3000 feet on the 994 QNH is equal to 3000 + (1013-994)*30 feet = 3570 feet on 1013. That means that FL35, in this particular scenario, would be (70 feet) *below* 3000 feet altitude. Because of this, FL35 is not available today. Due to the low QNH. The first usable FL is 40. And FL 40, because of the same calculation, is only 430 feet higher than 3000 feet on the QNH.

So there's no way, with a QNH of 994, that you can do all things right and have the altimeter display 3500. You either fly below the transition layer, in which case you fly at 3000 feet or below on the 994 QHN, or you fly above it, at FL40 or above (with 1013 set).

So on this particular day, if you want to fly to the quadrantal rule, and fly a magnetic track of 139, you've got to fly at either 1500 on the 994 QHN, or at FL55 (5500 on 1013).

(All this of course assumes you want to fly to the quadrantal rule, so this implies that you are flying with the proper QNH set below the transition layer, or with 1013 set above the transition layer. But that's not a requirement for VFR flight so outside this question you've got a lot more flexibility.)

[FlyingKiwi_73]

The UK transition layer is between 3000 and 5000ft????? is everybody in the UK shorter than the southern hemisphere? in NZ the layer is between 13000 and 15000 feet (sorry FL15), do you guys have different rules for levels going north and south like we do?

Odd odd odd..... is it cos we is mountainous?

[BackPacker]

Kiwi, the transition altitude is 3000' (in the UK, outside controlled airspace). That's the only thing that's defined. The transition level is the first usable FL above the transition altitude. This implies that, depending on the exact QNH, the transition layer can be anywhere between 0' and 499' thick.

But yes, the transition altitude varies by country. And in the UK, there are bits of controlled airspace that have a TA of 6000' even. In the Netherlands, it's 3000 for IFR, 3500 for VFR. In the USA it's 18.000'. Different countries have different considerations as to where they put the TA. Geography (mountains or not) does play a part in that. In the Netherlands for instance, there's not a lot of terrain that rises to 3000'. In fact, you'd be hard pressed to find terrain here significantly higher than 1000', so a TA of 3000' works fine for us.

Europe is trying to harmonize the TA, but as with all things European, this takes time.

And while most of the rest of the world has standardized on a semi-circular rule (VFR: odd thousands + 500' anywhere between 0 and 180, even thousands + 500' anywhere between 180 and 360) or a variant thereof, the UK still uses a quandrantal rule (odd thousands 0-90 degrees, odd thousands + 500' 90-180, even thousands 180-270, even thousands + 500' 270-360).

Flight level - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Flight_level)

[FlyingKiwi_73]

I have just done a quick google and found our highest Mountain is 12,316 ft AMSL, our transition layer starts at 13,000 ft, can't be a co-incidence?

Its odd how our layer is a mandatory 2000ft thick but the UK is dependant apon area QNH? that must be annoying having to work out which level you need to be as fronts come through etc...

Mind you our airspace is a lot less constricted in NZ wtih most of it Being G with a smatering of C.... and bugger all A class so i guess we are bit 'free and easy'

[BackPacker]

I think the idea in NZ is that the layer always runs from 13.000' to FL150. In ISO conditions (QNH 1013) this means that the layer is 2000 feet thick. With a low QNH the layer will be thinner, and with a high QNH the layer will be thicker.

But you'd have a ridiculously low QNH to let FL150 be *lower* than 13.000', so that makes calculating the lowest available FL a doddle. Since it's always FL150.

On the other hand, you're essentially throwing away a whole 2000' (plus or minus some feet) of airspace. Simply because there's no formal way of altitude reporting when you're in the transition layer (you're "in transition" after all). So you can't fly there and be assured of vertical separation and such. If you have that 2000' to spare, fine. In congested airspace, airspace is actually a valuable resource.