FL flying

[XL319]

At what altitude do you change to FL instead of flying on a region pressure?

Do you change automatically at 5000ft or is it your decision whether you fly at the regional pressure (i.e. Barnsley QNH)

[Diaz]

Wikipedia is quite usefull soemtimes;

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

[BigAl's]

Depends where the transition level is on the day (the transition layer changes with pressure alt), if you were flying IFR in the UK you would change to 1013.2mb/hpa at 3000' QNH.
Now, if you are VFR, you can do that (and fly quad levels etc), but I have flown on the QNH around and about at 4000' quite happily.

That's my understanding, but I'm probably wrong (I don't have the book to hand) so someone, please put me right! :bored:

[Chilli Monster]

Flight Levels are mandatory for IFR flights above Transition Altitude.

Transition Alt is 3000ft in the UK FIR's, but higher within most CTA's / TMA's (London and Scottish - 6000ft, East Midlands 4000ft etc - all available in the UK AIP ENR section under Altimeter Setting)

Go elsewhere it can be higher - USA is 18000ft.

Flight Levels are only recommended for VFR flights above Transition Altitude.

So - the answer to your question - if you are going to change, or need to change, you change at Transition Altitude.

As a footnote - Regional Pressure setting. DO NOT use this if you are in the vicinity of Controlled Airspace where the base level is defined as an altitude. YOU WILL INFRINGE.

You should be on the QNH of the airport concerned or a nearby one to ensure you remain outside CAS. Personally I only use RPS if there is nothing else available - which is very rare.

[XL319]

The reason i ask is that London Info asked if i was flying FL or alt when i was at 6,700ft on the Barnsley. Should I have been on FL instead? IS it mandatory to change at such a low alt

[Chilli Monster]

Read what I said above - that's the definitive rule.

However - it depends what the base of CAS was above you as I said before (indeed - the base of CAS could have been below you and you might have been in it ;) )

[XL319]

ok thanks i get the gest of it now...it was class G that I was in at the time, but FL may have been better.

cheers for the comments