QNH CHANGES WHEN?

[a319320]

I had to do a ferry the other day and we were
below the transition altitude all the way.
I'm not sure when one changes from departure
QNH to area and then destination QNH,could
someone enlighten me please?
Thanks

[wysiwyg]

If staying below transition:

within/below TMA - terminal area QNH
clear of TMA/en route - regional pressure setting
back within/below TMA - terminal area QNH again

regards
wizzy

[a319320]

thanks wysiwyg!

[A Very Civil Pilot]

If you're aerodrome wasn't under a TMA, aerodrome QNH is valid for a radius of 25nm. (obviously more relevant for the GA end of the market).