Originally Posted by WhiskeySierra
My question: When will the pilot switch the Altimeter from Standard to QNH?
With the first clearance to an Altitute, or when passing the Transition Level. I know it should be the last, but the first seems to be more practicable.
As ever, beware of assumptions.....
The UK AIP (ENR 1.7 para 5.3.1) says 'When an aircraft is descended from a Flight Level to an Altitude preparatory to commencing approach for landing, ATC will pass the appropriate aerodrome QNH. On vacating the Flight Level, the pilot will change to the aerodrome QNH unless further Flight Level vacating reports have been requested by ATC, in which case, the aerodrome QNH will be set following the final Flight Level vacating report'.
And, of course, individual aircraft operator SOPs differ too.