I use them both, a lot.
In the Netherlands the TA is 3000’ (IFR) or 3500’ (VFR). Anything below that (including airspace boundaries) is defined as an altitude, anything above as a FL. The location where we practice aerobatics, in the Rotterdam TMA, is defined from 1500’ to FL55. We usually train fairly high, so we get a block between 3000’ and FL55. Which is something that you need to think about just a bit: If the QNH is above 1013, that block is more than 2500’ high, if the QNH is lower than 1013, you have less than 2500’ to play with. You have to account for this in your routine.
The practical trick that we use is to keep the altimeter on the QNH, and read the FLs from the transponder.
EHAA AIP, ENR 1.7 para 1.1:
1.1 Transition altitude/transition level
The transition altitude is 3000 ft for IFR flights and 3500 ft for VFR flights in the entire Amsterdam FIR.
The transition level for the entire Amsterdam FIR is positioned at or above 4000 ft AMSL and is determined hourly.
One fun bit is if say the TL is 10000ft and you are cleared to climb to FL160, at which point do you set 1013? And similarly on the way down.
Officially when passing the TA; operationally single-pilot, when starting the climb.
You set 1013 before starting the climb? you will only get caught when ATC ask you to level up while on the climb or report altitude bellow TA 
Same for setting QNH you can set it when cleared to descent to altitude (as long as you don’t expect to level up above TL)
Exception, sometimes you get FL100 in departure clearance and say max 3kft in takeoff clearance, I imagine you always stay on QNH first, same every time your departure may involve MSL or AGL
The question is irrelevant if you have two altimeters with 2nd one always on QNH (even when en-route you pick ATIS of the place you pass overhead and update)
Peter wrote:
One fun bit is if say the TL is 10000ft and you are cleared to climb to FL160, at which point do you set 1013? And similarly on the way down.
That’s well defined. If you’re cleared to a level above the TA, you can either set 1013 when starting the climb or when passing the TA – your choice. Similarly, if you’re cleared to a level below the TL, you can either set the QNH when starting the descent or when passing the TL.
Ibra wrote:
You set 1013 before starting the climb? you will only get caught…
Nothing to get caught for. That’s an approved procedure. https://www.skybrary.aero/index.php/Transition_Altitude/Level#Europe
Airborne_Again wrote:
Nothing to get caught for. That’s an approved procedure
So ATC won’t level you at an altitude bellow TA if they previously cleared to climb to some FL?
If ATC clears you to a flight level lets say (Fl150)
and then asks you after you have started the climb to level off at lets say 5000ft, there would usually have to be a very good reason to rescind a clearance and they would give you the QNH in the same message. Eg G ABCD maintain 5000ft QNH 1021 unknown traffic.
Peter wrote:
I wonder who uses both in Europe?
Everyone who ever gets into FL territory hopefully.
Peter wrote:
I know the UK uses both, and most pilots don’t know the difference.
Then there is something amiss with the theoretical knowledge. This is basic altimeter stuff which people really need to know.
Peter wrote:
One fun bit is if say the TL is 10000ft and you are cleared to climb to FL160, at which point do you set 1013? And similarly on the way down.
On climb you set 1013 when passing TA. In descent you set QNH wenn passing TL. TL is adapted for pressure, so it changes. TA is fixed
If you are under ATC control and are issued a climb/descent clearance through either, it is common practice to set the altimeter according to the clearance, that is QNE for a climb through TA and QNH for a descent through TL as soon as you leave the last assigned FL/altitude.
The thing where people need to watch out is what the TA/TL is for a given set of airspace. As several posters have indicated already, this can lead to difficulties. If you are under ATC control you’ll be cleared to a FL or Altitude depending, so there it is not an issue.
lionel wrote:
Officially when passing the TA; operationally single-pilot, when starting the climb.
I agree with this, it’s much safer… Technically wrong probably, but a lot safer…
