The airbrake is deployed late on the approach only to facilitate the selection of lift spoilers on touchdown ( as both systems are combined on the same lever).
The fact that the airspeed naturally bleeds from Vref33+5, or whatever your selected increment is to Vref33 ( or if you place faith in BAe's Training guide Vref33-7kts) for touchdown is coincidental.
Use of the airbrake to stabilize the aircraft when conducting a steep approach is an entirely different matter - it is simply necessary in order to maintain a stable speed while having a suitable approach power setting (as per certification requirements). This is the principle reason many other small regional jets are unable to be certified for steep approach op's such as LCY. (i.e. they don't have a tail brake/ airbrake and cannot produce sufficient drag with flap alone).
Carlton Browne, you say "
Using TGT in the cruise to control thrust allows you to gain maximum thrust, as you can run all four engines at max continuous thrust.
Sorry mate, but then why have an MCT mode?? and as underpowered as the 146 is, I have never needed to use MCT in the cruise, even with an engine out.
I personally used to use TGT SYNC in the cruise only because I am incredibly lazy and wanted to be able to make small trust changes by playing with the TGT thumbwheel rather than actually having to move the Trust levers. I would suggest that this is probably what you observed on your DVD safetypee