On the ground the BAe146 TMS default temperature was the sensed ambient from the TAT probe. However, the tower temperature should always be set as the TAT probe could suffer errors due to reflections from hot concrete, etc. If you didn’t have a tower temp available in foreign parts / hot climes, then use a wet face cloth to cool the probe down!
A flex takeoff used the assumed temperature method; a false ambient temperature is set in the TMS. The flex N1 must be checked against the tables of expected and allowed thrust reductions.
The TGT mode with N1 synchronisation to the hottest engine was used during the climb to maximise engine life; the cruise was normally flown in N1 sync. The engine does not use EPR. The Avro RJ has a different system embedded in the flight guidance computer.
The airbrake was very effective; a selection on late finals gave a consistent speed reduction for the flare and landing. The airbrake and full flap were mandatory for steep approaches as they provided a larger drag margin to manoeuvre the aircraft about the glideslope.