The
airbrake on the 146 is used, at about 100ft, to start the speed reduction so the jet will actually land properly ie not nosewheel first. They are in effect big Cessnas and are difficult to land on the correct spot and if the airbrake is not used to slow down the jet tends to float. Vref, being 1.3Vs, is just too fast for the 146 wing and therefore the airbrake is used to artificially slow the jet down. Not the natural way to fly a jet aeroplane but that's what you get for having a great lifting wing. Nice and stable all the way to 100ft and then it all goes pear-shaped as you firstly pull out the airbrake and secondly pull the power off to idle. Especially as the airbrake imperceptably pitches the nose up, creating a longer float and slow touchdown...thank goodness for the trailing link gear.
The RJ is slightly different, as the autothrottle would put the power up to maintain the speed if the airbrake was put out to early, negating the effect. The airbrake was still pulled out prior ot the flare though.
Engine spoolup is not a consideration in the 146/RJ. The engines are rated to spool up within certification limits from idle power.
The F28 is a slightly different kettle of fish. It settles a little easier and so doesn't need speedbrakes to be pulled out just prior to the flare. We had a company policy that required the speedbrake to be either full out by 700ft or not out until touchdown.
Re use of the speedbrake to control the speed while maintaining constant power, this Fokker idea came with the aircraft but was not generally used as it was not a technique used on any other type and so most pilots were unfamiliar with it. If done "roughly", it resulted in the jet "pulsing" fore and aft and was a bit uncomfortable for the SLF. Better to exercise gentler power control, although the Spey was a bit noisy for those down the back if any throttle bashing was going on.
That said, on both the 146 and the F28 if the speed was too high on final, a good fistful of "fixit stick" worked wonders to get the speed back under control without changing the power too much, especially when asymmetric. Much easier to move the airbrake lever than throttles and rudder!
As for the F100 having only an "out" or "in" speedbrake, I couldn't think of anything worse! Sounds like it'd be very difficult to tickle in a bit of speedbrake to correct a slight profile error.
