VS and Speedbrake don't work very well together for the reasons stated above, the only reason to use this combination is if you were unusually assigned a particular RoD and were trying to get the speed back. If you PULL 250kt and PULL 2500 Vs, VS being a basic mode mode will have greater priority over SPEED mode and you will accelerate away from your selected speed target. This situation will continue until an overspeed occurs, when the OS protection will temporarily override the VS command and pitch the a/c up to maintain vmax. It is possible to use the speedbrake to prevent this, but it would look and feel untidy.
If ATC are being unreasonable with your 250kts/2500fpm scenario, you can consider:
taking the autopilot out which on most A320's allows maximum Speedbrake to pop out, instead of the just over 50% with Ap engaged, this works a treat. It does not work on A321's and other specific Airbuses, so check your MSN.
If you are really stuck and are quite close in to destination, state 'non standard' and get the gear down. This technique is completely appropriate and combined with the full speedbrake gives a very sporting Rod. But it requires a bit of the mental arithmetic that as discussed in a previous thread.
I make no claim to being a Airbus expert, so this just line stuff which I might use in a specific situation, that I know will work OK.
Good questions OP, keep 'em coming.
ps. once upon a time there used to be a breed of pilot that regarded it as a matter of honour that they didn't use the speedbrake ever and actually laughed at you if you did, thankfully this has largely died out.
Last edited by macdo; 8th Jun 2012 at 19:39.