THE CAPT OF AN A319 WITH 1 OF 2 BSCU'S INOP QUESTIONS THE EFFECTS ANOTHER BSCU FAILING. WITHOUT AN ANSWER HE REQUESTS THE ACFT BE FIXED.

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WE HAD A BSCU #1 DEFERRED INOP; THERE IS NO DISPATCH RESTR WITH THIS SITUATION. THE ONLY PROB WITH THE DEFERRAL IS THAT IF THE OTHER BSCU GOES INOP THE ACFT IS NOW IN A SITUATION OF BEING IN ACCUMULATOR BRAKES WITH NO ANTI-SKID AND NOSEWHEEL STEERING. THE REAL SITUATION IS THAT WHEN I ASK WHAT ELSE IS LOST WITH THE SECOND FAILURE THEY DO NOT KNOW. THAT IS WHY I WILL NOT FLY WITH THE BSCU INOP. WE NOTIFIED MAINT AND THE FIRST MECH SHOWED UP AFTER 30 MINS; HIS WORDS WERE 'I CAN'T HELP YA HERE; WOULDN'T KNOW WHERE TO START; I AM A 777/400 GUY.' IT THEN WAS 30 MORE MINS AND 2 R&E GUYS CAME UP TO THE COCKPIT AND TOLD US THEY WOULD BE WORKING ON IT. ABOUT 15 MINS LATER THEY WERE OUT WORKING A SPD SENSOR ON THE #1 WHEEL. IT TOOK THEM 30 MINS TO GET THE SPD SENSOR OUT OF THE WHEEL. I WENT DOWN TO DISCUSS THE TIME SITUATION WITH THEM; THEY BOTH HAD NEVER DONE THIS PROC. BY THIS TIME I HAD ALREADY GONE UP TO THE BOARDING AREA AND MADE AN ANNOUNCEMENT TO THE PAX TO LET THEM IN ON THE SITUATION. ABOUT 20 MINS LATER WE WERE GIVEN A NEW ACFT AT GATE X THAT HAD JUST ARRIVED. THERE WAS NO REASON FOR THIS DELAY TO HAVE BEEN 2 HRS 30 MINS THE MAINT IN ZZZ GAVE US 2 HRS OF DELAY.