UNAUTH TKOF STARTED BY 1 OF 2 ACFT WITH SIMILAR SOUNDING A/N. MULTIPLE RWY OP INTERSECTING XING RWYS.

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I WAS THE CAPT OF FLT AB MOVER EDHA FROM BOS TO MVY ON OCT/FRI/96. WHILE TAXIING TO RWY 9 AT BOS; THE TWR CTLR ASKED US IF WE COULD ACCEPT AN INTXN 'W' DEP ON RWY 9. OUR ARPT ANALYSIS DID NOT HAVE DATA FOR AN INTXN 'W' DEP SO I DECLINED AND INFORMED THE TWR CTLR WE WOULD NEED THE FULL LENGTH OF RWY 9. WE WERE HOLDING SHORT OF RWY 9 AT INTXN 'W' AND WERE CLRED BY TWR TO TAXI THE FULL LENGTH OF RWY 9 INTO POS AND HOLD. I WAS AT THE CTLS. AS I WAS TAXIING AND TURNING THE ACFT 180 DEGS ONTO CTRLINE THE TWR ISSUED THE TKOF CLRNC; 'AB MOVER EDHA CLRED FOR TKOF.' MY FO READ BACK THE TKOF CLRNC; 'AB MOVER EDHA CLRED FOR TKOF RWY 9.' THERE WAS NO REPLY FROM TWR TELLING US WE READ THE CLRNC INCORRECTLY OR THAT WE WERE NOT CLRED FOR TKOF. THE FO STATED TO ME OVER THE INTERPHONE 'CLRED FOR TKOF' AND I AGREED. I TRANSFERRED THE CTLS TO THE FO SINCE IT WAS HIS LEG TO FLY. APPROX 5- 10 SECONDS HAD ELAPSED BTWN THE TIME THE FO HAD FINISHED THE TKOF CLRNC READBACK AND HE BEGAN TO ADVANCE THE PWR LEVERS TO BEGIN THE TKOF ROLL. STILL NO XMISSION FROM TWR TELLING US WE WERE NOT CLRED FOR TKOF. AS OUR AIRSPD REACHED APPROX 40-50 KTS THE TWR CTLR SAID 'AB MOVER EDHA STOP.' I CALLED 'ABORT; ABORT' OVER THE INTERPHONE AND THE FO IMMEDIATELY INITIATED THE ABORT AND STOPPED THE ACFT ON CTRLINE WITHOUT INCIDENT. WE HAD CROSSED RWY 4R WHICH INTERSECTS RWY 9. WE WERE TOLD TO EXIT RWY 9 AT INTXN 'E' AND WE DID. WE WERE CLR OF RWY 9 ON TXWY 'E.' A VOICE ON THE FREQ SAID 'WHAT HAPPENED?' AND A REPLY FROM THE TWR OF 'I DON'T KNOW; WE'RE LOOKING INTO IT.' THE TWR CTLR TOLD A 'XXAB MOVER FOHA TURN L FOR RESEQUENCE FOR DEP.' THIS IS THE FIRST TIME WE WERE AWARE THERE WAS ANOTHER ACFT WITH A SIMILAR CALL SIGN ON THE FREQ. GND OR TWR CTLRS NEVER ADVISED US THERE WERE SIMILAR CALL SIGNS ON THE SAME FREQ. OUR CALL SIGN WAS 'AB MOVER EDHA' AND THEIRS WAS 'XXAB MOVER FOHA.' WHEN THE TKOF CLRNC WAS ISSUED THE TWR CTLR ONLY USED THE WORD 'MOVER.' WE DID NOT HEAR 'AB' OR 'XX' FIRST. SINCE OUR CALL SIGNS WERE SO SIMILAR WE APPARENTLY BOTH BEGAN OUR DEP ROLLS. WE NEVER HEARD ANOTHER ACFT READ BACK THE TKOF CLRNC AND WERE NOT ADVISED WE HAD MISREAD A TKOF CLRNC FOR ANOTHER ACFT WITH A SIMILAR CALL SIGN. I WAS TOLD I WOULD HAVE TO CALL BOS TWR WHEN I REACHED MY DEST; WHICH I DID. I WAS TOLD THEY WERE INVESTIGATING A PLTDEV SINCE 2 ACFT WERE ROLLING SIMULTANEOUSLY ON INTERSECTING RWYS. WE NEVER SAW OR HEARD ANOTHER ACFT ON OUR TKOF ROLL. THERE WAS NO NEAR MISS THAT WE COULD SEE. THE BOS CTLR I CALLED AFTER ARR AT MVY NEVER SAID I WAS THE ACFT THAT BEGAN TO MOVE WITHOUT CLRNC. ACFT DEPARTING FROM THE FULL LENGTH OF RWY 4R AT BOS START THEIR TKOF ROLL FROM BEYOND A DISPLACED THRESHOLD APPROX 1500-2000 FT FROM THE INTXN OF RWY 4R AND RWY 9. THE RWYS ARE ALIGNED AT APPROX 45 DEGS TO EACH OTHER SO IT IS DIFFICULT FOR AN ACFT HOLDING IN POS ON RWY 9 TO SEE ANOTHER ACFT HOLD IN POS ON RWY 4R BEYOND THE DISPLACED THRESHOLD. WHEN WE WERE INITIALLY CLRED INTO POS AND HOLD ON RWY 9 THE TWR CTLR TOLD US THERE WOULD BE ONE ARR PRIOR TO OUR DEP ON THE INTERSECTING RWY 4R WHICH THERE WAS; A B737. THE TWR CTLR DID NOT TELL US THERE WOULD BE A DEP FROM THE INTERSECTING RWY 4R PRIOR TO OUR DEP. WE WERE NOT ADVISED ANOTHER ACFT WITH A SIMILAR CALL SIGN WAS HOLDING ON THE INTERSECTING RWY 4R. THERE HAS BEEN CONFUSION IN THE PAST WITH THE SIMILARITY IN THE CALL SIGNS BTWN OUR COMPANY AB MOVER AND XXAB MOVER TO THE EXTENT THAT OUR COMPANY ISSUED A MEMO TO ALL PLTS TO ALWAYS USE OUR FULL CALL SIGN 'AB MOVER' AND NOT TO REPLY WITH JUST 'MOVER.' IF THE TWR CTLR HAD USED 'AB' OR 'XX' PRECEDING THE WORDS 'MOVER EDHA' IN HIS TKOF CLRNC; IT WAS NOT HEARD BY MYSELF OR THE FO. IF WE HAD BEEN ADVISED AN ACFT WITH A SIMILAR CALL SIGN AND FLT NUMBER WAS ON THE FREQ I FEEL THIS SIT COULD HAVE BEEN AVOIDED. FATIGUE WAS NOT A FACTOR WITH MYSELF OR MY FO. WE HAD ONLY FLOWN 2 PREVIOUS LEGS FROM HYA TO MVY AND MVY TO BOSTON. WE WERE BOTH WELL RESTED. OUR RPT FOR DUTY TIME WAS XA30 PM. I KNOW THAT AT A BUSY ARPT LIKE BOS; CTLRS DON'T HAVE TIME TO ALERT PLTS EVERY TIME THERE IS A SIMILAR CALL SIGN ALONE ON THE SAME FREQ; BUT WHEN 2 ACFT WITH SIMILAR CALL SIGNS AND SIMILAR FLT NUMBERS AB MOVER EDHA AND XXAB MOVER FOHA ARE ON INTERSECTING RWY; PLTS MUST BE ADVISED -- ESPECIALLY IF CTLRS DROP THE 'AB' OR 'XX' PREFIX AND JUST USE 'MOVER' AND THE FLT NUMBER. THIS WAS AN EVENT THAT COULD HAVE BEEN AVOIDED. WE WERE A FEW MINS BEHIND SCHEDULE BUT WE WERE NOT RUSHING. WE HAD ENOUGH TIME ON THE GND AT MARTHA'S VINEYARD THAT WE WOULD BE BACK ON SCHEDULE FOR OUR RETURN TRIP TO BOSTON. WE ACCEPT THE DELAYS WE EXPERIENCE AT BUSY ARPTS LIKE BOSTON AND DON'T RUSH TO GET BACK ON SCHEDULE. THIS WAS NOT A FACTOR IN THIS OCCURRENCE. IF WE HAD HEARD THE XX MOVER SAY SOMETHING LIKE 'WAS THAT TKOF CLRNC TO XX MOVER FOHA' OR IF THE CTLR HAD TOLD US WE WERE NOT CLRED FOR TKOF OR ANYTHING TO GIVE US SOME INDICATION THERE WAS ANY MISUNDERSTANDING WITH THE TKOF CLRNC WE WOULD HAVE CONTINUED HOLDING IN POS AND ASKED FOR CLARIFICATION OF THE TKOF CLRNC.