C550 FLT CREW TOOK EVASIVE ACTION TO AVOID GLIDER ACTIVITY.

Narrative

WE WERE ON THE ZZZZZ ARR INTO ZZZ; DSNDING TO 12000 FT TO MEET THE XING RESTR; WHEN THE CTLR TOLD US TO DSND TO 11000 FT FOR TFC. WE SAW A TARGET AT 500 FT ABOVE ON THE TCAS (JUST APPEARED) AND AS WE INCREASED OUR RATE OF DSCNT WE GOT A TFC ALERT AND THE TARGET TURNED TO ORANGE ON THE TCAS. WE SAW A GLIDER AND RPTED IT TO ATC (WE PREVIOUSLY HEARD HIM ALERT ANOTHER ACFT OF AN UNIDENTED TARGET IN THE AREA; POSSIBLY A GLIDER) AS THE GLIDER PASSED SLIGHTLY TO OUR 1 O'CLOCK POS; ANOTHER GLIDER APPEARED DIRECTLY AT 12 O'CLOCK POS; THE PF BANKED STEEPLY TO THE R AND DSNDED FURTHER TO AVOID THE GLIDER. LOOKING TO MY L I SAW A FLASH OF PARTIAL GLIDER PASS ABOVE US (WE WERE CLOSE ENOUGH THAT THE COMPLETE WING SPAN WAS NOT VISIBLE). I ADVISED THE CTLR WE WERE DIVERTING FOR ANOTHER GLIDER AND WE WENT BELOW OUR ASSIGNED ALT BY OVER 400 FT WHILE RECOVERING. BOTH GLIDERS WERE FLYING JUST ABOVE THE RIDGE; A GREAT PLACE TO SOAR; BUT PRECISELY ON THE ARR PATH AND ALT. ONLY 1 TA WAS VISIBLE ON THE TCAS. THIS WAS A GREAT CALL FROM THE CTLR; AS XMISSIONS WERE THE USUAL BUSY ZZZ ARR ON A FRIDAY EVENING. AFTER A MOMENT OF SILENCE; I ADVISED THE CTLR AGAIN THAT THERE WERE 2 GLIDERS ON THE ARR ABOVE THE RIDGE. I WILL ATTEMPT TODAY TO CALL THE TRACON TO DISCUSS THE ALT DEV AND THANK THE CTLR FOR HIS VIGILANCE.