Narrative:

We were on the zzzzz arrival into ZZZ; descending to 12000 ft to meet the crossing restr; when the controller told us to descend to 11000 ft for traffic. We saw a target at 500 ft above on the TCAS (just appeared) and as we increased our rate of descent we got a traffic alert and the target turned to orange on the TCAS. We saw a glider and reported it to ATC (we previously heard him alert another aircraft of an unidented target in the area; possibly a glider) as the glider passed slightly to our 1 O'clock position; another glider appeared directly at 12 O'clock position; the PF banked steeply to the right and descended further to avoid the glider. Looking to my left 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 controller we were diverting for another glider and we went below our assigned altitude by over 400 ft while recovering. Both gliders were flying just above the ridge; a great place to soar; but precisely on the arrival path and altitude. Only 1 TA was visible on the TCAS. This was a great call from the controller; as xmissions were the usual busy ZZZ arrival on a friday evening. After a moment of silence; I advised the controller again that there were 2 gliders on the arrival above the ridge. I will attempt today to call the TRACON to discuss the altitude deviation and thank the controller for his vigilance.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.