A STEMME SAILPLANE TOOK EVASIVE ACTION TO AVOID A COLLISION WITH ACR ACFT.

Narrative

WHILE FLYING A WESTERLY COURSE APPROX 15 NM FROM SJC ON ITS 45 DEG RADIAL AT 6000 FT MSL; I OBSERVED AN AIRLINER APCHING ME ON WHAT APPEARED TO BE A COLLISION COURSE FROM MY 10 O'CLOCK POS. WHILE THE OTHER ACFT APPEARED TO BE DSNDING; SINCE IT WAS ABOVE MY ALT; I TURNED R AND DOVE. I BELIEVE THE OTHER PLT ALSO TOOK EVASIVE ACTION; BUT CANNOT BE SURE. THE LARGE SIZE OF THE AIRLINER MAY HAVE MADE MY DISTANCE AND ALT SEPARATION ESTIMATES (1000 AND 500 FT RESPECTIVELY) SMALLER THAN THEY WERE; BUT I SUSPECT THE SEPARATION WAS LESS THAN DESIRED. MY ACFT IS A MOTOR GLIDER; I WAS IN GLIDER MODE (ENG OFF) AT THAT POINT IN TIME; AND DSNDING TO SET UP FOR A LNDG AT HWD. MAINTAINING A NORMAL VFR CRUISING ALT WAS THEREFORE NOT POSSIBLE OR APPROPRIATE. MY XPONDER WAS SET TO 1200 AND WAS BEING INTERROGATED FREQUENTLY. WHILE 'SEE AND AVOID' IS THE RULE IN VMC; THE HIGH SPD OF JETS MAKES TCAS AND OTHER COLLISION AVOIDANCE AIDS HIGHLY USEFUL. I AM SURPRISED THAT THE AIRLINER'S TCAS DID NOT PICK ME UP SOONER.