CLOSE PROX COMMUTER-LTT GA-SMA.

Narrative

OUR LTT WAS CRUISING AT 7000'; NBND; WHEN THE CAPT CALLED TO MY ATTN AN SMA AT 11 O'CLOCK; APPROX 300' ABOVE OUR ALT (ALTIMETER SET TO TRAVIS APCH LCL VALUE). I GLANCED TO MY LEFT IN TIME TO SEE THE SMA CLOSE ON US. IF WE WERE BOTH AT THE SAME ALT COLLISION WOULD HAVE OCCURRED. THE SMA TOOK 4 SECS MAX TO CROSS OUR FLT PATH. EVASIVE ACTION; EVEN IF THE CAPT HAD DISCONNECTED THE AUTOPLT AND CLBED WITHIN 1 SEC AFTER CONTACT; WOULD PROBABLY NOT HAVE BEEN SUCCESSFUL. I CALLED TRAVIS APCH AS SOON AS HE WAS THROUGH TALKING. THIS TOOK APPROX 30 SECS. I ASKED HIM IF HIS SCOPE SHOWED TFC SEBND ABOUT 7500' MSL. HE STATED 'YES; I HAVE ONE 6 1/2 MI FROM YOU; SEBND.' I RESPONDED 'THAT'S HIM.' THE CTLR THEN CALLED THE SMA AND ASKED HIM HIS ALT. WE HEARD THE SMA PLT RESPOND 7700'. HE WAS SUPPOSED TO BE AT 7500' AND THERE WAS NOT 700' SEPARATING US VERT. I THEN ENDED MY XMISSION TO APCH WITH 'THANKS.' THE CTLR NEVER CALLED THIS TFC TO US; AND HE MADE NO COMMENT AFTER MY 'THANKS.' THE ONLY LOGICAL VARIABLES CREATING THIS INCIDENT WERE OUR 2 ALTIMETER SETTINGS; CTLR VIGILANCE; OUR TFC SCAN; PLT'S ATTN DIVERTED; FATIGUE; ETC. ENOUGH HAS ALREADY BEEN PRINTED RE: HUMAN PERFORMANCE. INEVITABLY; ACCIDENTS WILL OCCUR FROM INCIDENTS WHEN ALL THE VARIABLES ARRIVE AT THE SAME POINT IN TIME AND SPACE. HOWEVER; A COLLISION AVOIDANCE SYS WOULD HAVE PREVENTED THIS. FINALLY; THE SMA ALSO DID NOT SEE US AS HE TOOK NO EVASIVE ACTION.