C210T HAS NMAC NEAR ACT.

Narrative

I WAS FLYING LEVEL; SLIGHTLY E OF A SOUTHERLY HDG (ABOUT 170 DEGS); ABOUT 0.7 NM W OF THE ACT CLASS D AIRSPACE (AND ABOVE THE UPPER LIMIT OF THE CLASS D AIRSPACE). I WAS MONITORING WACO APCH; THOUGH NOT IN CONTACT WITH THEM. I HEARD WACO APCH'S ALARM GO OFF IN THE BACKGROUND WHILE WACO APCH WAS XMITTING TO SOMEONE. THEY GAVE AN ACFT A TA WHICH INCLUDED THE WARNING THAT THEY HAD TFC DIRECTLY AHEAD AT THEIR 12 O'CLOCK POS. APPARENTLY HE DID NOT ALTER HIS DIRECTION OF FLT BECAUSE THE NEXT THING THAT HAPPENED SEVERAL SECONDS LATER IS THAT I SAW AN ACFT COMING TOWARDS ME FROM THE SE JUST AS HE PULLED UP AND PASSED VERY CLOSE OVER THE TOP OF ME. I THEN HEARD THE CTLR QUERY HIM. HE REPLIED THAT HE HAD JUST SEEN THE OTHER ACFT PASS JUST BELOW HIM. MY ZAON TFC ALERTER HAD GIVEN ME A WARNING; BUT IT SHOWED THE OTHER ACFT COMING FROM A DIRECTION AT ABOUT 90 DEGS TO THE L OF MY FLT PATH; AND SO I WAS VISUALLY SEARCHING AT THE HORIZON ON MY L. SINCE I DID NOT SEE THE OTHER ACFT; EVEN WITH A WIDE SCAN; I WONDER IF IT WAS CLBING UP TOWARDS ME SUCH THAT I DID NOT SEE IT IN THE GND CLUTTER TO THE SE. IF SO; HE SHOULD HAVE EASILY DETECTED ME SINCE MY AIRPLANE WOULD HAVE BEEN ABOVE THE HORIZON IN HIS VIEW. THE OTHER ACFT WAS HEADING NW AT WHAT I WOULD GUESS TO BE A HDG OF ABOUT 300 DEGS. IF THE OTHER ACFT WAS IN CRUISE; THEN THE OTHER ACFT WAS NOT AN APPROPRIATE ALT FOR HIS DIRECTION OF FLT. HE SHOULD HAVE BEEN AT EVEN +500 FT IF HE WAS FLYING VFR (4500 FT OR 6500 FT); OR ON A 1000 FT ALT IF HE WAS IFR (5000 FT OR 6000 FT). HOWEVER; HE MIGHT HAVE BEEN CLBING OR DSNDING. WHAT I LEARNED FROM THIS IS THE FOLLOWING: 1) I MIGHT HAVE BEEN BETTER OFF IF I HAD BEEN ON FLT FOLLOWING MYSELF INSTEAD OF JUST MONITORING THE WACO APCH FREQ. 2) YOU CAN'T TRUST THE EVEN/ODD CRUISE RULES. SOME PLTS DON'T FOLLOW THEM; AND BESIDES THAT; THE PLT MAY BE CLBING OR DSNDING. 3) THE TFC ALERTER IS NOT VERY ACCURATE ON DIRECTION. DON'T ASSUME THAT IT IS CORRECT TO THE NEAREST 45 DEGS. ASSUME IT IS ONLY GENERALLY CORRECT TO THE NEAREST 180 DEGS.