BE20 PLT TOOK EVASIVE MANEUVER BASED ON A TCASI TA.

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WE WERE BEING VECTORED AT 4000 FT MSL FOR THE ILS RWY 16 AT PALWAUKEE (PWK) WHICH IS N OF O'HARE (ORD). WE WERE IN OR CLOSE TO ORD CLASS B SE OF ORD. THE APCH CTLR ADVISED OF NUMEROUS TARGETS FROM 9 TO 2 O'CLOCK POS. I SAW ON TCASI ABOUT 8 TARGETS IN THE AREA. SOME WERE DROPPING OFF AND REAPPEARING ON THE TCASI. ONLY 1 TARGET SEEMED A PROB. IT WAS AT 1 O'CLOCK POS AND 4 MI; 3500 FT MSL AND CLBING AND TRACKING TOWARD US. APCH WAS BUSY TALKING TO OTHER ACFT. I CALLED APCH TO ASK FOR CLRNC TO 4500 FT MSL. APCH DID NOT RESPOND. AT 2 MI FROM OUR POS THE TARGET WAS 200 FT BELOW US AND CLBING. TCASI SHOWED NO TFC ABOVE ME WITHIN 6 MI. THE TCASI TA WARNING SOUNDED. I CLBED IMMEDIATELY TO 4500 FT MSL. THE TFC PASSED DIRECTLY BELOW US. I DSNDED TO 4000 FT MSL AND TOLD APCH OF THE ALTDEV FOR TFC. APCH THANKED ME AND CLRED ME TO DEVIATE AS NECESSARY FOR TFC. IT WOULD BE WELL TO INCLUDE TRAINING FOR USE OF TCASI AND PLTS' AUTH TO DEVIATE FROM CLRNCS TO AVOID AN EMER IN OUR RECURRENT TRAINING SESSIONS AND IN FAA AND OTHER INSTRUCTIONAL PROGRAMS SO AS TO AVOID PLT INDECISION IN SIMILAR SITS. FOR EXAMPLE; A PLT MAY ATTEMPT TO ADHERE TO HIS LAST CLRNC IN LIEU OF TAKING ACTION TO AVOID COLLISION IF HE HAS NOT PREPARED HIMSELF TO MAKE THE NECESSARY DECISION TO DEVIATE FROM A CLRNC SHOULD IT BECOME NECESSARY. I WILL ALSO IN THE FUTURE TRY TO ANTICIPATE THE NEED TO DEVIATE EARLIER; WILL INFORM ATC OF TCASI CAPABILITY; AND; REQUEST APPROVAL TO DEVIATE AS NECESSARY. SINCE I WAS SINGLE PLT; BECAUSE THERE WERE MANY TARGETS ON THE TCASI AND BECAUSE ONE WAS CONVERGING; I FOCUSED MY PRIMARY ATTN ON AVOIDING THE TARGET. PLACEMENT OF THE TCASI READOUT IN THE PANEL IS IMPORTANT. IT SHOULD BE PLACED WHERE IT CAN BE EASILY INCLUDED IN THE NORMAL SCAN. IT IS ALSO HELPFUL TO PLACE IT WHERE EITHER PLT CAN SEE IT. AN FAA INSPECTOR TOLD ME SEVERAL YRS AGO OF THE VALUE OF THIS EQUIP. WE THEREFORE INSTALLED IT. EVEN THOUGH IT IS NOT REQUIRED FOR PART 91 OPS; WE HAVE BENEFITED FROM IT ON SEVERAL OCCASIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT'S COMPANY INSTALLED THE TCASI EQUIP ON ADVICE FROM OTHERS WHO USED IT. PLT INDICATED THAT HE HAD RECEIVED NO TRAINING ON OP OR THE REGULATORY IMPLICATIONS OF FOLLOWING A TCASI ADVISORY. HE THINKS SUCH TRAINING SHOULD BE MANDATORY TO PREVENT THE HESITATION THAT MIGHT BE PRESENT IN AN UNTRAINED PLT. HE WAS CONCERNED THAT HE HAD VIOLATED HIS ATC CLRNC BY TAKING EVASIVE ACTION IN RESPONSE TO A TA.