GC1 ARRIVING ACFT CONFLICTS WITH DEPARTING TFC IN SGR AIRSPACE.

Narrative

PLT WAS FLYING A PRACTICE ILS APCH TO RWY 35 IN VMC 'UNDER THE HOOD.' ACTIVE RWY WAS RWY 17. I WAS ACTING AS SAFETY PLT IN 2-SEAT SINGLE ENG ACFT. THE APCH WAS FLOWN OUT OF A HOLDING PATTERN AT THE FAF. THE TWR CTLR AT THE ARPT HAD INSTRUCTED THE PLT TO RPT LEAVING HOLD. PLT ANNOUNCED LEAVING HOLD AND PROCEEDED INBOUND ON THE ILS. NO RESPONSE FROM THE CTLR; BUT AT THE TIME THERE WAS ONGOING CTLR COMS WITH AN ACFT SHOOTING TOUCH-AND-GOES AND ANOTHER ACFT PREPARING TO DEPART. PLT RPTED INBOUND AND THE FAF. AGAIN; NO RESPONSE FROM THE CTLR; BUT CONTINUED HVY RADIO TFC WITH OTHER ACFT. AS PLT CONTINUED INBOUND ON THE ILS APCH; THE CTLR CLRED AN ACFT TO DEPART ON RWY 17. GIVEN OUR POS ON THE APCH THIS DID NOT SEEM RIGHT AND I BROUGHT THIS TO THE ATTN OF THE PLT. I THEN OBSERVED THAT THE ACFT SHOOTING TOUCH-AND-GOES WAS CLBING OUT TOWARD US AND INSTRUCTED THE PLT TO BREAK OFF HIS APCH TO THE E TO AVOID THE CLBING ACFT. JUST AFTERWARDS; THE CTLR SAW OUR ACFT; INSTRUCTED THE CLBING ACFT TO TURN W AND INSTRUCTED THE ACFT THAT HAD BEEN CLRED FOR DEP TO ABORT HIS TKOF RUN. THE CTLR REPRIMANDED MY PLT FOR PROCEEDING INBOUND WITHOUT RADIO CONTACT. WHEN MY PLT ATTEMPTED TO REPLY IT WAS CLR THAT HIS RADIO WAS RECEIVING BUT NOT XMITTING. AFTER SEVERAL XMISSION ATTEMPTS; IT WAS DISCOVERED THAT THERE WAS AN INTERMITTENT PROB WITH THE PUSH-TO-TALK SWITCH ON HIS RADIO. THIS CONFLICT RESULTED FROM A COMBINATION OF AN EQUIP PROB (PUSH-TO-TALK SWITCH FAILURE) AND HUMAN ERROR (FAILURE TO ENSURE PROPER COMS). THE PLT SHOULD HAVE ENSURED THAT THE CTLR ACKNOWLEDGED HIS POS RPTS (ALTHOUGH AT THE TIME THIS LAPSE DID NOT SEEM ALARMING DUE TO THE BUSY RADIO TFC). ENOUGH TIME HAD ELAPSED SINCE THE LAST CTLR COMS THAT THE CTLR (KNOWING THE PLTS INTENTIONS) SHOULD PROBABLY HAVE CALLED THE PLT TO CHK ON HIS SIT. THE SAFETY PLT SYS WORKED WELL TO AVOID A MORE SERIOUS PROB; ALTHOUGH IN RETROSPECT THE SAFETY PLT SHOULD HAVE PLAYED A MORE ACTIVE ROLE IN MONITORING THE COM SIT.