A FOKKER 70 CPR FLT DSNDING TO 3000 FT ON A VECTOR FOR ILS RWY 24L AT CLE HAS AN NMAC WITH A GA ACFT MAKING A CLBING L TURN OUT OF BKL; OH.

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THIS IS A RPT OF ELECTRONIC SENSORY SATURATION DURING A CRITICAL PHASE OF FLT AND HOW IT IMPEDED COCKPIT COMS. WX: CLR SKIES AND UNLIMITED VISIBILITY. DSNDING THROUGH 7000 FT; ON RADAR VECTORS FOR THE ILS RWY 24L AT CLE; OUR FLT WARNING COMPUTER GENERATED THE LEVEL III ALERT 'LNDG GEAR NOT DOWN.' AGAIN; WE WERE WELL ABOVE THE ALERT ENVELOPE AND ABOVE LNDG GEAR OPERATING SPD. RIGHT AWAY I NOTICED THE L SEAT RADAR ALTIMETER WAS READING ZERO FT. THIS ERRONEOUS INPUT WAS GENERATING THE ALERT. ON THE FOKKER 70 YOU CANNOT SILENCE THE LNDG GEAR WARNING WITHOUT LOWERING THE WHEELS. WE WERE CLRED TO 3000 FT AND GIVEN A HDG FOR A RADAR BASE LEG; STILL ABOVE LNDG GEAR OPERATING SPD. ALL THE WHILE WE HAD TO SIT THROUGH A CONTINUOUSLY RINGING LEVEL III ALERT. SINCE THE R SEAT RADAR ALTIMETER WAS INDICATING PROPERLY; WE ATTEMPTED TO SWITCH THE FLT DIRECTOR TO THE FO'S SIDE. DUE TO THE FOLLOWING; WE NEVER COMPLETED THIS TRANSITION. AS THE DSCNT CONTINUED; THE FLT WARNING COMPUTER ADDED THE AURAL WARNING 'TOO LOW GEAR.' ABOUT THIS TIME WE WERE GIVEN A HDG TO INTERCEPT THE ILS FINAL WHILE STILL DSNDING TO 3000 FT. THE VECTOR PUT US RIGHT OVER BKL (BURKE LAKEFRONT). IT WAS AT THIS TIME THE TCASII ADDED 'TFC; TFC.' AS I WAS LOOKING FOR THE TFC; I HAD TO COMPETE WITH A CONTINUOUS LEVEL III ALERT CHIME; 'TOO LOW GEAR' AURAL ALERT AND NOW THE AURAL TCASII TFC ALERT. AGAIN; NONE OF THESE WARNINGS CAN BE SILENCED. SOMEWHERE IN ALL OF THIS WE WERE GIVEN A FREQ CHANGE TO CLE TWR. I DELAYED CHANGING FREQS AND LOOKED FOR THE TFC. SINCE WE WERE RIGHT OVER BKL; I ASSUMED THAT OUR DSNDING VECTOR; COUPLED WITH THE CLBING VECTOR OF A LIGHT PLANE; TAKING OFF FROM BKL; WAS GENERATING THE TFC ALERT. I DIDN'T REALLY EXPECT TO SEE A SERIOUS CONFLICT. SURE ENOUGH; THERE WAS A SINGLE ENG HIGH WING ACFT IN A L CLBING TURN. I CALLED OUT 'TFC IN SIGHT' ABOUT THE TIME THE TCASII STARTED CALLING; 'CLB; CLB.' THE PF FOLLOWED THE TCASII GUIDANCE AND WE NARROWLY MISSED THIS ACFT. SOMEWHERE IN THIS SEQUENCE THE LNDG GEAR ALERTS ENDED. STILL ON APCH CTL'S FREQ; I ANNOUNCED 'WE ARE MANEUVERING FOR AN RA.' THEIR RESPONSE WAS 'I JUST GOT HIM.' I CHANGED TO TWR AND THE REST OF THE APCH AND LNDG WAS NORMAL. PROBABLY BECAUSE OF ALL THE INTERFERENCE AND THE DELAY CHANGING FREQS I DIDN'T EVEN THINK ABOUT DECLARING A NEAR MISS. AS I REPLAY THESE EVENTS; A COUPLE OF THINGS BOTHER ME: 1) THE PF SHOULD ALWAYS FOLLOW TCASII GUIDANCE. I 'SAW' WHAT I EXPECTED TO SEE -- AN ACFT CLBING OUT OF BKL. IT TOOK ME AN EXTRA SECOND TO REALIZE THIS ACFT WAS NOT IN THE TFC PATTERN BUT AN IMMEDIATE CONFLICT. IN THE SHORT TIME IT TOOK ME TO REALIZE WE NEEDED TO TAKE ACTION TO AVOID A COLLISION; I COMMUNICATED TO THE PF THAT I HAD THE ACFT IN SIGHT. HE COULD HAVE INTERPED THIS TO MEAN THERE'S NO IMMEDIATE CONFLICT. THERE WAS NO TIME FOR ANY HESITATION; HAD HE NOT FOLLOWED THE TCASII GUIDANCE I THINK WE WOULD HAVE HIT THE OTHER ACFT. WHAT I SHOULD HAVE SAID WAS 'TFC IN SIGHT; FOLLOW THE TCASII;' AND HE SHOULD HAVE RESPONDED 'FOLLOWING THE TCASII.' THIS WOULD HAVE ALLOWED ME TO KEEP MY EYES OUTSIDE AND KNOW THAT THE PF WAS MANEUVERING TO AVOID THE TFC. IF HE DID NOT RESPOND I WOULD HAVE HAD TO TAKE CTL OF THE ACFT; THERE WASN'T TIME FOR ANY OTHER RESPONSE. 2) ALERTS THAT CANNOT BE SILENCED COUNTER EFFECTIVE COCKPIT COM. CLRLY; THE ENGINEERS WANT THE PLT TO UNDERSTAND THE IMPORTANCE/DANGER OF A PARTICULAR SIT BUT WHAT ABOUT ERRONEOUS ALERTS OR COMPOUNDED ALERTS. YOU NEED TO BE ABLE TO COMMUNICATE TO TAKE CARE OF PROBS. MAYBE IF THESE TYPES OF ALERTS COULD BE SILENCED EVEN FOR 30-60 SECONDS IT WOULD ALLOW A CREW TO BETTER COORDINATE THEIR ACTIONS. IF I HAD IT TO DO OVER AGAIN; I WOULD DO THE FOLLOWING: 1) IF SWITCHING FLT DIRECTORS DIDN'T CANCEL THE LNDG GEAR ALERT; I WOULD HAVE SLOWED AND PUT THE GEAR DOWN. 2) GIVE THE PF AN ACTION COMMAND BEFORE ANNOUNCING I HAD THE TFC IN SIGHT (IE; 'CLB' OR 'FOLLOW THE TCASII' THEN 'TFC IN SIGHT.'). HOPEFULLY; THIS WOULD ELIMINATE THE POSSIBILITY OF MISCOM DURING A CRITICAL PHASE OF FLT. 3) DECLARE AN NMAC. IT IS NOT MY INTENT TO GET ANYONE IN TROUBLE BUT A FORMAL INVESTIGATION MAY HIGHLIGHT AN ATC LOOPHOLE OR CLR UP A PLT MISCONCEPTION.