AN ATR42 ON APCH AT 7000 FT DECLARED AN EMER DUE TO SMOKE AND ELECTRICAL ODOR IN THE COCKPIT CAUSED BY A FAILED WX RADAR T-R UNIT LOCATED IN A COMPARTMENT UNDER THE COCKPIT FLOOR.

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FLT HAD 18 PAX AND CREW OF 3 ONBOARD. APPROX 16 MI NE OF ORD WE WERE BEING VECTORED FOR THE ILS RWY 22R ON DOWNWIND AT 7000 FT; WHEN WE BEGAN TO SMELL SMOKE IN THE COCKPIT. WE SELECTED THE #1 BLEED VALVE OFF; BUT THE SMOKE CONTINUED TO WORSEN. WE WERE UNABLE TO IDENT THE SOURCE OF THE SMOKE BUT AGREED THAT IT WAS PROBABLY ELECTRICAL IN NATURE. WE PUT OUR OXYGEN MASKS ON AND I CALLED THE FLT ATTENDANT. SHE RPTED NO SMOKE IN THE CABIN FROM HER JUMP SEAT IN THE AFT OF THE ACFT. AS THE FO WENT THROUGH THE ELECTRICAL SMOKE CHKLIST; I NOTIFIED APCH CTL OF OUR PROB; AND WAS GIVEN A TURN TOWARD RWY 22R. WE LANDED ON RWY 22R IN MODERATE RAIN; WITH THE CFR EQUIP STANDING BY. IN COMMUNICATING WITH THE FLT ATTENDANT; SHE SAID IT WAS NOT POSSIBLE TO UNDERSTAND US 90% OF THE TIME WITH OUR OXYGEN MASKS ON. WHEN I REMOVED MY OXYGEN MASK TO TALK TO HER ON THE HAND-MIKE VIA THE SPEAKER; THERE WAS TOO MUCH FEEDBACK FROM THE OXYGEN MASK MIKE FOR US TO COMMUNICATE. I ORDERED AN EVAC AT THIS POINT VIA THE PA SYS. I ALSO BELIEVE THE WINDSHIELD WIPER SYS TO HAVE BEEN A FACTOR. THE ATR WIPER SYS IS BARELY ADEQUATE UNDER IDEAL CIRCUMSTANCES. AT NIGHT; WITH NO LNDG OR TAXI LIGHTS (DUE TO NO AC WILD ELECTRIC PWR); THE WIPER WAS TOTALLY USELESS. I WAS UNABLE TO SEE THE RWY CTRLINE OR TXWYS TO CLR THE RWY. THE FO ALSO INFORMED ME AFTER THE INCIDENT; THAT DURING HIS TRAINING HE HAD NEVER DONNED THE OXYGEN MASK; DID NOT UNDERSTAND HOW TO USE THE INTERCOM WITH IT ON; AND HAD NEVER OPENED THE COCKPIT EMER EXIT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE SMOKE AND ELECTRICAL ODOR WAS CONFINED TO THE COCKPIT AND THE CAUSE WAS A FAILED OR SHORTED WX RADAR T-R UNIT LOCATED IN A COMPARTMENT UNDER THE COCKPIT FLOOR. THE RPTR SAID MAINT WAS NOT FORTH COMING WITH ANY DETAILS AND THE UNION WAS THE SOURCE OF THE INFO ON THE FAILED RADAR UNIT. CALLBACK CONVERSATION WITH RPTR ON ACN 430317 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE SMOKE WAS NOT RPTED BY MAINT BUT DID GET SOME DETAILS FROM A MECH WHO ADVISED A RADAR UNIT LOCATED UNDER THE COCKPIT FLOOR FAILED. THE RPTR SAID A QUICK SCAN OF THE CIRCUIT BREAKERS DID NOT REVEAL ANY TRIPPED BUT IT WAS ONLY A QUICK CHK AND A BREAKER COULD HAVE EASILY BEEN MISSED.