RVR CALL MADE WHEN EQUIP IN THE TEST MODE. CORRECTED BY THE TWR.

Narrative

WE WERE ON THE APCH; HAVING BEEN CLRED FOR AN ILS APCH -- GS OUT. THE ATIS HAD NOT MENTIONED ANYTHING ABOUT THE GS BEING OUT AND THE WX WAS WORSE THAN THE 500 FT CEILING AND 7 MI VISIBILITY BEING RPTED. WHEN WE WERE 3 MI FROM THE FINAL APCH FIX; THE TWR CTLR CALLED THE VISIBILITY 6000 PLUS RVR AND THE PREVAILING BETTER THAN 1 MI. WE WERE CLRED TO LAND. 1 MI BEFORE THE FINAL APCH FIX; THE CTLR SAID THE RVR WAS 4500; PREVAILING VISIBILITY 1 MI. THE APCH PLATE SHOWED THAT WE NEEDED 5000 RVR TO CONTINUE THE APCH SO THE CAPT ANNOUNCED OUR INTENTION TO GO MISSED APCH. THE CTLR THEN SAID 'RVR IS UNUSABLE; VISIBILITY IS 1 MI.' WE RE-INTERCEPTED THE APCH AND LANDED IN HVY RAIN. THE CAPT CALLED THE TWR BY PHONE ON THE GND AND HE WAS TOLD THAT THE RVR DEVICE WENT INTO A SELF-TEST MODE ON THE HR; WHICH HAPPENED TO BE DURING OUR APCH. THEY AGREED THAT IT WAS CONFUSING TO US IN THE COCKPIT; BUT ASSURED US THAT THE VISIBILITY WAS ABOVE MINS FOR THE APCH. THE CTLR ASSURED THE CAPT THAT NOTHING WAS INCORRECT WITH WHAT EITHER OF US DID. SUPPLEMENTAL INFO FROM ACN 221381: I WAS TOLD THAT THE RVR WENT INTO A SELF TEST MODE AT ON THE HR TO 3 MINS PAST THE HOUR. IT DOES THIS ALL THE TIME AT THAT SPECIFIC TIME OF DAY.