Narrative:

The first officer was flying the ILS runway 27L at sbn. We were at about 1000 ft AGL. The aircraft had accumulated about 1/2 inch to 3/4 inch of mixed ice. I activated the deice boots in the single deice mode. The single mode should inflate the outboard wings for 6 seconds and then the inboard and tail for 6 seconds. Inflation of the boots is indicated by a green annunciator in the cockpit. When the boots were activated the tail deice light remained illuminated. Because the other boots had deflated normally and were visually checked as deflated, we assumed that it was a false light and that the tail boot was deflated. Rather than climbing back into the ice with a system that was not fully functional, we continued. We also made the assumption that the ice may or may not have been removed so our reference speed was increased by 10 KTS. The landing was completed with full flaps. During final approach, the deice boots were cycled repeatedly in the single and manual modes, however, the tail light remained illuminated. No adverse flying affects were noticed, and after landing visual inspection indicated no significant ice on the tail. The green light extinguished about 90 seconds after both engines were shut down. A mechanic inspected the system. He found that moisture in the electric line and or switch caused the false indication. No FARS were broken (to the knowledge of the crew) nor was any priority handling given. Callback conversation with reporter revealed the following information: aircraft is a BE02.

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Original NASA ASRS Text

Title: A BE02 COMMUTER FLC CONTINUED AN APCH AND LNDG IN ICING CONDITIONS AFTER RECEIVING AN ANNUNCIATOR THAT INDICATED THAT THERE MIGHT BE A PROB WITH THE DEICE SYS. POST FLT MAINT INSPECTION FOUND THAT MOISTURE IN THE SWITCH HAD CAUSED THE FALSE INDICATION.

Narrative: THE FO WAS FLYING THE ILS RWY 27L AT SBN. WE WERE AT ABOUT 1000 FT AGL. THE ACFT HAD ACCUMULATED ABOUT 1/2 INCH TO 3/4 INCH OF MIXED ICE. I ACTIVATED THE DEICE BOOTS IN THE SINGLE DEICE MODE. THE SINGLE MODE SHOULD INFLATE THE OUTBOARD WINGS FOR 6 SECONDS AND THEN THE INBOARD AND TAIL FOR 6 SECONDS. INFLATION OF THE BOOTS IS INDICATED BY A GREEN ANNUNCIATOR IN THE COCKPIT. WHEN THE BOOTS WERE ACTIVATED THE TAIL DEICE LIGHT REMAINED ILLUMINATED. BECAUSE THE OTHER BOOTS HAD DEFLATED NORMALLY AND WERE VISUALLY CHKED AS DEFLATED, WE ASSUMED THAT IT WAS A FALSE LIGHT AND THAT THE TAIL BOOT WAS DEFLATED. RATHER THAN CLBING BACK INTO THE ICE WITH A SYS THAT WAS NOT FULLY FUNCTIONAL, WE CONTINUED. WE ALSO MADE THE ASSUMPTION THAT THE ICE MAY OR MAY NOT HAVE BEEN REMOVED SO OUR REF SPD WAS INCREASED BY 10 KTS. THE LNDG WAS COMPLETED WITH FULL FLAPS. DURING FINAL APCH, THE DEICE BOOTS WERE CYCLED REPEATEDLY IN THE SINGLE AND MANUAL MODES, HOWEVER, THE TAIL LIGHT REMAINED ILLUMINATED. NO ADVERSE FLYING AFFECTS WERE NOTICED, AND AFTER LNDG VISUAL INSPECTION INDICATED NO SIGNIFICANT ICE ON THE TAIL. THE GREEN LIGHT EXTINGUISHED ABOUT 90 SECONDS AFTER BOTH ENGS WERE SHUT DOWN. A MECH INSPECTED THE SYS. HE FOUND THAT MOISTURE IN THE ELECTRIC LINE AND OR SWITCH CAUSED THE FALSE INDICATION. NO FARS WERE BROKEN (TO THE KNOWLEDGE OF THE CREW) NOR WAS ANY PRIORITY HANDLING GIVEN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ACFT IS A BE02.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.