PLT OF BE55 HAS LTD ACTIVATE ON APCH. BOTH AUDIBLE AND VISUAL ALARMS ACTIVATED BUT WHEN THE SYS HEAT POS WAS SELECTED THE ALARMS STOPPED.

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IFR FROM GRR TO C52; CEILING 2000-2500 FT MSL; VISIBILITY 2-3 SM. ACFT HAS ADVANCED AERO SAFETY LOW THRUST DETECTORS (LTD) INSTALLED (STC SA100 7 NW). WHILE BEING VECTORED TO INTERCEPT VOR 29 AT 2600 FT MSL; AUDIBLE AND VISUAL ALARMS WENT OFF; INDICATING FAILURE OF R ENG. APPLIED FULL MIXTURE; PROP; THROTTLE TO BOTH ENGS. L ENG AUDIBLE AND VISUAL ALARMS WENT OFF. DECLARED EMER WITH MKE APCH. RPM; MANIFOLD PRESSURE; FUEL FLOW ALL NORMAL. CHKED LTD SWITCH; MOVED TO HEAT POS. WITHIN A FEW SECONDS; LTD ALARMS STOPPED. SYS NORMAL. INFORMED ATC EMER RESOLVED. REQUESTED VECTORS TO ILS RWY 4 AT RAC. UNEVENTFUL LNDG AND CANCELED FLT PLAN. CALLED MKE APCH AT THEIR REQUEST. EXPLAINED ABOVE. CONCLUSION: ICE HAD BLOCKED BOTH LTD PITOTS. ADD HEATER SWITCH TO TKOF AND LNDG CHKLIST. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THE LTD UNIT IS A PITOT TUBE INSTALLED ON THE DOWNSTREAM SIDE OF EACH PROP. IT MEASURES THE BAL OF AIR ON BOTH ENGS AND IF THERE IS A CHANGE OF ENG THRUST IT GIVES AN ALARM; A LIGHT AND AN AUDIBLE WARNING. THERE ARE 2 STAGES OF THE LIGHT; A YELLOW AND THEN RED INDICATION. THERE IS A 3 POS SWITCH TO OPERATE THE SYS. THE CTR POS ACTIVATES THE LTD; THE DOWN POS REMOVES THE AUDIBLE ALARM WHEN ONE MIGHT WANT IT OFF; FOR TAXI OR MANEUVERING; AND THE UP POS ACTIVATES PITOT HEAT. THIS UP POS SHOULD BE USED AT ANY TIME WHEN IN VISIBLE MOISTURE JUST AS THE NORMAL PITOT HEAT WOULD BE USED. AS SOON AS THE UP POS WAS SELECTED THE ICE WAS CLRED AND THE ALARMS STOPPED. RPTR HAD ALREADY DECLARED AN EMER SO APCH DID WANT TO SPEAK TO HIM. ONCE THE INCIDENT WAS EXPLAINED THERE WAS NO FURTHER ACTION.