Narrative:

IFR from grr to C52, ceiling 2000-2500 ft MSL, visibility 2-3 SM. Aircraft has advanced aeronautical safety low thrust detectors (ltd) installed (stc SA100 7 northwest). While being vectored to intercept VOR 29 at 2600 ft MSL, audible and visual alarms went off, indicating failure of right engine. Applied full mixture, propeller, throttle to both engines. Left engine audible and visual alarms went off. Declared emergency with mke approach. RPM, manifold pressure, fuel flow all normal. Checked ltd switch, moved to heat position. Within a few seconds, ltd alarms stopped. System normal. Informed ATC emergency resolved. Requested vectors to ILS runway 4 at rac. Uneventful landing and canceled flight plan. Called mke approach at their request. Explained above. Conclusion: ice had blocked both ltd pitots. Add heater switch to takeoff and landing checklist. Callback conversation with reporter revealed the following information: reporter states that the ltd unit is a pitot tube installed on the downstream side of each propeller. It measures the balance of air on both engines and if there is a change of engine 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 position switch to operate the system. The center position activates the ltd, the down position removes the audible alarm when one might want it off, for taxi or maneuvering, and the up position activates pitot heat. This up position should be used at any time when in visible moisture just as the normal pitot heat would be used. As soon as the up position was selected the ice was cleared and the alarms stopped. Reporter had already declared an emergency so approach did want to speak to him. Once the incident was explained there was no further action.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

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.