FLT DIVERTED DUE TO AN ERRONEOUS GEAR WARNING INDICATION.

Narrative

AFTER NORMAL TKOF GEAR WAS SELECTED UP. AFTER GEAR RETRACTION THE L MAIN INDICATED THAT IT WAS NOT LOCKED UP. A RED 'UNLOCK' LIGHT WAS ILLUMINATED. WE EXECUTED THE CHKLIST PROC ON CLBOUT FROM CVG. WE LOWERED THE GEAR AND RECEIVED 3 GREEN DOWN AND LOCKED. WE THEN RAISED THE GEAR AND STILL THE L MAIN SHOWED NOT LOCKED IN UP POS. WE CONTACTED COMPANY MAINT CTL. THEY HAD US CONTINUE THE FLT; BUT DIVERT TO PITTSBURGH. (THE CHKLIST AUTH CONTINUED FLT. IN PIT OUR MAINT PERSONNEL COULD LOOK AT THE ACFT.) WE LANDED UNEVENTFULLY. THERE WAS CONSIDERABLE ICE; SNOW; AND SLUSH ON THE TXWYS AT CVG. WE FEEL THAT THE SNOW/SLUSH COVERED UP THE 'PROXI' SENSORS ON THE MAIN GEAR. THEREFORE THE SENSORS COULDN'T TELL THAT THE GEAR WAS UP. (THIS ACFT DOES NOT USE MICRO SWITCHES; AND CONTAMINATION OF THE MAIN GEAR FROM ICE/SLUSH; ETC; HAS BEEN A PROB WITH THE DORNIER 328 BEFORE.) CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PROX SENSORS ON THE DORNIER 328 SEND INDICATION AND WARNING STATUS INFO TO THE PSEU (PROX SWITCH ELECTRONIC UNIT). THE SENSORS ARE LOCATED ON THE UPLOCKS AND DOWNLOCKS OF THE GEAR; AND ONLY 'SENSE' CONTACT DISTANCE; AS OPPOSED TO THE POSITIVE MECHANICAL MOVEMENT OF MICROSWITCHES. THE FLC RECEIVED A RED; 'NOT LOCKED IN SELECTED POS' GEAR WARNING LIGHT WHICH REQUIRED COMPLIANCE WITH A 200 KT AIRSPD LIMITATION. RPTR STATES THAT PROX SWITCHES ARE THE PRIMARY MEANS OF INDICATION AND WARNING SIGNALS ON THE D328. HE IS CONCERNED THAT THE DIVERTED FLTS (DUE TO A SENSOR RELATED PROB) CONTRIBUTE TO A LOWERED AIRLINE RELIABILITY FACTOR. THE CEO AND POI ARE APPRISED; AND THE COMPANY HAS ALERTED THE MANUFACTURER THAT THERE HAVE BEEN MANY INDICATION AND WARNING PROBS RELATED TO SNOW AND ICE ACCUMULATION. IN ORDER TO AVERT FUTURE ERRONEOUS SIGNALS; A DIRECTIVE HAS BEEN ISSUED REGARDING CREW MEMBER ASSURANCE OF GEAR AND WHEEL WELL DEICING PRIOR TO DEP.