AN MDT COMMERCIAL FIXED WING ACFT DECLARED AN EMER AND DIVERTED DUE TO A SMOKE DETECTOR WARNING. THIS WARNING CAUSED AN EMER TO BE DECLARED ON THE PREVIOUS FLT OF THE DAY.

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THIS WAS TO BE OUR FINAL LEG OF THE DAY; GOING TO SGF. WE WERE SCHEDULED ON ACFT XX; ON WHICH WE HAD EARLIER THAT SAME DAY HAD TO DECLARE AN INFLT EMER DUE TO AN ELECTRICAL SMOKE WARNING. MAINT HAVING RUN THE ACFT FOR 45 MINS ON THE GND WITHOUT ANY PROBS. RETURNED THE ACFT FOR FLT. ON THIS LEG WE WERE ALSO TO BE LINE CHKED BY OUR POI; STL. WE WERE CLRED OUT OF THE GATE BY RAMP AND INSTRUCTED TO CONTACT STL METERING AT THE X1 LOCATION. AT X2 WITH HIS TAIL POINTED AT OUR TAIL WAS A B727. I WAS INSTRUCTED BY MY CAPT TO START ENG #1; HAVING TAXIED OUT ON ENG #2 ONLY. AS I WAS DOING THIS; THE B727 WAS CLRED TO TAXI TO RWY 12. THE JET BLAST FROM HIS ENGS SLAMMED OUR YOKE (ELEVATORS) VIOLENTLY FROM FULL FORWARD TO THE LOCKED POS 1/2 WAY BACK TOWARDS THE PLTS. THIS FORCE CAUSED AN ELEVATOR PITCH DISCONNECT AND THE ASSOCIATED AURAL WARNINGS. WE SUBSEQUENTLY TAXIED BACK TO OUR GATE AND NOTIFIED MAINT. THE ELEVATORS RECONNECTED; THE PAX REBOARDED; AND OUR POI RESEATED. WE ONCE AGAIN SET OFF FOR SGF. ON CLBOUT OF STL; AT APPROX 6000 FT; WE AGAIN GOT AN ELECTRICAL SMOKE WARNING. I WAS FLYING; CAPT RAN CHKLIST. HE; UPON COMPLETING THE CHKLIST; DECLARED AN EMER; REQUESTING A RETURN TO STL. HE NOTIFIED THE FLT ATTENDANTS AND HAD THEM BRIEF THE PAX. AS HAD HAPPENED EARLIER; DSNDING THROUGH APPROX 3000 FT; THE ELECTRICAL SMOKE LIGHT ON OUR CAP WENT OUT. WE LANDED WITHOUT INCIDENT AND RETURNED TO OUR GATE. SPECULATION FROM MAINT WAS THAT A SMALL OIL LEAK INTO OUR L PACK WAS CREATING ENOUGH SMOKE TO SET OFF THE OPTICAL SMOKE DETECTOR. AS OF TODAY; AUG/XA/97; I HAVE NOT HEARD A FINAL DETERMINATION AS TO WHAT EXACTLY CAUSED THIS PROB.