EMBRAER 145RJ CREW EXPERIENCED 'TAIL FLUTTER' ON DSCNT FROM 8000 FT TO 3000 FT AT 250 KTS.

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TAIL FLUTTER FROM 8000 FT TO 3000 FT MSL; 250 KTS. HARMONIC VIBRATION THROUGH ACFT. NOT CONTINUOUS; COMES IN 'WAVES.' CAN BE AGGRAVATED BY THE PLTS WITH PULLING UP ON YOKE (NOSE UP) AND RELEASING PRESSURE. VORTEX GENERATORS HAVE BEEN INSTALLED ON HORIZ STABILIZER. THIS DOES NOT CORRECT THE PROB BUT DOES REDUCE SEVERITY. CONCERN: METAL FATIGUE DUE TO VIBRATION AND MOVEMENT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT RPTS THAT THE ACFT IS AN EMBRAER 145RJ WITH AN ACFT VIBRATION OR BUFFET. HE RPTS THAT ALL ACFT IN HIS ACR FLEET ARE AFFECTED; SOME MORE THAN OTHERS. THE FOLLOWING AFFECT THE VIBRATION: PUTTING BACK PRESSURE ON THE YOKE AND THEN RELEASING WILL TRIGGER IT; TURNING ON THE AIRFOIL THERMAL ANTI-ICE WILL CAUSE IT TO STOP. THE RPTR ALSO STATED THE TAIL EXHAUST FOR THE STABILIZER LEADING EDGE IS JUST AHEAD OF THE ELEVATOR OUTBOARD AERODYNAMIC BAL; THUS AFFECTING AIRFLOW OVER THE ELEVATOR. THE MANUFACTURER HAS INSTALLED VORTEX GENERATORS IN THIS SAME AREA. THIS REDUCES THE VIBRATION BUT DOES NOT ELIMINATE IT. THERE IS STILL ENOUGH VIBRATION THAT THE PLT IS CONCERNED WITH FATIGUE LIFE. THE CREWS AT THIS ACR HAVE BEEN LISTING THE PROB IN THE ACFT LOG; HOWEVER; MAINT DOES NOTHING TO FIX THE PROB. THE PLT FLEW A 'TEST FLT' WITH THE MANUFACTURER'S ENGINEERING PERSONNEL ABOARD. THEY HAD INSTRUMENTED THE ACFT; BUT HE DOES NOT KNOW THE OUTCOME OF THE TEST.