SMT EXPERIENCES SEVERE AILERON FLUTTER AFFECTING CTL YOKE SO AILERONS UNUSABLE. BY REDUCING SPD PLT STOPS FLUTTER.

Narrative

AT THE TIME OF THE INCIDENT WE WERE IN CRUISE FLT (IAS OF 155 MPH) THE AILERONS STARTED A FLUTTER THAT WAS XMITTED TO THE CTL YOKE WHICH BRIEFLY MADE THE AILERONS UNUSABLE. THE UP AND DOWN MOVEMENT OF THE AILERONS WERE APPROX 6 INCHES. AT ONCE WE STARTED A SPD REDUCTION; THE FLUTTER STOPPED AT APPROX (125 IAS MPH). DURING POST FLT INSPECTION THE AILERON TRIM TAB ON THE L AILERON HAD BROKEN FROM ITS CONNECTING ROD. THE AILERON SHOWED SIGNS OF BUCKLING ON THE BOTTOM SIDE. A RPT WAS MADE THAT EVENING TO THE FAA. THEY ADVISED TO CALL THE LCL FSDO THE NEXT MORNING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR STATES HE HAS NEVER BEEN SO SCARED IN AN AIRPLANE. MECHS FOUND THAT THE TRIM TAB BROKE AT THE ATTACHMENT POINT THEN THE FLUTTER OCCURRED. RPTR HAD THOUGHT REVERSE HAPPENED. NOT ABLE TO FIND THE BOLT; BUT MECH BELIEVES IT BROKE WHERE IT ATTACHES TO THE ACTUATOR. ALL APPEARED NORMAL IN THE PREFLT. RPTR TALKED TO NTSB AS REQUIRED AND WAS REFERRED TO LCL FSDO. THEY DID NOT WANT TO DO ANY FOLLOW UP. HAS ASKED AROUND IF ANYONE ELSE EXPERIENCED SUCH A PROBLEM. HE IS THE ORIGINAL APPARENTLY.