A CE550 EXPERIENCED CTL YOKE VIBRATION AFTER DEPARTING WITH CONTAMINATION ON THE HORIZ STABILIZER. THE FLT RETURNED TO LAND.

Narrative

ON FEB/WED/07; AT ZZZ THERE WAS A SNOWSTORM IN WHICH OUR ACFT WAS NOT ABLE TO BE PUT IN A HANGAR. THAT EVENING THE CAPT WAS BRIEFED FOR A TRIP FOR FEB/THU/07. HE HAD ME CALL THE FBO TO TRY TO GET IT INTO A HANGAR; AND I WAS TOLD IT WOULD BE PUT INTO A HANGAR. ON THE MORNING OF FEB/THU/07; WE GOT TO THE ACFT WHICH WAS ALREADY OUTSIDE THE HANGAR. I ASKED LINE PERSONNEL IF IT HAD BEEN IN THE HANGAR ALL NIGHT? THEY SAID 'YES.' THE CAPT DID ALL THE INTERIOR AND EXTERIOR PREFLT DUTIES BECAUSE I WAS IN TRAINING FOR CAPT. THE ACFT WAS SPOTLESS; DRY; AND SHOWING NO EVIDENCE OF ANY CONTAMINATION AT ALL. WE DEPARTED WITH NOTHING UNUSUAL. AFTER CLBING THROUGH TURB AT ABOUT 5000 FT I NOTICED A SLIGHT BUFFET IN THE YOKE AND HAD HIM FEEL IT. WE DECIDED TO RETURN TO ZZZ. I ELECTED TO GET FULLY CONFIGURED AT A HIGHER ALT INSTEAD OF DOING IT AT PATTERN ALT AND WHEN FLAPS WERE SELECTED TO 15 DEGS THE BUFFET WENT AWAY. I MADE A NORMAL LNDG. WHEN THE ACFT WAS BROUGHT INTO A HANGAR A MECH STOOD ON A LADDER AND SAW THAT THERE WAS SOME CONTAMINATION ON THE HORIZ STABILIZER. IT IS MY BELIEF THAT THE ACFT WINGS WERE SWEPT OFF PRIOR TO BEING PUT INTO THE HEATED HANGAR THE NIGHT BEFORE AND AS SOON AS THE WINGS WERE CLEAN IT WAS PUSHED OUTSIDE. MY COMPANY HAS NO POLICY FOR THIS SITUATION AND HOPEFULLY THAT WILL CHANGE. ALSO THE MANUFACTURER'S CHKLIST DOES NOT EITHER.