What was found
DURING A POST CHECK FLIGHT, IT WAS REPORTED THAT ON CLIMB, NOTICED THE AIRPLANE TOOK APPROXIMATELY 2 UNITS LWD AILERON TO MAINTAIN HEADING. AFTER LEVELING AT 15,000, NOTICED AIRFRAME VIBRATION THAT WAS MORE THAN USUAL. EXTENDED THE FLAPS AND NOTICED THE AIRPLANE REQUIRED MORE RUDDER TRIM WITH EACH INCREASING DEGREE OF FLAP EXTENSION. AT FLAPS 10 DEGREE, RUDDER WAS 2.5 UNITS LT TO MAINTAIN HEADING WITH AILERON AT .4 UNITS LWD. MAINTENANCE FOUND RIGHT WING UPPER INBOARD PANEL 651AT, MISSING DURING A POST FLIGHT WALKAROUND, REPLACED THE PANEL IAW AMM 20-50-11.