T6A Texan II / Harvard II (Raytheon)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 1027; Flight Crew Total 18707; Flight Crew Type 12017
Human-Machine Interface; Troubleshooting
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem; Flight Crew Returned To Departure Airport
Aircraft
While holding over ZZZ on an instrument training flight; I felt a significant left yaw and noticed the 'ball' deflect fully to the right. I asked the student if he were applying left rudder; and he told me that he was not. I took the flight controls from the student and noticed that I had to put in significant rudder pressure to center the 'ball.' I opened my emergency procedures checklist to the runaway trim procedure; and executed those emergency procedures. I contacted Approach; told them that I had a flight control malfunction; and asked to go back to the base. On the way I climbed to 7;000 MSL; and performed a controllability check. The airplane was controllable with heavy rudder pressure down to our final approach speed; so I elected to land. The landing was uneventful.
While on training flight the student and instructor aboard a Beech Texan II encountered un-commanded rudder displacement that they could not trim out but could overcome with pedal pressure. They returned to their departure airport and landed uneventfully.