MD-11
Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Returned To Gate; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Weather; Aircraft
During flight control check the ailerons did not respond appropriately. Movement of the control yoke was not correct as the control wheel would not return to a neutral position. In other words; with full right or left aileron input the yoke would remain in that position without returning to center position being very difficult to move.  Returned to the gate and entered the information into the log book. Maintenance worked on the issue for some time.  Maintenance said that they had found some corrosion around a cannon plug that was giving info to the FCC (I believe that is what they said.) In any case; the airplane passed all the checks and was returned to service. The airplane worked well before takeoff and during all phases until the landing phase when the autopilot was turned off. The First Officer and I had discussed the situation and decided it would be a good idea to shut off the autopilot and make sure all was well. After the autopilot went to dual land the First Officer turned off the autopilot and quickly realized we were again having the same issue with poor aileron movement. I took the airplane and tested the controls. The ailerons were not responding well. We declared an emergency.  I added about 15 knots of speed and they worked better. Ref was 156 knots which put the speed about 170 knots. We briefly discussed a G/A and decided the airplane was stable and in a good position to make a safe landing. Aileron movement was very restricted.  The First Officer did an outstanding job of flying a stable approach and because of this and the lack of crosswinds we were in a good position to continue to a safe landing.  We were asked if we still needed assistance after landing; we declined and went to the gate where we wrote up the problem as well as briefed maintenance. The ailerons reacted as though we were fighting against the auto pilot.
Although nothing definite has been found; the supposition at this time is that water got into some greased bearings and froze in cruise causing the ailerons to become stiff. A long discussion was had with the Maintenance staff before releasing the aircraft to their care and the ailerons became less stiff as time passed. How the crew that flew the aircraft previously missed the stiff ailerons during landing is unknown but an autoland is a possibility.
MD11 Captain reports discovering very stiff ailerons during the control check and returns to the gate for maintenance. Maintenance finds nothing definite after several hours of checking. The hydraulics are powered up and the ailerons are found to be normal and the flight departs. All is normal until final approach when the autopilot is switched off and the ailerons are found to be nearly frozen. The approach is continued to a successful landing.