Gulfstream G200 (IAI 1126 Galaxy)
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 156; Flight Crew Total 6200; Flight Crew Type 1300
Aircraft Equipment Problem Critical
Aircraft Equipment Problem Dissipated; Flight Crew Diverted; Flight Crew Landed As Precaution; General Declared Emergency
Aircraft
In cruise flight at FL410; we noticed the aileron miss-trim flag display on the PFD. The amber flag flashed for a few seconds and then went away; it returned again a few seconds later but remained and turned to the red. I attempted to input some roll trim to correct the problem but I noticed the roll trim indicator on the EICAS did not move in either direction. At this point I elected to disconnect the autopilot (AP) in order to determine if the AP was masking the aircraft being in an out of trim situation. When I disconnected the AP the airplane immediately began a slow roll to the left; I attempted to roll the airplane back to level flight at which time discovered I had very little to no roll input. I was able to roll the wings level but found it very difficult to keep the wings from rocking with increased oscillation. We determined there was an abnormal situation with what felt very much like a jammed aileron condition. We declared an emergency and began our descent and diversion. The aileron condition continued until about 12;000 FT at which time I noticed some increasing roll control; this continued until approximately 8;000 FT at which time normal; full roll control returned. This was a gradual return from the jammed condition to the return of normal functioning of the ailerons. We landed without incident and conducted a complete flight control and trim function control check prior to engine shutdown. No abnormal indications were noted or felt with either system. As the events unfolded we did run the Jammed Aileron QRH checklist. We discussed the option of pulling the Roll disconnect handle. I elected to not pull the handle as I had limited but enough roll control; to maintain a wings level and stabilized descent flight condition. I knew what I had with the current flight control situation and did not want to go into an unknown condition by pulling the handle until such time it was absolutely necessary due to complete loss of roll control and the deterioration of stabilized flight. We were alert to any changes in our flight condition and constantly communicated our primary descent and approach activities and parameters to ensure all mandatory functions were carried out in the safest and most efficient manner.
The reporter was told by Maintenance that the elevator feel spring was likely the cause of the aileron jam at FL410. Maintenance indicated that the feel spring unit is mounted in the belly of the aircraft and it is thought that a galley or lavatory leak may have provided water that got into the unit and froze at high altitude.
G200 Captain experiences jammed or frozen aileron controls at FL410 and elects to divert to a suitable airport. During descent roll control begins to return passing 12;000 FT and is completely normal by 8;000 FT. An uneventful landing ensues.