B767 Undifferentiated or Other Model
Distraction; Situational Awareness; Troubleshooting
Aircraft Equipment Problem Critical
Aircraft Equipment Problem Dissipated; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft
Control check on the ground was normal. Sometime after takeoff and during cruise climb the Captain noticed a rolling moment and an unusual amount of rudder needed. Brought up the status page on EICAS and noticed the right inboard aileron position above the neutral index. During turns; noticed that the right inboard aileron would move up for right turns; but would not move down for left turns. The other ailerons were behaving normally. Being the Relief Pilot for this flight; I was elected to go back and visually check the control surfaces. Visual check confirmed the right inboard aileron was 'stuck' about 6 inches above the faired position in level flight. During turns; the aileron would move up; but not down below the 6 inches elevated position. Conferred with Maintenance and Dispatch and decided to declare an emergency and return to the departure airport. We took our time returning to burn excess fuel in order to land under maximum landing weight. We didn't find any checklist that dealt specifically with our problem; so we consulted several checklists; took information from those that was pertinent; and used our collective experience and judgment to preclude any further problems. We descended early to help burn fuel and configured early to determine any negative effects the stuck aileron might have on controllability. Captain decided to land with flaps at 20 due to the gusty winds reported and to have higher airflow over the other ailerons for controllability. The approach and landing was uneventful. Landing weight was approximately 315;000 lbs. Sometime after touchdown the right inboard aileron moved back to its normal 'drooped' position for the flap 20 setting. Conferred with Maintenance and was told to leave flaps in the landing configuration for taxi-in. All things considered; I believe this incident was handled appropriately and professionally. The only unanticipated issue was getting the GROUND PROX. warning for landing with Flaps 20.
The 767 has two sets of ailerons and the outboard set 'locks out at speeds above 280 KTS.' Above that speed in a normal Takeoff and initial climb; it was noticed that left aileron trim was required for level flight. EICAS flight control display showed that our inboard ailerons were set in an unusual position. We did some shallow banks to verify that right inboard aileron seemed to be jammed or restricted; the left inboard moving freely and correctly. We consulted our QRH handbook and found that none of the checklists completely covered this situation; but we would reference 3 different checklists for direction/suggestions that could affect us as we eventually slowed and configured for landing.We took guidance from the Structural Damage/Controllability Checklist in being very conservative in beginning the configuration process to guard against issues we might not totally understand yet. The goal was to be fully configured at yeast 10 miles from the airport over an unpopulated area. Being conservative now was driving our final decisions. With that in mind; we verified minimum required landing distance from our Non-Normal Configuration Landing Distance tables and verified that the longest runway had ample length. We decided that a 20 vs 30 flap landing with extra speed over 20 V-REF would give us the most airspeed for control and less drag. Controls worked very well through out the landing process and really was only different in that we had more aileron trim at slower speeds than higher speeds; but still not extreme. Touchdown and roll out was nominal and a normal exit and taxi to gate would follow.
A B767 right inboard aileron remained deployed about six inches up in level flight which required unusual trim so an emergency was declared and the flight returned to the departure airport.