Narrative:

I was the PF during approach with the right autopilot on and the aircraft unexpectedly and abruptly turned right with approximately 5 degrees of heading change and up to 5 degrees of bank before the autopilot corrected back to wings level flight. This occurred when flaps were selected from 1 to 5; speed brake lever was approximately 2/3 extended; the aircraft was slowing from 210 to 190 with auto throttles on and right autopilot engaged in flch descent and LNAV modes. The EICAS status page displayed an asymmetric condition between the inboard ailerons. The left inboard aileron indicated normal droop for the flaps 5 configuration while the right inboard aileron was near full scale down deflection. The engines were providing symmetrical thrust; rudder trim was neutral and flight weather conditions were not a factor (calm; steady state winds; no wake turbulence suspected). As the autopilot leveled off and speed brakes were stowed; the asymmetrical aileron condition persisted. As soon as the autopilot was disconnected; the aircraft wanted to turn right and required approximately 2 units of left wing down aileron trim to maintain wings level. My role changed to pm at this point and the autopilot and auto throttles remained off the remainder of the flight. This aircraft state persisted and remained constant through configuration to an otherwise uneventful landing with flaps 25. After maintenance released the aircraft back to us; I was the PF for the flaps 5 takeoff. I turned on the right autopilot passing 1500 afe. All conditions were normal until the aircraft accelerated above the flaps 5 maneuver speed and flaps 1 was selected; then the flight control anomaly reappeared; I disconnected the right autopilot and engaged the left autopilot with the same result; so I disconnected the left autopilot. The asymmetry disappeared when flaps reached 1 and also with flaps up. During the subsequent approach I was the pm and the anomaly returned when flaps were at 5 and remained through another otherwise uneventful flaps 25 landing.a malfunction within the aircraft flight control system on [this specific aircraft]. What is concerning to me is that the maintenance checks and tests performed could not identify or isolate the malfunction. Provide maintenance with a more advanced and updated electronic/hydraulic flight control check.

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Original NASA ASRS Text

Title: B767 First Officer reported inboard aileron asymmetry when selecting flaps 5 on approach. Maintenance released the aircraft back to the flight crew and they experienced the same anomaly on the subsequent flaps 5 takeoff.

Narrative: I was the PF during approach with the right autopilot on and the aircraft unexpectedly and abruptly turned right with approximately 5 degrees of heading change and up to 5 degrees of bank before the autopilot corrected back to wings level flight. This occurred when flaps were selected from 1 to 5; speed brake lever was approximately 2/3 extended; the aircraft was slowing from 210 to 190 with auto throttles on and right autopilot engaged in FLCH descent and LNAV modes. The EICAS Status page displayed an asymmetric condition between the inboard ailerons. The left inboard aileron indicated normal droop for the flaps 5 configuration while the right inboard aileron was near full scale down deflection. The engines were providing symmetrical thrust; rudder trim was neutral and flight weather conditions were not a factor (calm; steady state winds; no wake turbulence suspected). As the autopilot leveled off and speed brakes were stowed; the asymmetrical aileron condition persisted. As soon as the autopilot was disconnected; the aircraft wanted to turn right and required approximately 2 units of left wing down aileron trim to maintain wings level. My role changed to PM at this point and the autopilot and auto throttles remained off the remainder of the flight. This aircraft state persisted and remained constant through configuration to an otherwise uneventful landing with flaps 25. After maintenance released the aircraft back to us; I was the PF for the flaps 5 takeoff. I turned on the right autopilot passing 1500 AFE. All conditions were normal until the aircraft accelerated above the flaps 5 maneuver speed and flaps 1 was selected; then the flight control anomaly reappeared; I disconnected the right autopilot and engaged the left autopilot with the same result; so I disconnected the left autopilot. The asymmetry disappeared when flaps reached 1 and also with flaps up. During the subsequent approach I was the PM and the anomaly returned when flaps were at 5 and remained through another otherwise uneventful flaps 25 landing.A malfunction within the aircraft flight control system on [this specific aircraft]. What is concerning to me is that the maintenance checks and tests performed could not identify or isolate the malfunction. Provide maintenance with a more advanced and updated electronic/hydraulic flight control check.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.