B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 1144
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification
Aircraft
Passing approximately FL240 while descending into [destination] deployed speedbrakes to acquire the VNAV path. As soon as handle came out of detent aircraft rolled sharply left [and the] autopilot corrected with one unit of right aileron. AUTO SPEEDBRAKE EICAS message also displayed immediately. Stowed handle and aircraft rolled back to the right until the ailerons returned to neutral; then aircraft flew level. Redeployed speedbrakes with same response. Amount of speedbrakes handle made no difference in roll; stayed at one unit all the way to full speedbrakes. Disconnected autopilot when descending through FL190 and reattempted use of speedbrakes with the same results. Engaged center autopilot but had the same conditions so reengaged the left autopilot. Anytime the speedbrake handle was moved out of the down detent aircraft rolled left and autopilot added one unit right aileron to maintain wings level. Elected to keep speedbrake use to a minimum. Disconnected autopilot descending through 11000 feet as I wasn't comfortable with leaving it engaged with a possible flight control issue. Aircraft never rolled any of the times I hand-flew; seemed perfectly in trim.Received a request from ATC to slow from 250 to 190 knots for slowing traffic. FO had already run through the Auto Speedbrake QRH procedure which admonished not to arm the speedbrakes for landing. I advised that we should be ready for possible roll issues as flaps were extended and called for flaps 1. No issues at the setting. I called for flaps 5 and started to get some left rolling without the speedbrakes being deployed. We had just checked on with Tower and notified them of our intentions. With flaps 30 roll was much more pronounced; requiring as much as 4 units of right aileron to maintain wings level. Winds were 250 deg at 10 knots so no crosswinds were involved. FO reminded me to use manual spoilers after touchdown. As soon as the aircraft touched down the need for right aileron disappeared. I selected reverse and the FO called 'speedbrakes'; which I then manually deployed. The rest of the landing rollout and runway exit were uneventful. ATC asked us if we needed any assistance; to which we replied no. Taxi to the gate was completed with no further issues. We elected to keep the spoilers deployed for maintenance while being aware of that in case an emergency egress situation should come up requiring their stowage.
[Report narrative contained no additional information.]
B757 flight crew reported an uncommanded roll occurred when the speed brakes were deployed and again when flaps were extended for landing.