Narrative:

On the arrival; about 6 miles from [zzzzz intersection]; in navigation and autopilot we noticed that the airplane was no longer tracking the course. We confirmed that we were still in navigation; so the captain pilot flying (PF) used heading mode to get us back to [zzzzz intersection]. At that instance; approach asked us; 'are you still on the arrival?' first officer first officer pilot monitoring (pm) replied that for some reason 'we had gone off course'; and we are proceeding back to [zzzzz intersection]. We saw .5R off course. After overflying [zzzzz intersection] in heading; the PF re-engaged navigation; and the aircraft flew the course from [zzzzz intersection] just fine. Soon thereafter we were given a base leg turn; which the PF executed in heading with a/P engaged. That turn; and the turn to final; were accomplished with no problems. On final; the PF disconnected the a/P and the aircraft instantly banked hard right. We executed a discontinued approach to trouble shoot the problem. Interestingly; when the flaps were retracted from 28 to 15; the problem fixed itself. During the banking incident; we noticed that the spoilers indicated up on both wings (without the expected warning that the spoilers were up with flaps extended). We re-configured and landed uneventfully. The captain followed up with maintenance and was told that the #4 and 5 spoilers on the right wing were stuck up 3 inches. We suspect that the a/P was unable to hold course on the arrival due to the aircraft pulling right with no indications in the cockpit.

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Original NASA ASRS Text

Title: MD-11 Captain reported autopilot unable to maintain correct track in NAV Mode due to right wing spoilers being permanently slightly deployed.

Narrative: On the arrival; about 6 miles from [ZZZZZ Intersection]; in NAV and AUTOPILOT we noticed that the airplane was no longer tracking the course. We confirmed that we were still in NAV; so the Captain Pilot Flying (PF) used HDG mode to get us back to [ZZZZZ Intersection]. At that instance; Approach asked us; 'Are you still on the arrival?' FO First officer Pilot Monitoring (PM) replied that for some reason 'we had gone off course'; and we are proceeding back to [ZZZZZ Intersection]. We saw .5R off course. After overflying [ZZZZZ Intersection] in HDG; the PF re-engaged NAV; and the aircraft flew the course from [ZZZZZ Intersection] just fine. Soon thereafter we were given a base leg turn; which the PF executed in HDG with A/P engaged. That turn; and the turn to final; were accomplished with no problems. On final; the PF disconnected the A/P and the aircraft instantly banked hard right. We executed a discontinued approach to trouble shoot the problem. Interestingly; when the flaps were retracted from 28 to 15; the problem fixed itself. During the banking incident; we noticed that the spoilers indicated up on both wings (without the expected warning that the spoilers were up with flaps extended). We re-configured and landed uneventfully. The Captain followed up with Maintenance and was told that the #4 and 5 spoilers on the right wing were stuck up 3 inches. We suspect that the A/P was unable to hold course on the arrival due to the aircraft pulling right with no indications in the cockpit.

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.