MD-11
Flight Crew Air Transport Pilot (ATP)
Distraction; Troubleshooting; Human-Machine Interface; Workload
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation; Flight Crew Overcame Equipment Problem
Human Factors; Aircraft
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.
[Report narrative contained no additional information.]
MD-11 Captain reported autopilot unable to maintain correct track in NAV Mode due to right wing spoilers being permanently slightly deployed.