Narrative:

While configuring for the approach on a dog-leg to intercept the localizer xxl at ZZZ; received level 2 slat disag after extending flaps to 28. The alert initially stayed on for probably a minute and then went away. No uncommanded rolling moment. Discontinued the approach and referenced the QRH. [Notified] approach. Brought the jumpseater into the cockpit to assist and provide oversight. Called the dispatcher on satcom and requested a conference call with [maintenance control]. [Maintenance control] said datalinked telemetry from the aircraft reported a single sensor had faulted to a value of zero. I discussed and investigated the potential of an actual asymmetric slat situation vs only a sensor problem. I was satisfied with the level and depth of the information provided by [maintenance control] that [maintenance control] believed it was only a sensor problem. I ran through a decision tree of following the QRH level 2 slat disag procedure. A #1 thrust reverser MEL precondition; wet runway and poor data in the QRH procedure for landing distance with an reverser inop led me to understand that a 0RET/28 landing would probably result in stopping near the last brick of the runway. ZZZ1 was our alternate but their long runway was under construction and the runways available there were shorter than ZZZ xxr. We didn't have enough fuel to go anywhere else. After a conference with the first officer; and bringing the senior jumpseat pilot into the decision process; I decided that due to a lack of uncommanded rolling moment; the intermittent nature of the problem and the telemetry data from the aircraft; the best course of action was to fly a fully configured CAT ii autoland to a full stop on the long runway at ZZZ. During approach intermittent slat disag alerts triggered intermittent stick shaker and red speed boxes on the airspeed tape. Configuration changes were made mid-airspeed range for each new configuration in consideration of the possibility of an actual asymmetric deployment of the flight controls. Added 5 knots to approach speed as a safety margin; but flying qualities of the aircraft remained nominal throughout every configuration change and while stabilized on final. No uncommanded rolling moment was noted in any phase. Uneventful landing and taxi in. Suspected aircraft slat position sensor fault.

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Original NASA ASRS Text

Title: MD11 flight crew reported evaluating the landing options with a faulty LH #4 slat position sensor.

Narrative: While configuring for the approach on a dog-leg to intercept the localizer XXL at ZZZ; received level 2 SLAT DISAG after extending flaps to 28. The alert initially stayed on for probably a minute and then went away. No uncommanded rolling moment. Discontinued the approach and referenced the QRH. [Notified] Approach. Brought the jumpseater into the cockpit to assist and provide oversight. Called the dispatcher on SATCOM and requested a conference call with [Maintenance Control]. [Maintenance Control] said datalinked telemetry from the aircraft reported a single sensor had faulted to a value of zero. I discussed and investigated the potential of an actual asymmetric slat situation vs only a sensor problem. I was satisfied with the level and depth of the information provided by [Maintenance Control] that [Maintenance Control] believed it was only a sensor problem. I ran through a decision tree of following the QRH level 2 SLAT DISAG procedure. A #1 thrust reverser MEL precondition; wet runway and poor data in the QRH procedure for landing distance with an reverser inop led me to understand that a 0RET/28 landing would probably result in stopping near the last brick of the runway. ZZZ1 was our alternate but their long runway was under construction and the runways available there were shorter than ZZZ XXR. We didn't have enough fuel to go anywhere else. After a conference with the First Officer; and bringing the senior jumpseat pilot into the decision process; I decided that due to a lack of uncommanded rolling moment; the intermittent nature of the problem and the telemetry data from the aircraft; the best course of action was to fly a fully configured CAT II Autoland to a full stop on the long runway at ZZZ. During approach intermittent SLAT DISAG alerts triggered intermittent stick shaker and red speed boxes on the airspeed tape. Configuration changes were made mid-airspeed range for each new configuration in consideration of the possibility of an actual asymmetric deployment of the flight controls. Added 5 knots to approach speed as a safety margin; but flying qualities of the aircraft remained nominal throughout every configuration change and while stabilized on final. No uncommanded rolling moment was noted in any phase. Uneventful landing and taxi in. Suspected aircraft slat position sensor fault.

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.