MD-11 flight crew reported a Level 2 SLAT DISAG Caution Message reoccurring during approach. The flight crew continued to destination airport and landed.
Synopsis
MD-11 flight crew reported a Level 2 SLAT DISAG Caution Message reoccurring during approach. The flight crew continued to destination airport and landed.
Narrative
On arrival to ZZZ; told to slow to 210 kts. or lower. Initially configured to Slats extend and then Flaps 15 at 210 kts.. Slowed to 185 kts. and was descending to 3;000 feet MSL. Then (with no configuration change) had Level 2 SLAT DISAG Caution with increase to foot airspeed. After about 3-5 seconds; Caution went away for about 10 seconds. Caution returned and went away several times. Discontinued approach; [requested priority handling] and requested vectors. Accelerated to 220 kts.; requested climb to 5;000 feet MSL to reach VMC while working checklists. Caution never came back above 190 kts.. Contacted Dispatcher via Sat Phone. Checklist initially seemed to recommend a FLAPS 28/NO SLAT landing. Went through checklist again and decided to try to configure and see if caution returned. Slowed to 210 kts. (10 below flap 28 speed) and selected FLAPS 28. Slowed in 10 knot increments until 180 kts.. Selected gear down; then flaps 35 at 180 kts. Slowed to FMS speed before glide slope intercept. Caution never returned and landed normally.Event was caused by equipment malfunction.Event could have gone smoother if checklist was more clear. Initially; it seemed to direct a FLAP 28/NO SLAT landing. On a snowy Runway with moderate braking action; I am not sure we would have had successful landing with the high approach speeds associated with a no-slat landing.
Second reporter narrative
Shortly before intercepting the localizer for Runway XXR; Slats extended; Flaps 15; speed 200 kts. reducing to 180 kts.; Level 2 alert SLAT DISAG appeared on display; Amber Airspeed Foot coming up and aircraft pitch change to higher. The alert extinguished after a few seconds followed by several more SLAT DISAG alerts. We discontinued the approach; asked ATC for hold; [requested priority handling]; and contacted Dispatcher via Sat Phone. The alert disappeared while we were being vectored and aircraft pitch attitude appeared normal for the conditions; Flaps 15/EXT; speed 220 kts. The Captain elected not to do the SLAT DISAG checklist since the alert has extinguished and decided to do a normal Flaps 35/EXT landing. We requested a long final for the second approach; configured early; and no alerts appeared on display. The rest of the approach and landing was uneventful. Flight control system malfunction.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.