Narrative:

We were in descent from 10;000 to 5;000 ft and had just switched to final approach; slowing to 230 KIAS. The weather at our destination was 1.5 miles visibility in rain and mist. At some point in the arrival sequence the captain disconnected the autopilot and autothrottles in preparation for the approach. At that point I noted an IAS miscompare warning on the pfd; followed by level 2 alerts: 'sel elev feel man; sel flap lim ovrd'. I then noted pfd asi indications - captain's 217 KIAS; first officer's 236 KIAS; standby 235 KIAS.we ran the QRH airspeed lost; suspect; erratic checklist [and determined] CADC #1 was suspect. The captain selected CADC 2 for flight director; autpoilot; etc. No emergency was declared and we landed uneventfully. I missed the recommendation at beginning of QRH procedure [regarding] getting to and maintaining VMC; as I was focused on getting the disparity between the 2 asi displays resolved.we wrote the event up after the flight. This was a repeat of the same item which was signed off prior to our flight as replaced CADC #1. Maintenance action following our flight was signed off as 'purged moisture from #1 pitot static system'...I have no recommendation for prevention. The QRH checklist should; however; be amended to direct use of aoa when experiencing airspeed lost/suspect/erratic events. Anecdotal to this event was my familiarity [with the QRH procedure]; in part; due to recent completion of annual training where the pitot covered scenario directs its use.

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Original NASA ASRS Text

Title: An MD-11 flight crew successfully resolved anomalous airspeed indications during an arrival in IMC.

Narrative: We were in descent from 10;000 to 5;000 FT and had just switched to final approach; slowing to 230 KIAS. The weather at our destination was 1.5 miles visibility in rain and mist. At some point in the arrival sequence the Captain disconnected the autopilot and autothrottles in preparation for the approach. At that point I noted an IAS miscompare warning on the PFD; followed by Level 2 Alerts: 'SEL ELEV FEEL MAN; SEL FLAP LIM OVRD'. I then noted PFD ASI indications - Captain's 217 KIAS; First Officer's 236 KIAS; Standby 235 KIAS.We ran the QRH Airspeed Lost; Suspect; Erratic Checklist [and determined] CADC #1 was suspect. The Captain selected CADC 2 for Flight Director; autpoilot; etc. No emergency was declared and we landed uneventfully. I missed the recommendation at beginning of QRH procedure [regarding] getting to and maintaining VMC; as I was focused on getting the disparity between the 2 ASI displays resolved.We wrote the event up after the flight. This was a repeat of the same item which was signed off prior to our flight as replaced CADC #1. Maintenance action following our flight was signed off as 'Purged moisture from #1 Pitot Static System'...I have no recommendation for prevention. The QRH Checklist should; however; be amended to direct use of AOA when experiencing Airspeed Lost/Suspect/Erratic events. Anecdotal to this event was my familiarity [with the QRH procedure]; in part; due to recent completion of annual training where the pitot covered scenario directs its use.

Data retrieved from NASA's ASRS site as of July 2013 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.