A fokker 100 experienced wing anti-ice failure during descent into mdw and diverted into ord.

Attributes
ACN	434589
Time
Date	199904
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	msl single value : 10000
Environment
Flight Conditions	IMC
Weather Elements	Ice Rain
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	434589
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : multi engine pilot : instrument
ASRS Report	434590
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : diverted to alternate
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Descending through FL220 for mdw, encountered icing conditions. Switched on all anti-icing. At 10000 ft, approximately 25 NM south of mdw, wing anti-ice faulted with MFDU procedure displayed and fault in switch. Reset wing anti-icing and fault, again. Still in icing conditions with little change expected to touchdown. ATIS information 360 degrees at 9 KTS, 10 SM, -RA 24, scattered 42, overcast 7/2, altimeter 29.44. Runway wet. Abnormal called for flaps 25 degrees +20 KIAS additive. Elected to divert into ord. Approach was apprised of situation and diversion necessity. Ord approach immediately issued a 320 degree heading to intercept runway 4R ord, and offered any assistance we would need. An uneventful landing followed at ord runway 4R. What I realized after landing and speaking with dispatch was that ord was not an alternate. This action on my part may therefore constitute exercise of emergency authority/authorized. Supplemental information from acn 434590: checklist procedures accomplished required flaps 25 degrees and vref +20 KTS.

Original NASA ASRS Text

Title: A FOKKER 100 EXPERIENCED WING ANTI-ICE FAILURE DURING DSCNT INTO MDW AND DIVERTED INTO ORD.

Narrative: DSNDING THROUGH FL220 FOR MDW, ENCOUNTERED ICING CONDITIONS. SWITCHED ON ALL ANTI-ICING. AT 10000 FT, APPROX 25 NM S OF MDW, WING ANTI-ICE FAULTED WITH MFDU PROC DISPLAYED AND FAULT IN SWITCH. RESET WING ANTI-ICING AND FAULT, AGAIN. STILL IN ICING CONDITIONS WITH LITTLE CHANGE EXPECTED TO TOUCHDOWN. ATIS INFO 360 DEGS AT 9 KTS, 10 SM, -RA 24, SCATTERED 42, OVCST 7/2, ALTIMETER 29.44. RWY WET. ABNORMAL CALLED FOR FLAPS 25 DEGS +20 KIAS ADDITIVE. ELECTED TO DIVERT INTO ORD. APCH WAS APPRISED OF SIT AND DIVERSION NECESSITY. ORD APCH IMMEDIATELY ISSUED A 320 DEG HDG TO INTERCEPT RWY 4R ORD, AND OFFERED ANY ASSISTANCE WE WOULD NEED. AN UNEVENTFUL LNDG FOLLOWED AT ORD RWY 4R. WHAT I REALIZED AFTER LNDG AND SPEAKING WITH DISPATCH WAS THAT ORD WAS NOT AN ALTERNATE. THIS ACTION ON MY PART MAY THEREFORE CONSTITUTE EXERCISE OF EMER AUTH. SUPPLEMENTAL INFO FROM ACN 434590: CHKLIST PROCS ACCOMPLISHED REQUIRED FLAPS 25 DEGS AND VREF +20 KTS.

Data retrieved from NASA's ASRS site as of July 2007 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.