Aircraft icing. - NASA ASRS

Attributes
ACN	290058
Time
Date	199411
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 3000 msl bound upper : 4000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Navigation In Use	Other Other
Flight Phase	descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 250 flight time total : 6000 flight time type : 4000
ASRS Report	290058
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	inflight encounter : weather other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

While on approach to runway 27L at ord our aircraft executed an uncommanded roll excursion right to approximately 20 degrees of bank. There was no noticeable buffet throughout the whole approach. This was the only time 20 degrees of bank was executed. Prior to this roll the aileron controls were in the near neutral position. Simply put, from the time we encountered this phenomenon, the aircraft had an unusual or weird feel for a fraction of a second. This unusual feeling could be considered as uncontrollable. This unusual feeling was also recalled as strange by our flight attendant. The following facts apply to this incident: type aircraft -- ATR-42. Flaps 15 degrees in descent. IMC with ice accumulation, clear and rime. Speed 160-170 KIAS plus or minus 5 KTS. Turbulence light to moderate. On GS, on localizer. Altitude 4000-3000 ft. Weight 35000 pounds. Fuel 2300 pounds. Level 1, 2, 3, ice protection engaged. All FARS complied with.

Original NASA ASRS Text

Title: ACFT ICING.

Narrative: WHILE ON APCH TO RWY 27L AT ORD OUR ACFT EXECUTED AN UNCOMMANDED ROLL EXCURSION R TO APPROX 20 DEGS OF BANK. THERE WAS NO NOTICEABLE BUFFET THROUGHOUT THE WHOLE APCH. THIS WAS THE ONLY TIME 20 DEGS OF BANK WAS EXECUTED. PRIOR TO THIS ROLL THE AILERON CTLS WERE IN THE NEAR NEUTRAL POS. SIMPLY PUT, FROM THE TIME WE ENCOUNTERED THIS PHENOMENON, THE ACFT HAD AN UNUSUAL OR WEIRD FEEL FOR A FRACTION OF A SECOND. THIS UNUSUAL FEELING COULD BE CONSIDERED AS UNCTLABLE. THIS UNUSUAL FEELING WAS ALSO RECALLED AS STRANGE BY OUR FLT ATTENDANT. THE FOLLOWING FACTS APPLY TO THIS INCIDENT: TYPE ACFT -- ATR-42. FLAPS 15 DEGS IN DSCNT. IMC WITH ICE ACCUMULATION, CLR AND RIME. SPD 160-170 KIAS PLUS OR MINUS 5 KTS. TURB LIGHT TO MODERATE. ON GS, ON LOC. ALT 4000-3000 FT. WT 35000 LBS. FUEL 2300 LBS. LEVEL 1, 2, 3, ICE PROTECTION ENGAGED. ALL FARS COMPLIED WITH.

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.