Flight crew of B737-500 encounter severe wake turbulence on arrival to ord, runway 22R.

Attributes
ACN	609545
Time
Date	200403
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 5000
Environment
Flight Conditions	Marginal
Aircraft 1
Controlling Facilities	tracon : c90.tracon tower : rhv.tower
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 251 flight time total : 17000 flight time type : 1200
ASRS Report	609545
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	inflight encounter : wake turbulence other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : exited adverse environment
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft Airport Environmental Factor
Primary Problem	Environmental Factor

Narrative:

We crossed the field at 9000 ft for a right downwind to runway 22R. We were vectored to intercept the runway 22R localizer at 5000 ft just inside of fnuch intersection. There was another aircraft 3 DME ahead of us -- also level at 5000 ft. I do not know what type. The wind read 210 degrees at 43 KTS. Just as we rolled level on the localizer, we encountered the wake turbulence of the aircraft ahead of us. The first effect was a roll of about 30 degrees bank followed by pitch oscillations. At one point the controls felt next to useless. I then put the nose down and the gear down and told the PNF to set 4000 ft level change, flaps 15 degrees, speed 150 KTS, call the tower and advise of our deviations. He did all of this and at about 4500 ft we were clear of the turbulence. With 4 mi separation after our speed change we had no future encounters with preceding airplane's wake. This situation was very difficult to control and it must have been very uncomfortable for the passenger. As a side note, this was the end of my 6TH consecutive day of duty at the end of a month.

Original NASA ASRS Text

Title: FLT CREW OF B737-500 ENCOUNTER SEVERE WAKE TURB ON ARR TO ORD, RWY 22R.

Narrative: WE CROSSED THE FIELD AT 9000 FT FOR A R DOWNWIND TO RWY 22R. WE WERE VECTORED TO INTERCEPT THE RWY 22R LOC AT 5000 FT JUST INSIDE OF FNUCH INTXN. THERE WAS ANOTHER ACFT 3 DME AHEAD OF US -- ALSO LEVEL AT 5000 FT. I DO NOT KNOW WHAT TYPE. THE WIND READ 210 DEGS AT 43 KTS. JUST AS WE ROLLED LEVEL ON THE LOC, WE ENCOUNTERED THE WAKE TURB OF THE ACFT AHEAD OF US. THE FIRST EFFECT WAS A ROLL OF ABOUT 30 DEGS BANK FOLLOWED BY PITCH OSCILLATIONS. AT ONE POINT THE CTLS FELT NEXT TO USELESS. I THEN PUT THE NOSE DOWN AND THE GEAR DOWN AND TOLD THE PNF TO SET 4000 FT LEVEL CHANGE, FLAPS 15 DEGS, SPD 150 KTS, CALL THE TWR AND ADVISE OF OUR DEVS. HE DID ALL OF THIS AND AT ABOUT 4500 FT WE WERE CLR OF THE TURB. WITH 4 MI SEPARATION AFTER OUR SPD CHANGE WE HAD NO FUTURE ENCOUNTERS WITH PRECEDING AIRPLANE'S WAKE. THIS SIT WAS VERY DIFFICULT TO CTL AND IT MUST HAVE BEEN VERY UNCOMFORTABLE FOR THE PAX. AS A SIDE NOTE, THIS WAS THE END OF MY 6TH CONSECUTIVE DAY OF DUTY AT THE END OF A MONTH.

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.