A B737 encounters wake turbulence at 4000 ft when following 5 pt 5 mi behind a B757 on approach.

Attributes
ACN	554022
Time
Date	200207
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	intersection : adame
State Reference	IL
Altitude	msl single value : 4000
Environment
Flight Conditions	VMC
Weather Elements	other
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
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	B757 Undifferentiated or Other Model
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 : 200 flight time total : 16000 flight time type : 4245
ASRS Report	554022
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Experience	flight time last 90 days : 173
ASRS Report	554021
Events
Anomaly	altitude deviation : excursion from assigned altitude cabin event other inflight encounter : wake turbulence inflight encounter : turbulence
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took precautionary avoidance action other
Consequence	other other
Supplementary
Problem Areas	Environmental Factor
Primary Problem	Environmental Factor

Narrative:

On approach to runway 27L, following a B757, 5 1/2 mi ahead, encountered moderate wake turbulence. Aircraft rolled in excess of 30 degrees, first officer was PF. Disconnected autoplt, climbed about 200 ft to smooth air. Continued approach uneventfully. Upon arrival, found out 1 flight attendant had injured her hand in the encounter. No other injuries reported. Callback conversation with reporter revealed the following information: the reporter stated that he had noticed calls from preceding aircraft on the approach questioning the type aircraft they were following, which keyed him into the fact that the conditions were such that wakes were not dissipating. It was a very smooth flight condition otherwise with almost no wind. ATC was notified and speed was reduced to increase separation. The flight attendant injury was minor.

Original NASA ASRS Text

Title: A B737 ENCOUNTERS WAKE TURB AT 4000 FT WHEN FOLLOWING 5 PT 5 MI BEHIND A B757 ON APCH.

Narrative: ON APCH TO RWY 27L, FOLLOWING A B757, 5 1/2 MI AHEAD, ENCOUNTERED MODERATE WAKE TURB. ACFT ROLLED IN EXCESS OF 30 DEGS, FO WAS PF. DISCONNECTED AUTOPLT, CLBED ABOUT 200 FT TO SMOOTH AIR. CONTINUED APCH UNEVENTFULLY. UPON ARR, FOUND OUT 1 FLT ATTENDANT HAD INJURED HER HAND IN THE ENCOUNTER. NO OTHER INJURIES RPTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT HE HAD NOTICED CALLS FROM PRECEDING ACFT ON THE APCH QUESTIONING THE TYPE ACFT THEY WERE FOLLOWING, WHICH KEYED HIM INTO THE FACT THAT THE CONDITIONS WERE SUCH THAT WAKES WERE NOT DISSIPATING. IT WAS A VERY SMOOTH FLT CONDITION OTHERWISE WITH ALMOST NO WIND. ATC WAS NOTIFIED AND SPD WAS REDUCED TO INCREASE SEPARATION. THE FLT ATTENDANT INJURY WAS MINOR.

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.