A B737 reports severe wake turbulence 5 NM in trail of a B757 on sfo runway 28R. Full left and right aileron inputs required to maintain aircraft control.

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Attributes
ACN	778214
Time
Date	200803
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl single value : 4000
Environment
Flight Conditions	Marginal
Aircraft 1
Controlling Facilities	tracon : nct.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 28r
Route In Use	approach : instrument precision
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : nct.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
Experience	flight time last 90 days : 210 flight time total : 13000 flight time type : 9000
ASRS Report	778214
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	Weather Environmental Factor Airspace Structure Aircraft
Primary Problem	Environmental Factor

Narrative:

First officer was flying; we were on the ILS to runway 28R in sfo on GS 5 miles behind a B757. At approximately 4000 ft encountered severe wake turbulence requiring full left aileron and full left rudder to maintain a 30 degree right bank. This was followed by neutral controls then full right aileron and full right rudder to maintain 20 degree left bank. We gained control and offset to the right and remained high on GS for the remainder of approach. We got the runways in sight and then we were cleared to land runway 28L. On approach we had a 20 KT headwind and when we offset there was a wind shift to a right quartering headwind and then back to headwind.

Original NASA ASRS Text

Title: A B737 RPTS SEVERE WAKE TURB 5 NM IN TRAIL OF A B757 ON SFO RWY 28R. FULL L AND R AILERON INPUTS REQUIRED TO MAINTAIN ACFT CTL.

Narrative: FO WAS FLYING; WE WERE ON THE ILS TO RWY 28R IN SFO ON GS 5 MILES BEHIND A B757. AT APPROX 4000 FT ENCOUNTERED SEVERE WAKE TURBULENCE REQUIRING FULL L AILERON AND FULL L RUDDER TO MAINTAIN A 30 DEG R BANK. THIS WAS FOLLOWED BY NEUTRAL CTLS THEN FULL R AILERON AND FULL R RUDDER TO MAINTAIN 20 DEG L BANK. WE GAINED CTL AND OFFSET TO THE R AND REMAINED HIGH ON GS FOR THE REMAINDER OF APCH. WE GOT THE RWYS IN SIGHT AND THEN WE WERE CLRED TO LAND RWY 28L. ON APCH WE HAD A 20 KT HEADWIND AND WHEN WE OFFSET THERE WAS A WIND SHIFT TO A R QUARTERING HEADWIND AND THEN BACK TO HEADWIND.

Data retrieved from NASA's ASRS site as of May 2009 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.