A B737-500 descending in bay TRACON airspace encounters wake turbulence from another B737 7 mi ahead. Flight crew is surprised how much their aircraft rolls this distance from leading aircraft. Flight crew wants advisory of type of any aircraft in front of them.

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Attributes
ACN	376432
Time
Date	199708
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : oak airport : sfo
State Reference	CA
Altitude	msl bound lower : 7000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : oak
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival star : star
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 3000
ASRS Report	376432
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	inflight encounter other
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

Encountered wake turbulence 7 mi in trail of B737. Rolled 20-30 degrees. First officer used approximately 50% aileron to recover. Calm, clear day -- very little wind aloft. Callback conversation with reporter revealed the following information: reporter participated in the wake turbulence callback study. Reporter was surprised at the strength of the wake from a preceding B737 7 mi ahead on the same arrival. Reporter feels spacing and type of aircraft being followed should be issued at all times to alert a following aircraft as to the possibility of wake turbulence. Aircraft roll was sharp and up to 30 degrees, but not much other effect.

Original NASA ASRS Text

Title: A B737-500 DSNDING IN BAY TRACON AIRSPACE ENCOUNTERS WAKE TURB FROM ANOTHER B737 7 MI AHEAD. FLC IS SURPRISED HOW MUCH THEIR ACFT ROLLS THIS DISTANCE FROM LEADING ACFT. FLC WANTS ADVISORY OF TYPE OF ANY ACFT IN FRONT OF THEM.

Narrative: ENCOUNTERED WAKE TURB 7 MI IN TRAIL OF B737. ROLLED 20-30 DEGS. FO USED APPROX 50% AILERON TO RECOVER. CALM, CLR DAY -- VERY LITTLE WIND ALOFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN THE WAKE TURB CALLBACK STUDY. RPTR WAS SURPRISED AT THE STRENGTH OF THE WAKE FROM A PRECEDING B737 7 MI AHEAD ON THE SAME ARR. RPTR FEELS SPACING AND TYPE OF ACFT BEING FOLLOWED SHOULD BE ISSUED AT ALL TIMES TO ALERT A FOLLOWING ACFT AS TO THE POSSIBILITY OF WAKE TURB. ACFT ROLL WAS SHARP AND UP TO 30 DEGS, BUT NOT MUCH OTHER EFFECT.

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.