A B737-300 encountered wake turbulence following a B757 on descent into sea on the chins arrival.

Attributes
ACN	706631
Time
Date	200608
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sea.airport
State Reference	WA
Altitude	msl single value : 24000
Aircraft 1
Controlling Facilities	artcc : zse.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : vacating altitude
Route In Use	departure : noise abatement departure sid : chins
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zse.artcc
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 240 flight time total : 12000 flight time type : 5400
ASRS Report	706631
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	inflight encounter : wake turbulence other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Supplementary
Problem Areas	Environmental Factor
Primary Problem	Environmental Factor

Narrative:

Descending to FL240 on the chins arrival to sea; we encountered wake turbulence off of a B757 descending ahead of us. Aircraft banked to 15 degrees before the autoplt could be disengaged; recovery was uneventful. No injuries reported despite the abruptness of the turbulence encounter. We were not aware of the B757 until after the incident. The B757 was 12 mi ahead of us but had descended through our altitude a few mins prior. Remainder of the flight was without incident.

Original NASA ASRS Text

Title: A B737-300 ENCOUNTERED WAKE TURB FOLLOWING A B757 ON DSCNT INTO SEA ON THE CHINS ARR.

Narrative: DSNDING TO FL240 ON THE CHINS ARR TO SEA; WE ENCOUNTERED WAKE TURB OFF OF A B757 DSNDING AHEAD OF US. ACFT BANKED TO 15 DEGS BEFORE THE AUTOPLT COULD BE DISENGAGED; RECOVERY WAS UNEVENTFUL. NO INJURIES RPTED DESPITE THE ABRUPTNESS OF THE TURB ENCOUNTER. WE WERE NOT AWARE OF THE B757 UNTIL AFTER THE INCIDENT. THE B757 WAS 12 MI AHEAD OF US BUT HAD DSNDED THROUGH OUR ALT A FEW MINS PRIOR. REMAINDER OF THE FLT WAS WITHOUT INCIDENT.

Data retrieved from NASA's ASRS site as of January 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.