Sea B737 departure encounters wake of previous B747 departure.

Attributes
ACN	574722
Time
Date	200302
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sea.airport
State Reference	WA
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sea.tower
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	ground : takeoff roll
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : sea.tower
Operator	common carrier : air carrier
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time total : 1100
ASRS Report	574722
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	inflight encounter : turbulence inflight encounter : wake turbulence non adherence : required legal separation
Independent Detector	other other : 1
Resolutory Action	none taken : anomaly accepted
Supplementary
Problem Areas	Environmental Factor ATC Human Performance
Primary Problem	Ambiguous

Narrative:

Aircraft #2 took off directly ahead of aircraft #1 on runway 34R. Winds were light. Adequate separation was not maintained. Shortly after liftoff, aircraft #1 rolled rapidly and violently left to 35 degrees wing down. The roll occurred in 1 second or less. As quickly as the wake turbulence was entered it was exited, and the pilot recovered and continued a normal flight. The passenger were alarmed.

Original NASA ASRS Text

Title: SEA B737 DEP ENCOUNTERS WAKE OF PREVIOUS B747 DEP.

Narrative: ACFT #2 TOOK OFF DIRECTLY AHEAD OF ACFT #1 ON RWY 34R. WINDS WERE LIGHT. ADEQUATE SEPARATION WAS NOT MAINTAINED. SHORTLY AFTER LIFTOFF, ACFT #1 ROLLED RAPIDLY AND VIOLENTLY L TO 35 DEGS WING DOWN. THE ROLL OCCURRED IN 1 SECOND OR LESS. AS QUICKLY AS THE WAKE TURB WAS ENTERED IT WAS EXITED, AND THE PLT RECOVERED AND CONTINUED A NORMAL FLT. THE PAX WERE ALARMED.

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.