A B747-400 captain reports wake turbulence at about 800 ft behind a B777 on takeoff at vhhh.

Attributes
ACN	812623
Time
Date	200811
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : vhhh.airport
State Reference	FO
Altitude	agl single value : 800
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 129
Flight Phase	climbout : initial
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 : 16000 flight time type : 2500
ASRS Report	812623
Events
Anomaly	inflight encounter : wake turbulence non adherence : published procedure other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control
Supplementary
Problem Areas	ATC Human Performance Airport
Primary Problem	ATC Human Performance

Narrative:

We were cleared to takeoff on runway 7R behind a B777. I was concerned about the possibility of wake turbulence since we were only about 4.8 NM behind the preceding heavy. At about 800 ft; we encountered wake turbulence which lasted about 20 seconds. This is the 3RD wake turbulence encounter that I have encountered while on approach or taking off from vhhh in recent weeks.

Original NASA ASRS Text

Title: A B747-400 CAPT RPTS WAKE TURBULENCE AT ABOUT 800 FT BEHIND A B777 ON TKOF AT VHHH.

Narrative: WE WERE CLRED TO TKOF ON RWY 7R BEHIND A B777. I WAS CONCERNED ABOUT THE POSSIBILITY OF WAKE TURBULENCE SINCE WE WERE ONLY ABOUT 4.8 NM BEHIND THE PRECEDING HEAVY. AT ABOUT 800 FT; WE ENCOUNTERED WAKE TURBULENCE WHICH LASTED ABOUT 20 SECONDS. THIS IS THE 3RD WAKE TURBULENCE ENCOUNTER THAT I HAVE ENCOUNTERED WHILE ON APCH OR TAKING OFF FROM VHHH IN RECENT WEEKS.

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.