Wake turbulence encounter.

Attributes
ACN	299779
Time
Date	199503
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : smo airport : lax
State Reference	CA
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach landing other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 15000 flight time type : 900
ASRS Report	299779
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	inflight encounter other other anomaly other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	other

Narrative:

While being vectored in-trail for lax, an air carrier 747-400 was vectored over top of us and descended in front. Spacing was never less than 8 mi. We received buffet and roll from previous aircraft that was strong enough at one point to induce 45 degree bank and disconnect autoplt. Corrective action: requested slower speed and more spacing behind aircraft. ATC repeatedly stated that preceding aircraft was 8 mi ahead. Contributing factors: newer wing designs produce wake that is potentially hazardous to larger aircraft and in- trail spacing behind these newer aircraft needs to be reevaluated. Callback conversation with reporter revealed the following information: as reporter and flight crew were descending through 8000 ft they encountered wake turbulence from a preceding B-747-400 that was 8 mi ahead of them. The turbulence was strong enough to roll the aircraft into a 45 degree bank. Reporter's aircraft was being flown by autoplt which disengaged as the aircraft approached 45 degrees of bank angle. Flight path displacement was 200 ft. Event was disturbing to flight crew and passenger. After the 5 second event the aircraft was righted and continued uneventfully for a landing. Preceding aircraft was always announced as 8 mi ahead. This distance was verified by TCASII.

Original NASA ASRS Text

Title: WAKE TURB ENCOUNTER.

Narrative: WHILE BEING VECTORED IN-TRAIL FOR LAX, AN ACR 747-400 WAS VECTORED OVER TOP OF US AND DSNDED IN FRONT. SPACING WAS NEVER LESS THAN 8 MI. WE RECEIVED BUFFET AND ROLL FROM PREVIOUS ACFT THAT WAS STRONG ENOUGH AT ONE POINT TO INDUCE 45 DEG BANK AND DISCONNECT AUTOPLT. CORRECTIVE ACTION: REQUESTED SLOWER SPD AND MORE SPACING BEHIND ACFT. ATC REPEATEDLY STATED THAT PRECEDING ACFT WAS 8 MI AHEAD. CONTRIBUTING FACTORS: NEWER WING DESIGNS PRODUCE WAKE THAT IS POTENTIALLY HAZARDOUS TO LARGER ACFT AND IN- TRAIL SPACING BEHIND THESE NEWER ACFT NEEDS TO BE REEVALUATED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AS RPTR AND FLC WERE DSNDING THROUGH 8000 FT THEY ENCOUNTERED WAKE TURB FROM A PRECEDING B-747-400 THAT WAS 8 MI AHEAD OF THEM. THE TURB WAS STRONG ENOUGH TO ROLL THE ACFT INTO A 45 DEG BANK. RPTR'S ACFT WAS BEING FLOWN BY AUTOPLT WHICH DISENGAGED AS THE ACFT APCHED 45 DEGS OF BANK ANGLE. FLT PATH DISPLACEMENT WAS 200 FT. EVENT WAS DISTURBING TO FLC AND PAX. AFTER THE 5 SECOND EVENT THE ACFT WAS RIGHTED AND CONTINUED UNEVENTFULLY FOR A LNDG. PRECEDING ACFT WAS ALWAYS ANNOUNCED AS 8 MI AHEAD. THIS DISTANCE WAS VERIFIED BY TCASII.

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.