Narrative:

Sea-lax. Just prior to descent phase at above listed position, aircraft encountered severe wake turbulence. Aircraft began to shake, then rolled rapidly to left to approximately 50-55 degree angle of bank. The nose dropped, autoplt had disconnected, and both pilots took manual control of aircraft. Wings were leveled with loss of 300 ft altitude. As captain, I contacted ZLA to inform them of our encounter and asked if there was any traffic ahead. They informed us that we were following a b- 747 into lax. I requested a heading deviation away from tract of the 747 and separation from the 747. I contacted the flight attendants to conduct a cabin check of the passenger. They reported no injuries. I explained to the passenger what happened and continued to lax for a normal landing. ZLA quality assurance personnel were called as well as management personnel to coordinate a follow-up evaluation of this incident. Callback conversation with reporter revealed the following: the B747 was descending and was 10 mi ahead of the reporter's md-80. The first indication of the wake was a slight 'rumble' in the MD80's airframe. Then the autoplt disconnected as the MD80 rolled 60 degrees to the left and lost 200-300 ft. Both the first officer (who was flying) and the reporter (captain) grabbed the controls and recovered the aircraft and climbed back to FL330. Only after they inquired did the ARTCC radar controller tell the crew about the B747. The reporter then requested to be vectored off-track for the rest of the leg to lax. This event occurred about 60 mi northwest of fim. The reporter suggests that the wake turbulence advisory program be expanded to include advisories during cruise as well as the traffic pattern and final approach. He said that the flight crew temporarily loss control of the aircraft and the flight attendants and passenger were badly frightened. One couple, who were scheduled to continue to mexico, instead took the train back to sea. The reporter further states that, at the time of the encounter, they were cruising at .78 mach and usually ZLA starts slowing everyone down around this area. If the aircraft had been at a much lower speed they would have stalled and lost a great amount of altitude during the recovery.

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Original NASA ASRS Text

Title: WAKE TURB -- IN CRUISE.

Narrative: SEA-LAX. JUST PRIOR TO DSCNT PHASE AT ABOVE LISTED POS, ACFT ENCOUNTERED SEVERE WAKE TURB. ACFT BEGAN TO SHAKE, THEN ROLLED RAPIDLY TO L TO APPROX 50-55 DEG ANGLE OF BANK. THE NOSE DROPPED, AUTOPLT HAD DISCONNECTED, AND BOTH PLTS TOOK MANUAL CTL OF ACFT. WINGS WERE LEVELED WITH LOSS OF 300 FT ALT. AS CAPT, I CONTACTED ZLA TO INFORM THEM OF OUR ENCOUNTER AND ASKED IF THERE WAS ANY TFC AHEAD. THEY INFORMED US THAT WE WERE FOLLOWING A B- 747 INTO LAX. I REQUESTED A HDG DEV AWAY FROM TRACT OF THE 747 AND SEPARATION FROM THE 747. I CONTACTED THE FLT ATTENDANTS TO CONDUCT A CABIN CHK OF THE PAX. THEY RPTED NO INJURIES. I EXPLAINED TO THE PAX WHAT HAPPENED AND CONTINUED TO LAX FOR A NORMAL LNDG. ZLA QUALITY ASSURANCE PERSONNEL WERE CALLED AS WELL AS MGMNT PERSONNEL TO COORDINATE A FOLLOW-UP EVALUATION OF THIS INCIDENT. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE B747 WAS DSNDING AND WAS 10 MI AHEAD OF THE RPTR'S MD-80. THE FIRST INDICATION OF THE WAKE WAS A SLIGHT 'RUMBLE' IN THE MD80'S AIRFRAME. THEN THE AUTOPLT DISCONNECTED AS THE MD80 ROLLED 60 DEGS TO THE L AND LOST 200-300 FT. BOTH THE FO (WHO WAS FLYING) AND THE RPTR (CAPT) GRABBED THE CTLS AND RECOVERED THE ACFT AND CLBED BACK TO FL330. ONLY AFTER THEY INQUIRED DID THE ARTCC RADAR CTLR TELL THE CREW ABOUT THE B747. THE RPTR THEN REQUESTED TO BE VECTORED OFF-TRACK FOR THE REST OF THE LEG TO LAX. THIS EVENT OCCURRED ABOUT 60 MI NW OF FIM. THE RPTR SUGGESTS THAT THE WAKE TURB ADVISORY PROGRAM BE EXPANDED TO INCLUDE ADVISORIES DURING CRUISE AS WELL AS THE TFC PATTERN AND FINAL APCH. HE SAID THAT THE FLC TEMPORARILY LOSS CTL OF THE ACFT AND THE FLT ATTENDANTS AND PAX WERE BADLY FRIGHTENED. ONE COUPLE, WHO WERE SCHEDULED TO CONTINUE TO MEXICO, INSTEAD TOOK THE TRAIN BACK TO SEA. THE RPTR FURTHER STATES THAT, AT THE TIME OF THE ENCOUNTER, THEY WERE CRUISING AT .78 MACH AND USUALLY ZLA STARTS SLOWING EVERYONE DOWN AROUND THIS AREA. IF THE ACFT HAD BEEN AT A MUCH LOWER SPD THEY WOULD HAVE STALLED AND LOST A GREAT AMOUNT OF ALT DURING THE RECOVERY.

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.