Narrative:

En route to houston east of el paso we encountered moderate turbulence with a hard left roll that exceeded the capability of the autoplt. I immediately disconnected the autoplt and recovered to wings level attitude. During the recovery I initially lost about 200 ft of altitude in turbulence before reaching smooth air. We continued to lose an additional 300 ft before arresting the descent. Our total loss of altitude was 500 ft (FL385). During the process; the first officer advised ATC of the turbulence and at that time they noticed the descent and told us to maintain FL390. I told the first officer that I was unable to maintain altitude and to ask for an immediate lower altitude. After about 30 seconds; I was able to recover about 200 ft of altitude before abq cleared us to FL370. The remainder of the flight was uneventful. During the preceding moments of the flight; I noticed an airplane that was climbing off of our left side. He leveled at FL370; he was faster than we were and when he was about 12 miles ahead of us; he was issued FL390. Our courses converged east of el paso and that was where the upset occurred. After the event I asked the controller what type of airplane he had climbed in front of us; he reluctantly admitted that it was another carrier B777. The only action that could have prevented this event would be for the controller who issued the climb to have considered the effect wake turbulence has (especially heavy widebody airplanes) on other aircraft and allow sufficient room between them. As pilots; we all understand that the effects of wake turbulence can be felt for 30 miles or more behind heavy aircraft. You would think that controllers would have access to the same information!

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Original NASA ASRS Text

Title: B737-700 ENCOUNTERED WAKE TURB AT CRUISE ALT. ACFT ROLLED AND LOST 500 FT BEFORE DSCNT WAS ARRESTED.

Narrative: ENRTE TO HOUSTON EAST OF EL PASO WE ENCOUNTERED MODERATE TURBULENCE WITH A HARD L ROLL THAT EXCEEDED THE CAPABILITY OF THE AUTOPLT. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND RECOVERED TO WINGS LEVEL ATTITUDE. DURING THE RECOVERY I INITIALLY LOST ABOUT 200 FT OF ALTITUDE IN TURBULENCE BEFORE REACHING SMOOTH AIR. WE CONTINUED TO LOSE AN ADDITIONAL 300 FT BEFORE ARRESTING THE DSCNT. OUR TOTAL LOSS OF ALTITUDE WAS 500 FT (FL385). DURING THE PROCESS; THE FO ADVISED ATC OF THE TURBULENCE AND AT THAT TIME THEY NOTICED THE DSCNT AND TOLD US TO MAINTAIN FL390. I TOLD THE FO THAT I WAS UNABLE TO MAINTAIN ALTITUDE AND TO ASK FOR AN IMMEDIATE LOWER ALTITUDE. AFTER ABOUT 30 SECONDS; I WAS ABLE TO RECOVER ABOUT 200 FT OF ALTITUDE BEFORE ABQ CLRED US TO FL370. THE REMAINDER OF THE FLT WAS UNEVENTFUL. DURING THE PRECEDING MOMENTS OF THE FLT; I NOTICED AN AIRPLANE THAT WAS CLBING OFF OF OUR L SIDE. HE LEVELED AT FL370; HE WAS FASTER THAN WE WERE AND WHEN HE WAS ABOUT 12 MILES AHEAD OF US; HE WAS ISSUED FL390. OUR COURSES CONVERGED E OF EL PASO AND THAT WAS WHERE THE UPSET OCCURRED. AFTER THE EVENT I ASKED THE CTLR WHAT TYPE OF AIRPLANE HE HAD CLBED IN FRONT OF US; HE RELUCTANTLY ADMITTED THAT IT WAS ANOTHER CARRIER B777. THE ONLY ACTION THAT COULD HAVE PREVENTED THIS EVENT WOULD BE FOR THE CTLR WHO ISSUED THE CLB TO HAVE CONSIDERED THE EFFECT WAKE TURBULENCE HAS (ESPECIALLY HEAVY WIDEBODY AIRPLANES) ON OTHER ACFT AND ALLOW SUFFICIENT ROOM BETWEEN THEM. AS PLTS; WE ALL UNDERSTAND THAT THE EFFECTS OF WAKE TURBULENCE CAN BE FELT FOR 30 MILES OR MORE BEHIND HEAVY ACFT. YOU WOULD THINK THAT CTLRS WOULD HAVE ACCESS TO THE SAME INFO!

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.