Narrative:

Level at FL240 we encountered the wake turbulence of a B747. Aircraft was buffeted strongly, strong jolts were felt and the aircraft rolled to the right, I believe beyond 60 degrees. During the recovery maneuver, further rolls both left and right of equal and lesser magnitude were experienced. Neither the captain nor myself were aware of our proximity to or the status of the B747. We had been on several delay vectors for spacing on the arrival route. We were proceeding direct to the VOR (fim VOR) and were within approximately 10 mi when the event took place. Both crew members were conducting an approach briefing at the time. My TCASII was set to 'abv' and the captain's was 'norm.' numerous vectors immediately prior to the event contributed to poor situational awareness with regard to traffic. ATC failed to advise that we were following a heavy. Incident reinforces the need to utilize TCASII in all phases of flight not only for collision avoidance but also for spacing, aircraft identify and turbulence avoidance. I attribute my company's excellent training in upset recovery to minimizing the injuries from this incident. Callback conversation with reporter revealed the following information: the reporter was the first officer on an air carrier B737-300 that, unknown to them at the time, was behind a B747. All of the aircraft were being vectored as they approached fim, for spacing, and he thinks that both the flight crew and the controller lost situational awareness regarding the possibility of wake turbulence. The initial indication, according to the reporter, was an increasingly violent buffeting then a strong, pronounced rolling movement. He said that there was no pitch change or yaw, but a slight weightlessness. At first, the autoplt appeared to be successfully countering the wake activity, but the roll kept increasing and the altitude loss began so the reporter disconnected the autoplt and started his corrective actions. As he reached full travel on the ailerons he noticed that the captain was also on the controls. He said that the whole event lasted from 10-30 seconds of time. Later, there were several minor wake events from the same aircraft. One of the cabin attendants was injured when a suitcase spilled out of an overhead bin and struck her on the head. She was taken to a hospital for treatment. The controller expressed surprise that the flight crew did not know of the B747 beforehand. The flight crew normally watches for other traffic by observing their TCASII display as well as by looking out of the window, the reporter said. But, this time the TCASII did not show the B747 freighter for some reason. He said that the controller apologized for not warning about the possibility of wake turbulence. The B747 was approximately 10-15 NM ahead of them the reporter said.

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Original NASA ASRS Text

Title: THE ACR FLC OF A B737-300 HITS THE WAKE OF A B747 AT FL240 AND ROLLS AND DSNDS WHILE ATTEMPTING TO COUNTER THE WAKE EFFECT AND A CABIN ATTENDANT IS INJURED. PRIOR TO THE ENCOUNTER, THERE WAS NO WARNING OF A WAKE POSSIBILITY.

Narrative: LEVEL AT FL240 WE ENCOUNTERED THE WAKE TURB OF A B747. ACFT WAS BUFFETED STRONGLY, STRONG JOLTS WERE FELT AND THE ACFT ROLLED TO THE R, I BELIEVE BEYOND 60 DEGS. DURING THE RECOVERY MANEUVER, FURTHER ROLLS BOTH L AND R OF EQUAL AND LESSER MAGNITUDE WERE EXPERIENCED. NEITHER THE CAPT NOR MYSELF WERE AWARE OF OUR PROX TO OR THE STATUS OF THE B747. WE HAD BEEN ON SEVERAL DELAY VECTORS FOR SPACING ON THE ARR RTE. WE WERE PROCEEDING DIRECT TO THE VOR (FIM VOR) AND WERE WITHIN APPROX 10 MI WHEN THE EVENT TOOK PLACE. BOTH CREW MEMBERS WERE CONDUCTING AN APCH BRIEFING AT THE TIME. MY TCASII WAS SET TO 'ABV' AND THE CAPT'S WAS 'NORM.' NUMEROUS VECTORS IMMEDIATELY PRIOR TO THE EVENT CONTRIBUTED TO POOR SITUATIONAL AWARENESS WITH REGARD TO TFC. ATC FAILED TO ADVISE THAT WE WERE FOLLOWING A HVY. INCIDENT REINFORCES THE NEED TO UTILIZE TCASII IN ALL PHASES OF FLT NOT ONLY FOR COLLISION AVOIDANCE BUT ALSO FOR SPACING, ACFT IDENT AND TURB AVOIDANCE. I ATTRIBUTE MY COMPANY'S EXCELLENT TRAINING IN UPSET RECOVERY TO MINIMIZING THE INJURIES FROM THIS INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE FO ON AN ACR B737-300 THAT, UNKNOWN TO THEM AT THE TIME, WAS BEHIND A B747. ALL OF THE ACFT WERE BEING VECTORED AS THEY APCHED FIM, FOR SPACING, AND HE THINKS THAT BOTH THE FLC AND THE CTLR LOST SITUATIONAL AWARENESS REGARDING THE POSSIBILITY OF WAKE TURB. THE INITIAL INDICATION, ACCORDING TO THE RPTR, WAS AN INCREASINGLY VIOLENT BUFFETING THEN A STRONG, PRONOUNCED ROLLING MOVEMENT. HE SAID THAT THERE WAS NO PITCH CHANGE OR YAW, BUT A SLIGHT WEIGHTLESSNESS. AT FIRST, THE AUTOPLT APPEARED TO BE SUCCESSFULLY COUNTERING THE WAKE ACTIVITY, BUT THE ROLL KEPT INCREASING AND THE ALT LOSS BEGAN SO THE RPTR DISCONNECTED THE AUTOPLT AND STARTED HIS CORRECTIVE ACTIONS. AS HE REACHED FULL TRAVEL ON THE AILERONS HE NOTICED THAT THE CAPT WAS ALSO ON THE CTLS. HE SAID THAT THE WHOLE EVENT LASTED FROM 10-30 SECONDS OF TIME. LATER, THERE WERE SEVERAL MINOR WAKE EVENTS FROM THE SAME ACFT. ONE OF THE CABIN ATTENDANTS WAS INJURED WHEN A SUITCASE SPILLED OUT OF AN OVERHEAD BIN AND STRUCK HER ON THE HEAD. SHE WAS TAKEN TO A HOSPITAL FOR TREATMENT. THE CTLR EXPRESSED SURPRISE THAT THE FLC DID NOT KNOW OF THE B747 BEFOREHAND. THE FLC NORMALLY WATCHES FOR OTHER TFC BY OBSERVING THEIR TCASII DISPLAY AS WELL AS BY LOOKING OUT OF THE WINDOW, THE RPTR SAID. BUT, THIS TIME THE TCASII DID NOT SHOW THE B747 FREIGHTER FOR SOME REASON. HE SAID THAT THE CTLR APOLOGIZED FOR NOT WARNING ABOUT THE POSSIBILITY OF WAKE TURB. THE B747 WAS APPROX 10-15 NM AHEAD OF THEM THE RPTR SAID.

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.