Narrative:

It was a beautiful day to fly. Our trip from sna-oak was the last of a 2 leg trip that day (first from ege-sna). We launched right on time from sna and quickly climbed to FL310. Flight plan: CHANL1 departure, gmn transition PXN2 arrival oak. We are used to competing on the airway space with air carrier's. Several aircraft reported turbulence at FL280, and the air carrier Y in front of us was one of them. As such, he requested and was granted a slower than normal speed of mach .72. Our cruise speed today was mach .80. Another air carrier Z behind us complained of bumps at lower altitudes and I volunteered that the ride at FL310 was fine, so ATC climbed the traffic behind us to FL310 as well. As we passed gmn, I could see the slower, lower air carrier Y jet in front of us. There was almost no wind this day, the FMS reported 6 KTS. The TCASII unit showed us gaining on him quite quickly. I knew this would be a conflict as we would both be descending for oak and I wasn't quite sure how ATC was planning on sorting out the descent. As it turned out, about 50 NM on pxn, ATC saw the problem and slowed us down to mach .75, asked the jet to speed up to 'maximum forward' and waited. Air carrier Y crept from 2 NM in front of us to 5 NM. Then we were both issued dscnts to make STAR crossing restrs (bored intersection at 10000 ft, 250 KTS). The jet started down, and so did we. At FL260, we found his wake: with the autoplt engaged, the airplane suddenly rolled 15 degrees right. I disconnected the autoplt, countered the roll and climbed slightly (400 ft), thinking we were in his wake and could climb above it. Out of 200 ft, the rolling and bucking trend instantly stopped. My first officer responded on the radio that we had climbed due to wake encounter and we continued down at a slower rate. I would estimate air carrier Y jet was 6-8 NM in front of us at this point. After crossing pxn VOR, we continued down and encountered it again at FL180. This time, I offset slightly to the right off course to avoid any further encounter. As we switched to norcal approach, ATC queried, 'I don't know how you are navigating, but you seem to be about 1 mi east of centerline.' I responded that we were exactly 1 NM east of centerline (per programming) due to wake turbulence with the jet preceding us into oak. There was silence, then ATC asked, 'not in my sector was it?' no, it was with center, prior to his handing us off to you. We were vectored onto final for runway 27R, while air carrier Y jet went to runway 29 and no further incidents were encountered or mentioned. Lessons: watch out in smooth air for relatively stable vortex generation and try to maintain 10 NM in-trail, versus 5 NM offered by ATC, even in a 50000 pound airplane!

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Original NASA ASRS Text

Title: G1 ARR INTO OAK EXPERIENCED A WAKE ENCOUNTER FROM PRECEDING B737 AT FL260.

Narrative: IT WAS A BEAUTIFUL DAY TO FLY. OUR TRIP FROM SNA-OAK WAS THE LAST OF A 2 LEG TRIP THAT DAY (FIRST FROM EGE-SNA). WE LAUNCHED RIGHT ON TIME FROM SNA AND QUICKLY CLBED TO FL310. FLT PLAN: CHANL1 DEP, GMN TRANSITION PXN2 ARR OAK. WE ARE USED TO COMPETING ON THE AIRWAY SPACE WITH ACR'S. SEVERAL ACFT RPTED TURB AT FL280, AND THE ACR Y IN FRONT OF US WAS ONE OF THEM. AS SUCH, HE REQUESTED AND WAS GRANTED A SLOWER THAN NORMAL SPD OF MACH .72. OUR CRUISE SPD TODAY WAS MACH .80. ANOTHER ACR Z BEHIND US COMPLAINED OF BUMPS AT LOWER ALTS AND I VOLUNTEERED THAT THE RIDE AT FL310 WAS FINE, SO ATC CLBED THE TFC BEHIND US TO FL310 AS WELL. AS WE PASSED GMN, I COULD SEE THE SLOWER, LOWER ACR Y JET IN FRONT OF US. THERE WAS ALMOST NO WIND THIS DAY, THE FMS RPTED 6 KTS. THE TCASII UNIT SHOWED US GAINING ON HIM QUITE QUICKLY. I KNEW THIS WOULD BE A CONFLICT AS WE WOULD BOTH BE DSNDING FOR OAK AND I WASN'T QUITE SURE HOW ATC WAS PLANNING ON SORTING OUT THE DSCNT. AS IT TURNED OUT, ABOUT 50 NM ON PXN, ATC SAW THE PROB AND SLOWED US DOWN TO MACH .75, ASKED THE JET TO SPD UP TO 'MAX FORWARD' AND WAITED. ACR Y CREPT FROM 2 NM IN FRONT OF US TO 5 NM. THEN WE WERE BOTH ISSUED DSCNTS TO MAKE STAR XING RESTRS (BORED INTXN AT 10000 FT, 250 KTS). THE JET STARTED DOWN, AND SO DID WE. AT FL260, WE FOUND HIS WAKE: WITH THE AUTOPLT ENGAGED, THE AIRPLANE SUDDENLY ROLLED 15 DEGS R. I DISCONNECTED THE AUTOPLT, COUNTERED THE ROLL AND CLBED SLIGHTLY (400 FT), THINKING WE WERE IN HIS WAKE AND COULD CLB ABOVE IT. OUT OF 200 FT, THE ROLLING AND BUCKING TREND INSTANTLY STOPPED. MY FO RESPONDED ON THE RADIO THAT WE HAD CLBED DUE TO WAKE ENCOUNTER AND WE CONTINUED DOWN AT A SLOWER RATE. I WOULD ESTIMATE ACR Y JET WAS 6-8 NM IN FRONT OF US AT THIS POINT. AFTER XING PXN VOR, WE CONTINUED DOWN AND ENCOUNTERED IT AGAIN AT FL180. THIS TIME, I OFFSET SLIGHTLY TO THE R OFF COURSE TO AVOID ANY FURTHER ENCOUNTER. AS WE SWITCHED TO NORCAL APCH, ATC QUERIED, 'I DON'T KNOW HOW YOU ARE NAVING, BUT YOU SEEM TO BE ABOUT 1 MI E OF CTRLINE.' I RESPONDED THAT WE WERE EXACTLY 1 NM E OF CTRLINE (PER PROGRAMMING) DUE TO WAKE TURB WITH THE JET PRECEDING US INTO OAK. THERE WAS SILENCE, THEN ATC ASKED, 'NOT IN MY SECTOR WAS IT?' NO, IT WAS WITH CTR, PRIOR TO HIS HANDING US OFF TO YOU. WE WERE VECTORED ONTO FINAL FOR RWY 27R, WHILE ACR Y JET WENT TO RWY 29 AND NO FURTHER INCIDENTS WERE ENCOUNTERED OR MENTIONED. LESSONS: WATCH OUT IN SMOOTH AIR FOR RELATIVELY STABLE VORTEX GENERATION AND TRY TO MAINTAIN 10 NM IN-TRAIL, VERSUS 5 NM OFFERED BY ATC, EVEN IN A 50000 LB AIRPLANE!

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.