Narrative:

It was a beautiful evening for flying. We had the chicago skyline in sight from a hundred miles away! There was not so much as a single ripple in the air as we approached the world's busiest from the northwest. Landing was to be on 9R, wind was 090 at 8, temperature 59 degrees. (Landing into the wind at chicago???) the first officer was flying, and I was enjoying watching for traffic. We were on a 180 degree heading when we spotted the traffic we were to follow widebody transport. I believe we were right at 3 mi in trail. I remember thinking about reading somewhere of reports of wake turbulence when following wdbs, but we didn't feel a thing. I don't specifically recall our altitude or distance out when the widebody transport touched down, but from experience at ord I know we would have gotten a speed reduction if our sep had decreased. I believe their T/D was 1000-1500' down the runway--right in the middle of the T/D zone--and they were clear of the runway at the high speed in plenty of time for our arrival. We were configured for landing and within 10 KTS of approach speed as we passed through 1000'. First officer had it wired all the way in. Since we had been cleared for an ILS I called decision height at 200'. At about 150', the vortices from the widebody transport were encountered and the aircraft began a rapid roll to the right. The disturbed air and rolling moment continued to below 50', though with less intensity than the first jolt. At the first bump, first officer of course applied substantial aileron estimated at 75% of available roll control and added power to stabilize the flight path. While I began thinking in terms of a go around, the rolling moments decreased and then stopped, and first officer was able to salvage a smooth T/D and rollout. After parking at the gate and completing the shutdown checklist, I got off the aircraft as soon as I could, but a couple of the passenger remarked about the heavy gust on approach. (I wanted to talk to the widebody transport crew, which was why I was in a hurry to leave.) the fact that 2 passenger out of only a half dozen I saw deplane made a remark is significant. I was able to make it to the widebody transport arrival gate before the crew left the aircraft. Captain and check airman and first officer confirmed that their arrival confign was normal, they were not above the G/south on short final, they touched down in the middle of the T/D zone, and if anything they had maintained 170 KTS to a bit inside the OM. I draw the following conclusions: 1) I will in the future be particularly alert to wake turbulence encounters when following widebody transport aircraft. 2) I will in the future not hesitate to go around if the flight path becomes unstabilized at a low altitude. 3) it is my opinion that narrow body sep standards are not adequate when following widebody transport aircraft. 4) get the word out! The medium large transport operating manual talks about non-linear roll response, tab driven ailerons and wake turbulence encounters. A statement should be added to emphasize that particular caution is advised when following a widebody transport. An article in flight deck and statements in operations bulletins and base newsletters should be made to alert medium large transport crews. 5) ask for a runway with a strong gusty crosswind.

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Original NASA ASRS Text

Title: MLG FLT CREW ENCOUNTERS SEVERE WAKE TURBULENCE JUST PRIOR TO TOUCH DOWN FOLLOWING WDB ACFT.

Narrative: IT WAS A BEAUTIFUL EVENING FOR FLYING. WE HAD THE CHICAGO SKYLINE IN SIGHT FROM A HUNDRED MILES AWAY! THERE WAS NOT SO MUCH AS A SINGLE RIPPLE IN THE AIR AS WE APCHED THE WORLD'S BUSIEST FROM THE NW. LNDG WAS TO BE ON 9R, WIND WAS 090 AT 8, TEMP 59 DEGS. (LNDG INTO THE WIND AT CHICAGO???) THE F/O WAS FLYING, AND I WAS ENJOYING WATCHING FOR TFC. WE WERE ON A 180 DEG HDG WHEN WE SPOTTED THE TFC WE WERE TO FOLLOW WDB. I BELIEVE WE WERE RIGHT AT 3 MI IN TRAIL. I REMEMBER THINKING ABOUT READING SOMEWHERE OF RPTS OF WAKE TURB WHEN FOLLOWING WDBS, BUT WE DIDN'T FEEL A THING. I DON'T SPECIFICALLY RECALL OUR ALT OR DISTANCE OUT WHEN THE WDB TOUCHED DOWN, BUT FROM EXPERIENCE AT ORD I KNOW WE WOULD HAVE GOTTEN A SPD REDUCTION IF OUR SEP HAD DECREASED. I BELIEVE THEIR T/D WAS 1000-1500' DOWN THE RWY--RIGHT IN THE MIDDLE OF THE T/D ZONE--AND THEY WERE CLR OF THE RWY AT THE HIGH SPD IN PLENTY OF TIME FOR OUR ARR. WE WERE CONFIGURED FOR LNDG AND WITHIN 10 KTS OF APCH SPD AS WE PASSED THROUGH 1000'. F/O HAD IT WIRED ALL THE WAY IN. SINCE WE HAD BEEN CLRED FOR AN ILS I CALLED DECISION HEIGHT AT 200'. AT ABOUT 150', THE VORTICES FROM THE WDB WERE ENCOUNTERED AND THE ACFT BEGAN A RAPID ROLL TO THE RIGHT. THE DISTURBED AIR AND ROLLING MOMENT CONTINUED TO BELOW 50', THOUGH WITH LESS INTENSITY THAN THE FIRST JOLT. AT THE FIRST BUMP, F/O OF COURSE APPLIED SUBSTANTIAL AILERON ESTIMATED AT 75% OF AVAILABLE ROLL CTL AND ADDED PWR TO STABILIZE THE FLT PATH. WHILE I BEGAN THINKING IN TERMS OF A GAR, THE ROLLING MOMENTS DECREASED AND THEN STOPPED, AND F/O WAS ABLE TO SALVAGE A SMOOTH T/D AND ROLLOUT. AFTER PARKING AT THE GATE AND COMPLETING THE SHUTDOWN CHKLIST, I GOT OFF THE ACFT AS SOON AS I COULD, BUT A COUPLE OF THE PAX REMARKED ABOUT THE HEAVY GUST ON APCH. (I WANTED TO TALK TO THE WDB CREW, WHICH WAS WHY I WAS IN A HURRY TO LEAVE.) THE FACT THAT 2 PAX OUT OF ONLY A HALF DOZEN I SAW DEPLANE MADE A REMARK IS SIGNIFICANT. I WAS ABLE TO MAKE IT TO THE WDB ARR GATE BEFORE THE CREW LEFT THE ACFT. CAPT AND CHK AIRMAN AND F/O CONFIRMED THAT THEIR ARR CONFIGN WAS NORMAL, THEY WERE NOT ABOVE THE G/S ON SHORT FINAL, THEY TOUCHED DOWN IN THE MIDDLE OF THE T/D ZONE, AND IF ANYTHING THEY HAD MAINTAINED 170 KTS TO A BIT INSIDE THE OM. I DRAW THE FOLLOWING CONCLUSIONS: 1) I WILL IN THE FUTURE BE PARTICULARLY ALERT TO WAKE TURB ENCOUNTERS WHEN FOLLOWING WDB ACFT. 2) I WILL IN THE FUTURE NOT HESITATE TO GO AROUND IF THE FLT PATH BECOMES UNSTABILIZED AT A LOW ALT. 3) IT IS MY OPINION THAT NARROW BODY SEP STANDARDS ARE NOT ADEQUATE WHEN FOLLOWING WDB ACFT. 4) GET THE WORD OUT! THE MLG OPERATING MANUAL TALKS ABOUT NON-LINEAR ROLL RESPONSE, TAB DRIVEN AILERONS AND WAKE TURB ENCOUNTERS. A STATEMENT SHOULD BE ADDED TO EMPHASIZE THAT PARTICULAR CAUTION IS ADVISED WHEN FOLLOWING A WDB. AN ARTICLE IN FLT DECK AND STATEMENTS IN OPS BULLETINS AND BASE NEWSLETTERS SHOULD BE MADE TO ALERT MLG CREWS. 5) ASK FOR A RWY WITH A STRONG GUSTY XWIND.

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.