Narrative:

Following an airbus A320 into bos for an ILS runway 4R approach, with very smooth flight conditions, 10 mi behind the airbus (as shown on TCASII and as told by approach control), we encountered the wake of the A320. My aircraft was on the autoplt, about 10000 ft MSL, when the wings rolled sharply to the left about 30 degrees, and the nose pitched down 3 degrees. Our indicated airspeed was 240 KTS at the time. About 10 seconds later we received a second, similar jolt. The passenger were concerned, as relayed by our flight attendants, no injuries occurred. Aircraft control was regained after only a few seconds after the upsets occurred, by disconnecting the autoplt and hand flying the aircraft. Conclusion: wake turbulence separation criteria is inadequate, and we need to increase the standard minimum separation on approach and departure. The B757 should be the same as a heavy. Also, additional encounters behind the A320 were avoided (I'll never really know) by flying the approach 1 DOT high on the GS. Over the course of the approach, the distance behind the A320 slowly closed from 10 mi to 6 mi. Approach control routinely informs pilots they are following a heavy or B757 too late to request additional separation. We need to fix this. Callback conversation with reporter revealed the following information: the reporter has had a number of wake encounters, but after this one he has decided that he will not routinely assume that the distance separation given in the wake separation guidelines is sufficient. He had already had several bad experiences with wake encounters during departures and he now insists on both a distance as well as a time elapsed separation. The captain said that he does not think that the controllers know about how calm winds and other stable conditions can make the wake much more persistent in some cases. He said that the controllers should have to, at least, view a wake turbulence video to gain greater understanding of the problem. He feels that the problem of wake disturbances is growing.

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Original NASA ASRS Text

Title: AN ACR B727 FLC HITS THE WAKE OF AN A320 10 NM AHEAD OF THEM AND THEY ROLLED 30 DEGS TO THE L AND PITCHED DOWN 3 DEGS. THIS HAPPENED TWICE AND AFTER THE SECOND ENCOUNTER THE FLC STAYED HIGH ON APCH TO AVOID THE WAKE.

Narrative: FOLLOWING AN AIRBUS A320 INTO BOS FOR AN ILS RWY 4R APCH, WITH VERY SMOOTH FLT CONDITIONS, 10 MI BEHIND THE AIRBUS (AS SHOWN ON TCASII AND AS TOLD BY APCH CTL), WE ENCOUNTERED THE WAKE OF THE A320. MY ACFT WAS ON THE AUTOPLT, ABOUT 10000 FT MSL, WHEN THE WINGS ROLLED SHARPLY TO THE L ABOUT 30 DEGS, AND THE NOSE PITCHED DOWN 3 DEGS. OUR INDICATED AIRSPD WAS 240 KTS AT THE TIME. ABOUT 10 SECONDS LATER WE RECEIVED A SECOND, SIMILAR JOLT. THE PAX WERE CONCERNED, AS RELAYED BY OUR FLT ATTENDANTS, NO INJURIES OCCURRED. ACFT CTL WAS REGAINED AFTER ONLY A FEW SECONDS AFTER THE UPSETS OCCURRED, BY DISCONNECTING THE AUTOPLT AND HAND FLYING THE ACFT. CONCLUSION: WAKE TURB SEPARATION CRITERIA IS INADEQUATE, AND WE NEED TO INCREASE THE STANDARD MINIMUM SEPARATION ON APCH AND DEP. THE B757 SHOULD BE THE SAME AS A HVY. ALSO, ADDITIONAL ENCOUNTERS BEHIND THE A320 WERE AVOIDED (I'LL NEVER REALLY KNOW) BY FLYING THE APCH 1 DOT HIGH ON THE GS. OVER THE COURSE OF THE APCH, THE DISTANCE BEHIND THE A320 SLOWLY CLOSED FROM 10 MI TO 6 MI. APCH CTL ROUTINELY INFORMS PLTS THEY ARE FOLLOWING A HVY OR B757 TOO LATE TO REQUEST ADDITIONAL SEPARATION. WE NEED TO FIX THIS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR HAS HAD A NUMBER OF WAKE ENCOUNTERS, BUT AFTER THIS ONE HE HAS DECIDED THAT HE WILL NOT ROUTINELY ASSUME THAT THE DISTANCE SEPARATION GIVEN IN THE WAKE SEPARATION GUIDELINES IS SUFFICIENT. HE HAD ALREADY HAD SEVERAL BAD EXPERIENCES WITH WAKE ENCOUNTERS DURING DEPS AND HE NOW INSISTS ON BOTH A DISTANCE AS WELL AS A TIME ELAPSED SEPARATION. THE CAPT SAID THAT HE DOES NOT THINK THAT THE CTLRS KNOW ABOUT HOW CALM WINDS AND OTHER STABLE CONDITIONS CAN MAKE THE WAKE MUCH MORE PERSISTENT IN SOME CASES. HE SAID THAT THE CTLRS SHOULD HAVE TO, AT LEAST, VIEW A WAKE TURB VIDEO TO GAIN GREATER UNDERSTANDING OF THE PROB. HE FEELS THAT THE PROB OF WAKE DISTURBANCES IS GROWING.

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.