Narrative:

Bay put us on a base leg at 6000 ft 8 mi from runway 19L. I asked if this was vectors to ILS ('yes') and was he going to put us on the GS ('maybe'). Then he asked if we could get down and offered to break us out for it would either be this slam-dunk to the ILS or a 20 mi final. We accepted the slam-dunk. It was a mistake. We had to dive to make it. At about 4 mi final we encountered serious wake turbulence from a B757 4 mi ahead that the controller didn't bother to tell us about until we were cleared for approach. Bay does this frequently, ie, forgets to tell about a wake generator. Also, they frequently put you on the ILS way above the GS. That is illegal and unsafe. Callback conversation with reporter revealed the following information: reporter participated in the wake turbulence structured callback program. Reporter feels that TRACON induced the situation by giving a high steep approach to them with little separation from proceeding aircraft. It was not known to flight crew that the aircraft they were following was a B757 until they were on tower frequency. Because the approach was close in, it forced them to be steep with an idle power setting. This meant that they didn't have a stabilized power setting which would help them recover quickly if they should have an upset situation. Even with a high steep descent, the reporter encountered wake turbulence. The turbulence wasn't too severe and only lasted 3-4 seconds.

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Original NASA ASRS Text

Title: ACFT EXPERIENCES WAKE TURB DURING STEEP DSCNT INTO SFO.

Narrative: BAY PUT US ON A BASE LEG AT 6000 FT 8 MI FROM RWY 19L. I ASKED IF THIS WAS VECTORS TO ILS ('YES') AND WAS HE GOING TO PUT US ON THE GS ('MAYBE'). THEN HE ASKED IF WE COULD GET DOWN AND OFFERED TO BREAK US OUT FOR IT WOULD EITHER BE THIS SLAM-DUNK TO THE ILS OR A 20 MI FINAL. WE ACCEPTED THE SLAM-DUNK. IT WAS A MISTAKE. WE HAD TO DIVE TO MAKE IT. AT ABOUT 4 MI FINAL WE ENCOUNTERED SERIOUS WAKE TURB FROM A B757 4 MI AHEAD THAT THE CTLR DIDN'T BOTHER TO TELL US ABOUT UNTIL WE WERE CLRED FOR APCH. BAY DOES THIS FREQUENTLY, IE, FORGETS TO TELL ABOUT A WAKE GENERATOR. ALSO, THEY FREQUENTLY PUT YOU ON THE ILS WAY ABOVE THE GS. THAT IS ILLEGAL AND UNSAFE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN THE WAKE TURB STRUCTURED CALLBACK PROGRAM. RPTR FEELS THAT TRACON INDUCED THE SIT BY GIVING A HIGH STEEP APCH TO THEM WITH LITTLE SEPARATION FROM PROCEEDING ACFT. IT WAS NOT KNOWN TO FLC THAT THE ACFT THEY WERE FOLLOWING WAS A B757 UNTIL THEY WERE ON TWR FREQ. BECAUSE THE APCH WAS CLOSE IN, IT FORCED THEM TO BE STEEP WITH AN IDLE PWR SETTING. THIS MEANT THAT THEY DIDN'T HAVE A STABILIZED PWR SETTING WHICH WOULD HELP THEM RECOVER QUICKLY IF THEY SHOULD HAVE AN UPSET SIT. EVEN WITH A HIGH STEEP DSCNT, THE RPTR ENCOUNTERED WAKE TURB. THE TURB WASN'T TOO SEVERE AND ONLY LASTED 3-4 SECONDS.

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.