Narrative:

We were following a B757 and were advised that we had 4 mi or greater separation. ATC wanted us to maintain 190 KTS to FAF and 170 KTS to 'MM.' we started getting hit by wake turbulence and immediately slowed to 160 KIAS to put more distance between us and the B757. Controller was talking and could not advise of our slowing airspeed. 2 mins later the controller asked us our airspeed and we said '160' KTS. He advised us in his upset tone of voice we were to hold 190 KTS and then 170 KTS. We increased our speed and landed without incident. Callback conversation with reporter revealed the following information: the reporter stated he had not intercepted the ILS GS when the plane rolled about 20 degrees with an alarming abruptness. After recovering, our response was to pull the power back and slow down to gain more distance. Tried to alert the controller but could not get a word in edge wise due to frequency congestion. The yaw and pitch and flight path displacement were minimal but the rapidity of the roll branded the event on our memory. The whole event only lasted 3-4 seconds. The PF only had partial control with aileron of the airplane roll. The reporter stated he would have told the controller earlier he could not accept the assigned speeds if he had known then what he knows now. He suggests an FAA policy of a minimum spacing criterion behind a boeing 757 be at least 5 mi.

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Original NASA ASRS Text

Title: RPTR ENCOUNTERS BOEING 757 WAKE TURB.

Narrative: WE WERE FOLLOWING A B757 AND WERE ADVISED THAT WE HAD 4 MI OR GREATER SEPARATION. ATC WANTED US TO MAINTAIN 190 KTS TO FAF AND 170 KTS TO 'MM.' WE STARTED GETTING HIT BY WAKE TURB AND IMMEDIATELY SLOWED TO 160 KIAS TO PUT MORE DISTANCE BTWN US AND THE B757. CTLR WAS TALKING AND COULD NOT ADVISE OF OUR SLOWING AIRSPD. 2 MINS LATER THE CTLR ASKED US OUR AIRSPD AND WE SAID '160' KTS. HE ADVISED US IN HIS UPSET TONE OF VOICE WE WERE TO HOLD 190 KTS AND THEN 170 KTS. WE INCREASED OUR SPD AND LANDED WITHOUT INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE HAD NOT INTERCEPTED THE ILS GS WHEN THE PLANE ROLLED ABOUT 20 DEGS WITH AN ALARMING ABRUPTNESS. AFTER RECOVERING, OUR RESPONSE WAS TO PULL THE PWR BACK AND SLOW DOWN TO GAIN MORE DISTANCE. TRIED TO ALERT THE CTLR BUT COULD NOT GET A WORD IN EDGE WISE DUE TO FREQ CONGESTION. THE YAW AND PITCH AND FLT PATH DISPLACEMENT WERE MINIMAL BUT THE RAPIDITY OF THE ROLL BRANDED THE EVENT ON OUR MEMORY. THE WHOLE EVENT ONLY LASTED 3-4 SECONDS. THE PF ONLY HAD PARTIAL CTL WITH AILERON OF THE AIRPLANE ROLL. THE RPTR STATED HE WOULD HAVE TOLD THE CTLR EARLIER HE COULD NOT ACCEPT THE ASSIGNED SPDS IF HE HAD KNOWN THEN WHAT HE KNOWS NOW. HE SUGGESTS AN FAA POLICY OF A MINIMUM SPACING CRITERION BEHIND A BOEING 757 BE AT LEAST 5 MI.

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.