A B737-700 pilot reported deviating from ATC assigned speed to increase spacing behind a B757 that w...

Attributes
ACN	1027399
Time
Date	201208
Local Time Of Day	0601-1200
Place
Locale Reference	ATL.Airport
State Reference	GA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	STAR ERLIN 9 RNAV
Flight Plan	IFR
Aircraft 2
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 185
Events
Anomaly	Deviation - Procedural Clearance Deviation - Speed All Types Inflight Event / Encounter Wake Vortex Encounter

Narrative:

While on the erlin 9 RNAV arrival into atlanta; encountered three wake turbulence events after which I asked if we were following a heavy. ATC responded that we were preceded by a B757. After passing nofiv and clearance to a lower altitude I asked the pilot flying to shallow the descent to avoid further wake encounter. Once the B757 turned base we were able to keep traffic in sight and in our base turn with a speed assignment of 170 KTS; we were asked to follow the B757 to the airport but maintain present heading and plan a turn to join final. ATC provided heading to join final and cleared us for a visual approach call the tower at ajaay. At this point we continued to slow and configure due to being above glide slope. Before reaching ajaay; approach asked our speed and instructed aircraft behind us to slow. I believe that ATC was planning for us to keep our 170 KTS until reaching the marker as stated in safety alert [bulletin]. Our clearance was cleared visual approach with no stated speed to the marker. Believe I may have become too conservative in my approach to wake avoidance. With traffic volume into atl should have done a better job with ATC communication.

Original NASA ASRS Text

Title: A B737-700 pilot reported deviating from ATC assigned speed to increase spacing behind a B757 that was causing some wake turbulence.

Narrative: While on the ERLIN 9 RNAV Arrival into Atlanta; encountered three wake turbulence events after which I asked if we were following a Heavy. ATC responded that we were preceded by a B757. After passing NOFIV and clearance to a lower altitude I asked the pilot flying to shallow the descent to avoid further wake encounter. Once the B757 turned base we were able to keep traffic in sight and in our base turn with a speed assignment of 170 KTS; we were asked to follow the B757 to the airport but maintain present heading and plan a turn to join final. ATC provided heading to join final and cleared us for a visual approach call the Tower at AJAAY. At this point we continued to slow and configure due to being above glide slope. Before reaching AJAAY; Approach asked our speed and instructed aircraft behind us to slow. I believe that ATC was planning for us to keep our 170 KTS until reaching the marker as stated in Safety Alert [bulletin]. Our clearance was cleared visual approach with no stated speed to the marker. Believe I may have become too conservative in my approach to wake avoidance. With traffic volume into ATL should have done a better job with ATC communication.

Data retrieved from NASA's ASRS site as of July 2013 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.