B737-700 flight crew encounters wake turbulence on final to sna.

Attributes
ACN	717894
Time
Date	200611
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sna.airport
State Reference	CA
Altitude	agl bound lower : 50 msl single value : 100
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : sna.tower
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 19r other Other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : sna.tower
Make Model Name	B757 Undifferentiated or Other Model
Flight Phase	landing : roll
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 7000
ASRS Report	717894
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	inflight encounter : wake turbulence
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment flight crew : executed go around
Supplementary
Problem Areas	Environmental Factor
Primary Problem	Environmental Factor

Narrative:

On downwind; tower pointed out the B757 traffic that we would be following. We were at flaps 5 and slowing to 168 KTS. We called the traffic and field 'in sight;' cleared for the visual. As the traffic passed our 3 O'clock we began our turn to base. Gear down and flaps to 15 then 25. On final outside of lemon (final approach fix) flaps to 40 and at 133 KTS (flaps target speed). On localizer glideslope we continued the visual approach. The traffic cleared the runway. As we passed the ILS minimums of 252 ft we began to encounter wake turbulence. As we attempted to continue to landing the turbulence got worse. At between 100 to 50 ft I elected to execute a manual go around. We maintained VMC and requested vectors back to final for another visual approach. The wind was very light to calm. Our vref was 128 KTS for flap 40 degrees and target speed of 133 KTS. Approach and landing with no further incidents.

Original NASA ASRS Text

Title: B737-700 FLT CREW ENCOUNTERS WAKE TURB ON FINAL TO SNA.

Narrative: ON DOWNWIND; TWR POINTED OUT THE B757 TFC THAT WE WOULD BE FOLLOWING. WE WERE AT FLAPS 5 AND SLOWING TO 168 KTS. WE CALLED THE TFC AND FIELD 'IN SIGHT;' CLEARED FOR THE VISUAL. AS THE TFC PASSED OUR 3 O'CLOCK WE BEGAN OUR TURN TO BASE. GEAR DOWN AND FLAPS TO 15 THEN 25. ON FINAL OUTSIDE OF LEMON (FINAL APCH FIX) FLAPS TO 40 AND AT 133 KTS (FLAPS TARGET SPD). ON LOC GLIDESLOPE WE CONTINUED THE VISUAL APCH. THE TFC CLRED THE RWY. AS WE PASSED THE ILS MINIMUMS OF 252 FT WE BEGAN TO ENCOUNTER WAKE TURB. AS WE ATTEMPTED TO CONTINUE TO LNDG THE TURB GOT WORSE. AT BETWEEN 100 TO 50 FT I ELECTED TO EXECUTE A MANUAL GAR. WE MAINTAINED VMC AND REQUESTED VECTORS BACK TO FINAL FOR ANOTHER VISUAL APCH. THE WIND WAS VERY LIGHT TO CALM. OUR VREF WAS 128 KTS FOR FLAP 40 DEGS AND TARGET SPD OF 133 KTS. APCH AND LNDG WITH NO FURTHER INCIDENTS.

Data retrieved from NASA's ASRS site as of January 2009 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.