B737-800 flight crew encounters B757 wake turbulence during cruise at FL350.

Attributes
ACN	707324
Time
Date	200608
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : mem.vortac
State Reference	TN
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	707324
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	707320
Events
Anomaly	inflight encounter : wake turbulence
Independent Detector	other flight crewa other flight crewb
Resolutory Action	none taken : insufficient time
Supplementary
Problem Areas	Airspace Structure Aircraft
Primary Problem	Airspace Structure

Narrative:

Approximately 50 west of mem at FL350 cruise altitude encountered moderate sudden onset turbulence of opposite track B757 at FL360 in calm air (no wind). I had a feeling it would happen as I have experienced this before. Seat belt sign on and no injuries occurred. Once again; different separation criteria must be established when there is no wind at altitude for wake avoidance. As there should also be established; near the ground for wake avoidance in calm air.

Original NASA ASRS Text

Title: B737-800 FLT CREW ENCOUNTERS B757 WAKE TURB DURING CRUISE AT FL350.

Narrative: APPROX 50 W OF MEM AT FL350 CRUISE ALT ENCOUNTERED MODERATE SUDDEN ONSET TURB OF OPPOSITE TRACK B757 AT FL360 IN CALM AIR (NO WIND). I HAD A FEELING IT WOULD HAPPEN AS I HAVE EXPERIENCED THIS BEFORE. SEAT BELT SIGN ON AND NO INJURIES OCCURRED. ONCE AGAIN; DIFFERENT SEPARATION CRITERIA MUST BE ESTABLISHED WHEN THERE IS NO WIND AT ALT FOR WAKE AVOIDANCE. AS THERE SHOULD ALSO BE ESTABLISHED; NEAR THE GND FOR WAKE AVOIDANCE IN CALM AIR.

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.