A B777 flight crew experience moderate to severe turbulence while receiving a TCASII RA.

Attributes
ACN	597790
Time
Date	200310
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : czqx.artcc
State Reference	NF
Altitude	msl single value : 35000
Environment
Weather Elements	Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : czqx.artcc tower : hou.tower
Operator	common carrier : air carrier
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : atlantic
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : czqx.artcc
Operator	common carrier : air carrier
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
ASRS Report	597790
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne critical inflight encounter : turbulence
Independent Detector	aircraft equipment : tcas
Resolutory Action	flight crew : took evasive action
Supplementary
Problem Areas	ATC Human Performance Environmental Factor Flight Crew Human Performance Airspace Structure Weather
Primary Problem	Environmental Factor

Narrative:

At FL350 approaching 40W, we passed beneath a B777 at FL360 same direction. About 10 mins later we experienced an area of moderate to severe turbulence (we later established they had the same). While entering into the most severe area we received a TA, followed the 'monitor vertical speed' then 'descend, descend.' I disengaged the autoplt to comply with the RA. Because of the turbulence, maintaining airspeed and altitude was very difficult. Airspeed fluctuated between -30K and -40K. The turbulence also made it difficult to read the instruments. The last indications we were able to see clearly was -900 ft difference. RA continued until reaching approximately FL340 then announced 'clear of conflict.'

Original NASA ASRS Text

Title: A B777 FLT CREW EXPERIENCE MODERATE TO SEVERE TURB WHILE RECEIVING A TCASII RA.

Narrative: AT FL350 APCHING 40W, WE PASSED BENEATH A B777 AT FL360 SAME DIRECTION. ABOUT 10 MINS LATER WE EXPERIENCED AN AREA OF MODERATE TO SEVERE TURB (WE LATER ESTABLISHED THEY HAD THE SAME). WHILE ENTERING INTO THE MOST SEVERE AREA WE RECEIVED A TA, FOLLOWED THE 'MONITOR VERT SPD' THEN 'DSND, DSND.' I DISENGAGED THE AUTOPLT TO COMPLY WITH THE RA. BECAUSE OF THE TURB, MAINTAINING AIRSPD AND ALT WAS VERY DIFFICULT. AIRSPD FLUCTUATED BTWN -30K AND -40K. THE TURB ALSO MADE IT DIFFICULT TO READ THE INSTS. THE LAST INDICATIONS WE WERE ABLE TO SEE CLRLY WAS -900 FT DIFFERENCE. RA CONTINUED UNTIL REACHING APPROX FL340 THEN ANNOUNCED 'CLR OF CONFLICT.'

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.