B757 flight crew encounters light to moderate turbulence at FL390 and requests FL370. Turbulence is ...

Narrative:

Enroute at FL390 seat belt sign was on with continuous lt(light)-mod(moderate) chop. Requested altitude change. Cleared to FL370. Ride rapidly transitioned to mod-svr(severe) turbulence. ATC advised and we requested immediate further descent to FL270. ATC said something about us to expect lower in xx minutes. Ride continued to deteriorate to severe turbulence; ATC advised; and we requested turn for descent. We were cleared to descend 1000 feet. We did and requested further descent. I noted 160+ kt wind on the tail. First officer again requested descent and advised ATC of ride conditions; again given 1000 foot descent. I could not see other aircraft painting on TCAS below. We declared an emergency and advised ATC of our further descent. We were then cleared to FL270. Ride transitioned from severe turbulence out of FL320. Removing the aircraft from severe turbulence was our primary effort. This process required first officer's 100% attention. This primary duty precluded other things such as cabin announcement; as the seat belt sign was fortunately already on. My impression was that ATC treated our transmissions as routine; and too much and time effort was spent requesting altitude change after reporting severe turbulence. We never did get clearance. We declared an emergency and stated intentions. After level off I determined there were no injuries; no apparent aircraft damage; briefed passengers via PA and reported to dispatch and maintenance. After level off in our sector; and after hand off to another sector; we were never queried with usual post emergency declaration questions; such as if assist needed; number of souls; if were still emergency status; etc. I do not know if ATC was unresponsive to our declaration in other unobserved areas.

Original NASA ASRS Text

Title: B757 Flight Crew encounters light to moderate turbulence at FL390 and requests FL370. Turbulence is worse lower and further descent is requested which is slow in coming. This results in an emergency declaration and descent to FL310 to avoid severe turbulence.

Narrative: Enroute at FL390 seat belt sign was on with continuous LT(Light)-MOD(Moderate) chop. Requested altitude change. Cleared to FL370. Ride rapidly transitioned to MOD-SVR(Severe) turbulence. ATC advised and we requested immediate further descent to FL270. ATC said something about us to expect lower in xx minutes. Ride continued to deteriorate to severe turbulence; ATC advised; and we requested turn for descent. We were cleared to descend 1000 feet. We did and requested further descent. I noted 160+ Kt Wind on the tail. F/O again requested descent and advised ATC of ride conditions; again given 1000 foot descent. I could not see other aircraft painting on TCAS below. We declared an emergency and advised ATC of our further descent. We were then cleared to FL270. Ride transitioned from severe turbulence out of FL320. Removing the aircraft from severe turbulence was our primary effort. This process required F/O's 100% attention. This primary duty precluded other things such as cabin announcement; as the Seat Belt sign was fortunately already ON. My impression was that ATC treated our transmissions as routine; and too much and time effort was spent requesting altitude change after reporting severe turbulence. We never did get clearance. We declared an emergency and stated intentions. After level off I determined there were no injuries; no apparent aircraft damage; briefed passengers via PA and reported to Dispatch and Maintenance. After level off in our sector; and after hand off to another sector; we were never queried with usual post emergency declaration questions; such as if assist needed; number of souls; if were still emergency status; etc. I do not know if ATC was unresponsive to our declaration in other unobserved areas.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	862717
Time
Date	200912
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Experience	Flight Crew Last 90 Days 240 Flight Crew Total 12000 Flight Crew Type 5000
Person 2
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 170 Flight Crew Total 7000 Flight Crew Type 2000
Events
Anomaly	Inflight Event / Encounter Weather / Turbulence

B757 flight crew encounters light to moderate turbulence at FL390 and requests FL370. Turbulence is worse lower and further descent is requested which is slow in coming. This results in an emergency declaration and descent to FL310 to avoid severe turbulence.