A ce-501 encountered severe turbulence for one minute at FL350 and advised ATC they were unable to m...

Attributes
ACN	1039336
Time
Date	201209
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Citation I/SP (C501)
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Pilot Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 8600 Flight Crew Type 25
Person 2
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 25 Flight Crew Total 13800 Flight Crew Type 600
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Weather / Turbulence

Narrative:

Level at FL350 en route we were on a vector from ATC to avoid the area of buildups ahead of us. We were in instrument conditions when we started to encounter severe turbulence with downdrafts that decreased our altitude to about 34;650 ft on the altimeter. I was going to disconnect the autopilot; but the PIC advised against it and said to let it ride it out and then he informed ATC that we were unable to maintain our rvsm assigned altitude of FL350. ATC then assigned us a block altitude of FL340-350 and advised us we should be exiting the weather soon. Our onboard weather avoidance equipment did not show any activity at our altitude and position and because of the IMC conditions we were unable to visually locate any activity. Shortly thereafter we exited the weather in to VFR conditions.

Original NASA ASRS Text

Title: A CE-501 encountered severe turbulence for one minute at FL350 and advised ATC they were unable to maintain RVSM because of altitude variations up to 400 FT.

Narrative: Level at FL350 en route we were on a vector from ATC to avoid the area of buildups ahead of us. We were in instrument conditions when we started to encounter severe turbulence with downdrafts that decreased our altitude to about 34;650 FT on the altimeter. I was going to disconnect the autopilot; but the PIC advised against it and said to let it ride it out and then he informed ATC that we were unable to maintain our RVSM assigned altitude of FL350. ATC then assigned us a block altitude of FL340-350 and advised us we should be exiting the weather soon. Our onboard weather avoidance equipment did not show any activity at our altitude and position and because of the IMC conditions we were unable to visually locate any activity. Shortly thereafter we exited the weather in to VFR conditions.

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.

A ce-501 encountered severe turbulence for one minute at FL350 and advised ATC they were unable to maintain rvsm because of altitude variations up to 400 ft.