B767 flight crew encounters severe turbulence and has an altitude deviation.

Attributes
ACN	717092
Time
Date	200611
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : czqm.artcc
State Reference	NB
Altitude	msl single value : 31000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : czqm.artcc
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 120 flight time total : 10000 flight time type : 6300
ASRS Report	717092
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter : weather other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment flight crew : regained aircraft control flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Environmental Factor Weather Flight Crew Human Performance
Primary Problem	Weather

Narrative:

We crossed kanni intersection at FL310. We were talking to moncton center. We started to encounter light; occasional moderate turbulence; so we reduced our speed to .79 mach. We were IMC; and nothing was painting on the radar. Just east of kanni the turbulence became severe; and we encountered an enormous updraft; then a sudden burst of rain. There was still nothing painting on the radar. The airplane shot upward so fast through 31500 ft that the autoplt disconnected. I took over manually; reduced the thrust and was able to arrest the ascent at 31900 ft. I started to descend back to FL310 when the controller asked us to confirm our altitude. We reported moderate to severe turbulence and the updraft. We leveled off at FL310. A few mins later we requested a climb to FL350; and we did not encounter any more moderate to severe turbulence. At no time was anything observed on the radar.

Original NASA ASRS Text

Title: B767 FLT CREW ENCOUNTERS SEVERE TURB AND HAS AN ALTDEV.

Narrative: WE CROSSED KANNI INTXN AT FL310. WE WERE TALKING TO MONCTON CTR. WE STARTED TO ENCOUNTER LIGHT; OCCASIONAL MODERATE TURB; SO WE REDUCED OUR SPD TO .79 MACH. WE WERE IMC; AND NOTHING WAS PAINTING ON THE RADAR. JUST E OF KANNI THE TURB BECAME SEVERE; AND WE ENCOUNTERED AN ENORMOUS UPDRAFT; THEN A SUDDEN BURST OF RAIN. THERE WAS STILL NOTHING PAINTING ON THE RADAR. THE AIRPLANE SHOT UPWARD SO FAST THROUGH 31500 FT THAT THE AUTOPLT DISCONNECTED. I TOOK OVER MANUALLY; REDUCED THE THRUST AND WAS ABLE TO ARREST THE ASCENT AT 31900 FT. I STARTED TO DSND BACK TO FL310 WHEN THE CTLR ASKED US TO CONFIRM OUR ALT. WE RPTED MODERATE TO SEVERE TURB AND THE UPDRAFT. WE LEVELED OFF AT FL310. A FEW MINS LATER WE REQUESTED A CLB TO FL350; AND WE DID NOT ENCOUNTER ANY MORE MODERATE TO SEVERE TURB. AT NO TIME WAS ANYTHING OBSERVED ON THE RADAR.

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.