Flight crew of widebody transport cleared down to FL370 encountered intolerable turbulence. Unable to contact ARTCC. Made unauthorized climb back to clear air. At 37500' ARTCC controller gave clearance to FL390.

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Attributes
ACN	178597
Time
Date	199105
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : bwf
State Reference	MN
Altitude	msl bound lower : 37000 msl bound upper : 37500
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : instrument
Experience	flight time last 90 days : 45 flight time total : 14112 flight time type : 3268
ASRS Report	178597
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : far non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATC direct us to descend from 39000' on top to 37000', which put us in overcast. Upon reaching 37000', we encountered turbulence which was greater than moderate, but less than severe. We requested clearance back to 39000', but were told to contact ZMP on another frequency. Because of congestion on the new frequency, we were unable to contact ATC with our request for 39000', so I began an unauthorized climb in an attempt to get out of the turbulence. At approximately 37500', ATC contacted us and gave us clearance to 39000' where the conditions improved. I don't believe that my altitude deviation presented a problem to the controllers, nor do I think they noticed it. In retrospect, I probably should have declared an emergency upon leaving 37000', but since we were unable to communicate and were eventually cleared to 39000', it seems to be a moot point. The major problem here seems to be overworked controllers and limited airspace. Perhaps with today's technology, the midflt levels (FL380, FL400, etc) could be opened up to allow ATC more flexibility in handling these situations.

Original NASA ASRS Text

Title: FLT CREW OF WDB CLEARED DOWN TO FL370 ENCOUNTERED INTOLERABLE TURBULENCE. UNABLE TO CONTACT ARTCC. MADE UNAUTH CLIMB BACK TO CLEAR AIR. AT 37500' ARTCC CTLR GAVE CLRNC TO FL390.

Narrative: ATC DIRECT US TO DSND FROM 39000' ON TOP TO 37000', WHICH PUT US IN OVCST. UPON REACHING 37000', WE ENCOUNTERED TURB WHICH WAS GREATER THAN MODERATE, BUT LESS THAN SEVERE. WE REQUESTED CLRNC BACK TO 39000', BUT WERE TOLD TO CONTACT ZMP ON ANOTHER FREQ. BECAUSE OF CONGESTION ON THE NEW FREQ, WE WERE UNABLE TO CONTACT ATC WITH OUR REQUEST FOR 39000', SO I BEGAN AN UNAUTH CLB IN AN ATTEMPT TO GET OUT OF THE TURB. AT APPROX 37500', ATC CONTACTED US AND GAVE US CLRNC TO 39000' WHERE THE CONDITIONS IMPROVED. I DON'T BELIEVE THAT MY ALT DEVIATION PRESENTED A PROB TO THE CTLRS, NOR DO I THINK THEY NOTICED IT. IN RETROSPECT, I PROBABLY SHOULD HAVE DECLARED AN EMER UPON LEAVING 37000', BUT SINCE WE WERE UNABLE TO COMMUNICATE AND WERE EVENTUALLY CLRED TO 39000', IT SEEMS TO BE A MOOT POINT. THE MAJOR PROB HERE SEEMS TO BE OVERWORKED CTLRS AND LIMITED AIRSPACE. PERHAPS WITH TODAY'S TECHNOLOGY, THE MIDFLT LEVELS (FL380, FL400, ETC) COULD BE OPENED UP TO ALLOW ATC MORE FLEXIBILITY IN HANDLING THESE SITUATIONS.

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.