Medium large transport crew had altitude deviation due to thunderstorm WX encounter.

Attributes
ACN	473830
Time
Date	200005
Day	Wed
Local Time Of Day	1801 To 2400
Place
State Reference	NJ
Altitude	msl bound lower : 25700 msl bound upper : 26500
Environment
Flight Conditions	IMC
Weather Elements	Thunderstorm Turbulence
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 6000 flight time type : 1800
ASRS Report	473830
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude none taken : detected after the fact
Supplementary
Problem Areas	FAA ATC Human Performance Weather
Primary Problem	Weather

Narrative:

We were not painting any severe WX on radar. Climbing in WX, ATC told us to do a 360 degree turn because washington would not accept us. 90 degrees into turn we started seeing WX on radar and asked ATC if we could reverse turn to avoid WX. They approved. As we turned back to avoid WX we encountered turbulence that caused airplane to deviate from -300 ft to +500 ft from assigned altitude. Asked center for a block altitude due to inability to maintain assigned altitude. Center said they could not approve, but no one was around us.

Original NASA ASRS Text

Title: MLG CREW HAD ALTDEV DUE TO TSTM WX ENCOUNTER.

Narrative: WE WERE NOT PAINTING ANY SEVERE WX ON RADAR. CLBING IN WX, ATC TOLD US TO DO A 360 DEG TURN BECAUSE WASHINGTON WOULD NOT ACCEPT US. 90 DEGS INTO TURN WE STARTED SEEING WX ON RADAR AND ASKED ATC IF WE COULD REVERSE TURN TO AVOID WX. THEY APPROVED. AS WE TURNED BACK TO AVOID WX WE ENCOUNTERED TURB THAT CAUSED AIRPLANE TO DEVIATE FROM -300 FT TO +500 FT FROM ASSIGNED ALT. ASKED CTR FOR A BLOCK ALT DUE TO INABILITY TO MAINTAIN ASSIGNED ALT. CTR SAID THEY COULD NOT APPROVE, BUT NO ONE WAS AROUND US.

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.