A boeing 757 flight crew climbed above assigned altitude after descent near giber intersection.

Attributes
ACN	444050
Time
Date	199907
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	intersection : giber
State Reference	IL
Altitude	msl bound lower : 33000 msl bound upper : 33300
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	Cessna Aircraft Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 12000 flight time type : 600
ASRS Report	444050
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

Descent from FL410-FL330 at leveloff (FL330) I noticed aircraft advancing power and climbing. PNF called climbing. Copilot attempted to correct, I didn't feel the correction was fast enough so I disconnected the autoplt and corrected aircraft pitch to maintain FL330. Gain of +300 ft was noted. I do not know why the aircraft climbed. Copilot was operating on autoplt, had FL330 in altitude select window and was operating by SOP's.

Original NASA ASRS Text

Title: A BOEING 757 FLC CLBED ABOVE ASSIGNED ALT AFTER DSCNT NEAR GIBER INTXN.

Narrative: DSCNT FROM FL410-FL330 AT LEVELOFF (FL330) I NOTICED ACFT ADVANCING PWR AND CLBING. PNF CALLED CLBING. COPLT ATTEMPTED TO CORRECT, I DIDN'T FEEL THE CORRECTION WAS FAST ENOUGH SO I DISCONNECTED THE AUTOPLT AND CORRECTED ACFT PITCH TO MAINTAIN FL330. GAIN OF +300 FT WAS NOTED. I DO NOT KNOW WHY THE ACFT CLBED. COPLT WAS OPERATING ON AUTOPLT, HAD FL330 IN ALT SELECT WINDOW AND WAS OPERATING BY SOP'S.

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.