Altitude deviation during cruise climb.

Attributes
ACN	302680
Time
Date	199504
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : aus
State Reference	TX
Altitude	msl bound lower : 20000 msl bound upper : 21000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : cfi pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 2500 flight time type : 500
ASRS Report	302680
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were level at 19000 ft and requested 21000 ft from center. The captain (PNF) read back 21000 ft and inputted into the altitude selector. Passing through 20600 ft, center asked us what altitude we were at. We informed them 20600 ft. They responded that we were only cleared to 20000 ft. We descended back to 20000 ft without incident. Although center feels they cleared us to 20000 ft. I feel he said 21000 ft. The only reason I can feel we mistook his clearance (if we did) was our concern for building cumulus ahead of us that we were trying to get above.

Original NASA ASRS Text

Title: ALTDEV DURING CRUISE CLB.

Narrative: WE WERE LEVEL AT 19000 FT AND REQUESTED 21000 FT FROM CTR. THE CAPT (PNF) READ BACK 21000 FT AND INPUTTED INTO THE ALT SELECTOR. PASSING THROUGH 20600 FT, CTR ASKED US WHAT ALT WE WERE AT. WE INFORMED THEM 20600 FT. THEY RESPONDED THAT WE WERE ONLY CLRED TO 20000 FT. WE DSNDED BACK TO 20000 FT WITHOUT INCIDENT. ALTHOUGH CTR FEELS THEY CLRED US TO 20000 FT. I FEEL HE SAID 21000 FT. THE ONLY REASON I CAN FEEL WE MISTOOK HIS CLRNC (IF WE DID) WAS OUR CONCERN FOR BUILDING CUMULUS AHEAD OF US THAT WE WERE TRYING TO GET ABOVE.

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.