A320 crew had an altitude overshot in ord class B.

Attributes
ACN	512580
Time
Date	200105
Day	Tue
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 6700
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : hnl.tower
Operator	common carrier : air carrier
Make Model Name	A320
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time type : 3515
ASRS Report	512580
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : published procedure non adherence : company policies non adherence : far non adherence : clearance other anomaly other
Resolutory Action	controller : issued alert none taken : anomaly accepted
Consequence	other
Miss Distance	horizontal : 0 vertical : 1000
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared direct ord descending to 7000 ft. I was the PNF and the first officer was the PF. The first officer disengaged the aircraft and selected vs on the FCU himself. ATC gave us a turn to the downwind and, while I was sequencing the FMC for the approach, the first officer selected open des on the FCU (non SOP). I believe he inadvertently changed the altitude to 6000 ft and neither one of us noticed the altitude change. I was distracted with the FMC and he was distracted by hand flying while changing the FCU. Going thru 6700 ft ATC asked about our cleared altitude. At the same time we had a TCASII traffic alert for an aircraft 1600 ft below. I stated we were cleared to 6000 ft and ATC stated we were cleared to 7000 ft but continue to 6000 ft. I should have emphasized to the first officer to call for FCU changes while hand flying per SOP. No loss of separation occurred. It only spent about 7-8 seconds to sequence the FMC for the approach and in that short time the error occurred. I've been a captain on the A320 for almost 7 years and this is the first time an error like this occurred. I also think a better design for the FCU would be to have a separate switch from the altitude selector to change descent modes (like flight crewh on the 767.)

Original NASA ASRS Text

Title: A320 CREW HAD AN ALT OVERSHOT IN ORD CLASS B.

Narrative: WE WERE CLRED DIRECT ORD DSNDING TO 7000 FT. I WAS THE PNF AND THE FO WAS THE PF. THE FO DISENGAGED THE ACFT AND SELECTED VS ON THE FCU HIMSELF. ATC GAVE US A TURN TO THE DOWNWIND AND, WHILE I WAS SEQUENCING THE FMC FOR THE APCH, THE FO SELECTED OPEN DES ON THE FCU (NON SOP). I BELIEVE HE INADVERTENTLY CHANGED THE ALT TO 6000 FT AND NEITHER ONE OF US NOTICED THE ALT CHANGE. I WAS DISTRACTED WITH THE FMC AND HE WAS DISTRACTED BY HAND FLYING WHILE CHANGING THE FCU. GOING THRU 6700 FT ATC ASKED ABOUT OUR CLRED ALT. AT THE SAME TIME WE HAD A TCASII TFC ALERT FOR AN ACFT 1600 FT BELOW. I STATED WE WERE CLRED TO 6000 FT AND ATC STATED WE WERE CLRED TO 7000 FT BUT CONTINUE TO 6000 FT. I SHOULD HAVE EMPHASIZED TO THE FO TO CALL FOR FCU CHANGES WHILE HAND FLYING PER SOP. NO LOSS OF SEPARATION OCCURRED. IT ONLY SPENT ABOUT 7-8 SECONDS TO SEQUENCE THE FMC FOR THE APCH AND IN THAT SHORT TIME THE ERROR OCCURRED. I'VE BEEN A CAPT ON THE A320 FOR ALMOST 7 YEARS AND THIS IS THE FIRST TIME AN ERROR LIKE THIS OCCURRED. I ALSO THINK A BETTER DESIGN FOR THE FCU WOULD BE TO HAVE A SEPARATE SWITCH FROM THE ALT SELECTOR TO CHANGE DSCNT MODES (LIKE FLT CREWH ON THE 767.)

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.