A320 flight crew has altitude excursion during approach to atl.

Attributes
ACN	564095
Time
Date	200210
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : depot
State Reference	GA
Altitude	msl bound lower : 4000 msl bound upper : 4300
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : a80.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 27l other
Flight Phase	descent : approach descent : holding
Route In Use	approach : instrument precision arrival : holding pattern
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 12000 flight time type : 2183
ASRS Report	564095
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure
Independent Detector	other flight crewa other flight crewb
Resolutory Action	aircraft : automation overrode flight crew flight crew : overrode automation flight crew : overcame equipment problem flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATC cleared us to fly 230 degrees, intercept and descend to 4000 ft for the ILS runway 27L, 7 mi from depot. We had altitude capture at 4000 ft, localizer armed. The approach mode was armed before localizer capture and we got an uncommanded pitch up from the autoplt. We gained 300 ft before the autoplt was disconnected and the problem corrected for a normal approach. This characteristic anomaly is in the A320 bulletins and we armed the approach too early. The rest of the approach was perfectly flown and was absolutely normal for a low visibility heavy rain approach in CAT I conditions. Human factors: no calls were missed, all corrective action was taken in a timely manner, no traffic conflict existed, no call from ATC. The problem was limited to very full bladders since we had not anticipated holding at altitudes below sterile cockpit altitude, with the flight attendants seated for the hold, approach. Basically, with the current security procedures, we were in a jeopardy situation, since full bladders or not, we couldn't leave the cockpit. Both pilots were uncomfortable, but able to fly and respond to input. This little airbus nuance escaped our attention because of the strong desire to complete a safe, stabilized approach and get our jet on the ground safely. We were about 15 mins from diverting.

Original NASA ASRS Text

Title: A320 FLC HAS ALT EXCURSION DURING APCH TO ATL.

Narrative: ATC CLRED US TO FLY 230 DEGS, INTERCEPT AND DSND TO 4000 FT FOR THE ILS RWY 27L, 7 MI FROM DEPOT. WE HAD ALT CAPTURE AT 4000 FT, LOC ARMED. THE APCH MODE WAS ARMED BEFORE LOC CAPTURE AND WE GOT AN UNCOMMANDED PITCH UP FROM THE AUTOPLT. WE GAINED 300 FT BEFORE THE AUTOPLT WAS DISCONNECTED AND THE PROB CORRECTED FOR A NORMAL APCH. THIS CHARACTERISTIC ANOMALY IS IN THE A320 BULLETINS AND WE ARMED THE APCH TOO EARLY. THE REST OF THE APCH WAS PERFECTLY FLOWN AND WAS ABSOLUTELY NORMAL FOR A LOW VISIBILITY HVY RAIN APCH IN CAT I CONDITIONS. HUMAN FACTORS: NO CALLS WERE MISSED, ALL CORRECTIVE ACTION WAS TAKEN IN A TIMELY MANNER, NO TFC CONFLICT EXISTED, NO CALL FROM ATC. THE PROB WAS LIMITED TO VERY FULL BLADDERS SINCE WE HAD NOT ANTICIPATED HOLDING AT ALTS BELOW STERILE COCKPIT ALT, WITH THE FLT ATTENDANTS SEATED FOR THE HOLD, APCH. BASICALLY, WITH THE CURRENT SECURITY PROCS, WE WERE IN A JEOPARDY SIT, SINCE FULL BLADDERS OR NOT, WE COULDN'T LEAVE THE COCKPIT. BOTH PLTS WERE UNCOMFORTABLE, BUT ABLE TO FLY AND RESPOND TO INPUT. THIS LITTLE AIRBUS NUANCE ESCAPED OUR ATTN BECAUSE OF THE STRONG DESIRE TO COMPLETE A SAFE, STABILIZED APCH AND GET OUR JET ON THE GND SAFELY. WE WERE ABOUT 15 MINS FROM DIVERTING.

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.