A320 crew leaves altitude on STAR before they are cleared.

Attributes
ACN	452621
Time
Date	199910
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : pdz.vor
State Reference	CA
Altitude	msl bound lower : 16500 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sct.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : pdz 3
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : cfi pilot : atp
Experience	flight time last 90 days : 120 flight time total : 9000 flight time type : 150
ASRS Report	452621
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : atp
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 250
ASRS Report	452891
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure 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	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We had been cleared the pdz 3 arrival runway 25L into lax and told to cross konzl at 17000 ft. We leveled at 17000 ft prior to konzl and were both expecting our next clearance to be 'descend on the pdz 3 arrival.' at just past konzl, the controller told us 'you are now cleared the pdz 3 arrival to runway 24R.' I was the PNF and acknowledged the clearance. I went 'heads down' and activated the secondary flight plan. When I completed that task, I looked up and immediately noticed the altitude select window indicated '8000 ft.' I glanced at the altimeter and we were in a descent passing 16700 ft. I informed him we were not cleared to descend and to immediately climb back to 17000 ft. Our lowest altitude was 16500 ft. Level at 17000 ft, I asked approach for a descent clearance and received a clearance. To 14000 ft with no comment about our altitude deviation. We were in an 'anticipation' mode getting high on the profile and expecting a clearance. When the first officer heard the clearance he reacted on what he expected. 2 company procedure violations, not confirming with PNF new altitude and setting the lowest stepdown fix not the next. My 'seat-of-the-pants' did not detect the descent when I was heads down.

Original NASA ASRS Text

Title: A320 CREW LEAVES ALT ON STAR BEFORE THEY ARE CLRED.

Narrative: WE HAD BEEN CLRED THE PDZ 3 ARR RWY 25L INTO LAX AND TOLD TO CROSS KONZL AT 17000 FT. WE LEVELED AT 17000 FT PRIOR TO KONZL AND WERE BOTH EXPECTING OUR NEXT CLRNC TO BE 'DSND ON THE PDZ 3 ARR.' AT JUST PAST KONZL, THE CTLR TOLD US 'YOU ARE NOW CLRED THE PDZ 3 ARR TO RWY 24R.' I WAS THE PNF AND ACKNOWLEDGED THE CLRNC. I WENT 'HEADS DOWN' AND ACTIVATED THE SECONDARY FLT PLAN. WHEN I COMPLETED THAT TASK, I LOOKED UP AND IMMEDIATELY NOTICED THE ALT SELECT WINDOW INDICATED '8000 FT.' I GLANCED AT THE ALTIMETER AND WE WERE IN A DSCNT PASSING 16700 FT. I INFORMED HIM WE WERE NOT CLRED TO DSND AND TO IMMEDIATELY CLB BACK TO 17000 FT. OUR LOWEST ALT WAS 16500 FT. LEVEL AT 17000 FT, I ASKED APCH FOR A DSCNT CLRNC AND RECEIVED A CLRNC. TO 14000 FT WITH NO COMMENT ABOUT OUR ALTDEV. WE WERE IN AN 'ANTICIPATION' MODE GETTING HIGH ON THE PROFILE AND EXPECTING A CLRNC. WHEN THE FO HEARD THE CLRNC HE REACTED ON WHAT HE EXPECTED. 2 COMPANY PROC VIOLATIONS, NOT CONFIRMING WITH PNF NEW ALT AND SETTING THE LOWEST STEPDOWN FIX NOT THE NEXT. MY 'SEAT-OF-THE-PANTS' DID NOT DETECT THE DSCNT WHEN I WAS HEADS DOWN.

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.