B737 captain reports descent below published altitude during transition from seavu fix to the ILS 24...

Narrative:

While flying the seavu 2 arrival to lax; we were planning the 24R approach. We planned; briefed; and loaded the approach into the FMC. Approach gave us the arrival to 25L. We made the necessary changes and briefed and loaded the new approach. Then they changed the arrival back to 24R. We reloaded that approach. During the transition from the arrival to the approach; we crossed seavu fix at 10;000 ft and continued to descend to 9500 ft. We should have maintained 10;000 ft until crossing the next fix which was skoll. The first officer was using the autothrottle and VNAV functions but didn't notice the descent below 10;000 ft as the workload went up during the runway changes. I was the pm but didn't catch the descent until we were below 10;000 ft. Both pilots need to improve their proficiency using VNAV and autothrottle. We both thought it was going to maintain the descent profile. Even though the workload went up; I should ensure the aircraft was doing what we thought it was going to do.

Original NASA ASRS Text

Title: B737 Captain reports descent below published altitude during transition from SEAVU fix to the ILS 24R at LAX. Deviation occurred after the second runway change during the arrival.

Narrative: While flying the SEAVU 2 Arrival to LAX; we were planning the 24R approach. We planned; briefed; and loaded the approach into the FMC. Approach gave us the arrival to 25L. We made the necessary changes and briefed and loaded the new approach. Then they changed the arrival back to 24R. We reloaded that approach. During the transition from the arrival to the approach; we crossed SEAVU fix at 10;000 ft and continued to descend to 9500 ft. We should have maintained 10;000 ft until crossing the next fix which was SKOLL. The First Officer was using the autothrottle and VNAV functions but didn't notice the descent below 10;000 ft as the workload went up during the runway changes. I was the PM but didn't catch the descent until we were below 10;000 ft. Both Pilots need to improve their proficiency using VNAV and autothrottle. We both thought it was going to maintain the descent profile. Even though the workload went up; I should ensure the aircraft was doing what we thought it was going to do.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	853368
Time
Date	200909
Local Time Of Day	1201-1800
Place
Locale Reference	LAX.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR SEAVU
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Experience	Flight Crew Last 90 Days 195
Events
Anomaly	Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

B737 captain reports descent below published altitude during transition from seavu fix to the ILS 24R at lax. Deviation occurred after the second runway change during the arrival.