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B757 flight crew reports runway change by ZLA prior to konzl on the seavu arrival to lax; resulting in an altitude deviation at konzl.

Narrative:

We were on the seavu arrival into lax. ATC cleared us to cross konzl at 17;000 ft. I was using vertical speed because VNAV had been inconsistent earlier during the flight. Approximately 5 NM from konzl; as we were approaching 17;000 ft; but not yet in altitude hold; ATC simultaneously changed our runway assignment and cleared us for the descent via the arrival. I entered the next altitude in the window as the captain reprogrammed the FMS for the new runway. A few seconds later; as we reviewed the new runway information; I realized we were descending through 16;700 ft and still 2.4 NM from konzl. I quickly disengaged the autopilot and corrected to 17;000 ft as we crossed konzl. I believe the altimeter touched 16;600 during my correction. We checked the TCAS and saw no aircraft within 5 NM at any altitude. ATC didn't mention our altitude deviation. My use of vertical speed combined with the altitude change just prior to level off (and therefore prior to altitude cap) allowed vertical speed to briefly fly through our assigned altitude. Nothing new here. Just a reminder of good old fashioned pilot sense. Perhaps we had been missing some entry in the FMS which caused VNAV to work incorrectly. That caused a break in our habit patterns (using vertical speed instead of VNAV); which during a busy moment caused me to lose attention momentarily. In the future; I will make sure one pilot is always watching the plane and making sure it is conforming to the clearances (konzl at 17;000) instead of both of us scrambling to implement multiple changes to our clearance.

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Original NASA ASRS Text

Title: B757 Flight Crew reports runway change by ZLA prior to KONZL on the SEAVU arrival to LAX; resulting in an altitude deviation at KONZL.

Narrative: We were on the SEAVU arrival into LAX. ATC cleared us to cross KONZL at 17;000 FT. I was using vertical speed because VNAV had been inconsistent earlier during the flight. Approximately 5 NM from KONZL; as we were approaching 17;000 FT; but not yet in altitude hold; ATC simultaneously changed our runway assignment and cleared us for the descent via the arrival. I entered the next altitude in the window as the Captain reprogrammed the FMS for the new runway. A few seconds later; as we reviewed the new runway information; I realized we were descending through 16;700 FT and still 2.4 NM from KONZL. I quickly disengaged the autopilot and corrected to 17;000 FT as we crossed KONZL. I believe the altimeter touched 16;600 during my correction. We checked the TCAS and saw no aircraft within 5 NM at any altitude. ATC didn't mention our altitude deviation. My use of vertical speed combined with the altitude change just prior to level off (and therefore prior to ALT CAP) allowed vertical speed to briefly fly through our assigned altitude. Nothing new here. Just a reminder of good old fashioned pilot sense. Perhaps we had been missing some entry in the FMS which caused VNAV to work incorrectly. That caused a break in our habit patterns (using vertical speed instead of VNAV); which during a busy moment caused me to lose attention momentarily. In the future; I will make sure one pilot is always watching the plane and making sure it is conforming to the clearances (KONZL at 17;000) instead of both of us scrambling to implement multiple changes to our clearance.

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.