Narrative:

Lax center cleared us direct at 14000', then maintain 13000'. I read back the clearance and set 14000', into the altitude alert window. I told the captain that I would be off the #2 communication radio while getting the ATIS and calling operations in ont. While I was off, I heard the altitude horn and called '15 for 14' and then went back to the ATIS. I never heard another alert. Because of poor reception, I had to listen to the ATIS 3 times. I felt an abrupt pull up and the captain pushed the throttles up very rapidly and said 'how did we get down here?' I looked at the altimeter and saw that we were at 12200'. We immediately climbed back to 13000'. Atl never commented and is probably not aware of the excursion. A high cockpit workload during descent was just enough of a distraction to cause the 800' excursion. The captain was flying the aircraft, talking to ATC, trying to comply with a crossing restriction and tuning his own navigation radios. I was off the #2 radio, copying the ATIS and tuning my own radios in addition to doing the checklist. Another problem is requiring pilots to fly 2 very drastically different aircraft types. The medium large transport type a and medium large transport type B although legally the same aircraft are as different as day and night. Our first 4 legs were in a type B that will capture the selected altitude after alerting you. Our last leg (this one) was in a type a that will not capture the altitude after alerting you. The distraction of the workload and the different aircraft type were both contributing factors. Under the circumstances, the captain did a fine job of correcting the problem. The situation could have been much worse. Supplemental information from acn 139300. First officer communicating to company on radio #1. Captain guarding ATC communication on #2 and hand flying aircraft.

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Original NASA ASRS Text

Title: ACR-MLG ALT DEVIATE OVERSHOT DURING DESCENT INTO ONT.

Narrative: LAX CENTER CLRED US DIRECT AT 14000', THEN MAINTAIN 13000'. I READ BACK THE CLRNC AND SET 14000', INTO THE ALT ALERT WINDOW. I TOLD THE CAPT THAT I WOULD BE OFF THE #2 COM RADIO WHILE GETTING THE ATIS AND CALLING OPS IN ONT. WHILE I WAS OFF, I HEARD THE ALT HORN AND CALLED '15 FOR 14' AND THEN WENT BACK TO THE ATIS. I NEVER HEARD ANOTHER ALERT. BECAUSE OF POOR RECEPTION, I HAD TO LISTEN TO THE ATIS 3 TIMES. I FELT AN ABRUPT PULL UP AND THE CAPT PUSHED THE THROTTLES UP VERY RAPIDLY AND SAID 'HOW DID WE GET DOWN HERE?' I LOOKED AT THE ALTIMETER AND SAW THAT WE WERE AT 12200'. WE IMMEDIATELY CLBED BACK TO 13000'. ATL NEVER COMMENTED AND IS PROBABLY NOT AWARE OF THE EXCURSION. A HIGH COCKPIT WORKLOAD DURING DSCNT WAS JUST ENOUGH OF A DISTR TO CAUSE THE 800' EXCURSION. THE CAPT WAS FLYING THE ACFT, TALKING TO ATC, TRYING TO COMPLY WITH A XING RESTRICTION AND TUNING HIS OWN NAV RADIOS. I WAS OFF THE #2 RADIO, COPYING THE ATIS AND TUNING MY OWN RADIOS IN ADDITION TO DOING THE CHKLIST. ANOTHER PROB IS REQUIRING PLTS TO FLY 2 VERY DRASTICALLY DIFFERENT ACFT TYPES. THE MLG TYPE A AND MLG TYPE B ALTHOUGH LEGALLY THE SAME ACFT ARE AS DIFFERENT AS DAY AND NIGHT. OUR FIRST 4 LEGS WERE IN A TYPE B THAT WILL CAPTURE THE SELECTED ALT AFTER ALERTING YOU. OUR LAST LEG (THIS ONE) WAS IN A TYPE A THAT WILL NOT CAPTURE THE ALT AFTER ALERTING YOU. THE DISTR OF THE WORKLOAD AND THE DIFFERENT ACFT TYPE WERE BOTH CONTRIBUTING FACTORS. UNDER THE CIRCUMSTANCES, THE CAPT DID A FINE JOB OF CORRECTING THE PROB. THE SITUATION COULD HAVE BEEN MUCH WORSE. SUPPLEMENTAL INFO FROM ACN 139300. F/O COMMUNICATING TO COMPANY ON RADIO #1. CAPT GUARDING ATC COM ON #2 AND HAND FLYING ACFT.

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.