Narrative:

We were cleared to descend via the eldee 5. Per our procedure we are to set the bottom altitude of the arrival in the altitude window (8;000 ft) when flying in 'VNAV path mode.' the aircraft was on target until the controller issued 2 speed reductions prior to druzz. We asked for and received relief at druzz. The wind at altitude was roughly 280/80. During the second speed reduction the aircraft dropped out of VNAV path. Simultaneously we had a pack trip off line. The first officer began the QRH checklist while I continued with the descent; hustling down to at least be close to the crossing altitude at druzz it did not occur to me that there existed a level portion on the descent between druzz and revue until it was too late and we descended below 15;000 MSL. Experience with new automation and accepting the lowest form of automation when a problem exists may be the key to preventing such events. Once the aircraft dropped out of VNAV path I should have immediately selected the next stepdown altitude (15;000 ft) in the altitude window. Being relatively new on the aircraft I am anxious to master its many modes of descent. Choosing the simplest mode when under duress is usually the safest course of action.

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Original NASA ASRS Text

Title: When their FMC VNAV Path function was unable to comply with both the ELDEE STAR crossing restrictions and ATC speed restrictions the flight crew of a B737NG attempted to manually comply with the crossing at POOCH at 11;000 FT; but while doing so; descended through the required 15;000 FT between DRUZZ and REVUE. Distraction from a tripped pack during the descent was a contributing factor.

Narrative: We were cleared to descend via the ELDEE 5. Per our procedure we are to set the bottom altitude of the arrival in the altitude window (8;000 FT) when flying in 'VNAV Path Mode.' The aircraft was on target until the Controller issued 2 speed reductions prior to DRUZZ. We asked for and received relief at DRUZZ. The wind at altitude was roughly 280/80. During the second speed reduction the aircraft dropped out of VNAV Path. Simultaneously we had a pack trip off line. The First Officer began the QRH checklist while I continued with the descent; hustling down to at least be close to the crossing altitude at DRUZZ it did not occur to me that there existed a level portion on the descent between DRUZZ and REVUE until it was too late and we descended below 15;000 MSL. Experience with new automation and accepting the lowest form of automation when a problem exists may be the key to preventing such events. Once the aircraft dropped out of VNAV Path I should have immediately selected the next stepdown altitude (15;000 FT) in the altitude window. Being relatively new on the aircraft I am anxious to master its many modes of descent. Choosing the simplest mode when under duress is usually the safest course of action.

Data retrieved from NASA's ASRS site as of July 2013 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.