A320
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 200; Flight Crew Total 24000; Flight Crew Type 8000
Human-Machine Interface
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Human Factors
Setting the lowest published altitude on an arrival/approach makes for a very nice descent when all is going well.  ATC provided many speed assignments to 'keep our speed up.'  While transitioning from a managed descent to the approach mode; we briefly failed to observe the subtle changes to the FMA's that indicated a mode reversion to our VNAV profile.  It would be helpful to have a more noticeable and audible alert when a reversion occurs.
Approaching FUELR on approach into LAX having transitioned to 25L approach from River 2 arrival; crew did not recognize in a timely fashion a reversion from managed descent mode. Pilot Monitoring alerted Pilot Flying descending through restriction but with rate of descent final level off occurred 500 feet below 7;000+ restriction. Managed descent was re-engaged and next restriction; 6;000+ was made.
A320 flight crew reports descending below the FUELR crossing restriction on the ILS 25L approach to LAX when the aircraft transitions to approach mode from LNAV/VNAV without the crew noticing. The crew detects the error and the remainder of the restrictions are met.