Flight Crew Air Transport Pilot (ATP)
Workload; Situational Awareness; Human-Machine Interface; Distraction; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Aircraft; Procedure
In cruise at FL320 we were assigned a descend via IVANE5; except maintain 250. I input 250kts in the descent page; deleted all speed restrictions above 250kts; CAMI'd and ensured managed speed was engaged. We had previously verified the entire arrival procedure; including all altitude restrictions and airspeeds. Upon receiving the clearance I selected managed descent; and again verified managed speed was selected. The aircraft began down; with a bracket speed around 250kts. The FMC respected the first altitude restriction of FL270 at MSTRD; upon crossing MSTRD we noticed that the aircraft was accelerating rapidly in the descent; while initially maintaining over 50% N1. We were discussing this; and observed the power levelers approach idle. We were slightly above (one dot) our descent profile. We then noticed that we had descended below the 240-260 window at MAYOS. We were approaching FL220 and would have continued a rapid descent below 220 well prior to KIYEN. We verified that Managed Speed; LNAV; and Managed Descent were all engaged. We were still indicating above profile; and well over our managed speed target. We disabled the automation; and manually captured FL220 to prevent further deviation. The Captain informed ATC that we were discontinuing the IVANE arrival; and the flight continued normally. We CAMI'd the IVANE5; as well as the speed changes. We discussed the top of descent; and anticipated a normal approach. We are not sure what caused this FMS anomaly. Ultimately; the concern over the airspeed deviation caused both of us to focus on that; allowing us to miss the further anomalies. The aircraft often has issues when an optimal profile descent (OPD) is manipulated outside of the database parameters and requires diligence. This [has] become a 'standard' practice for ATC. Deviations from established OPD procedures should be kept to a minimum.
[Report narrative contained no additional information.]
An Airbus A320 series flight crew reported descending on the CLT IVANE 5 RNAV they were assigned a 250 kt restriction. While in managed speed; the FMC ignored the MAYOS altitude constraint and projected missing the KIYEN altitude constraint. The aircraft had difficulty flying a modified RNAV optimal profile descent.