EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem
Aircraft; Human Factors
Descent to SJC via BRIXX2. Entire descent maintained in magenta 'PTH' FMA mode. Vertical cross track error observed within 25-40 ft. Conditions VMC. Both First Officer and Captain baro altitudes set to 29.96. Perf data was .75/290 speed with 2.8 angle. During descent to 12;000 ft. descending via BRIXX2; OAK handed off (flight) to NORCAL approach. Request was made for RNAV Z 30L. (flight) was cleared join RNAV Z 30L from BRIXX2 arrival common waypoints except maintain 12;000 ft. Captain selected RNAV Z 30L common fixes (with altitude of 7;000 ft. on JILAN and 210/4800A on YADUT) with 'VERIFY' statement followed by 'ACTIVATE' statement from First Officer.Later; (flight) was then cleared to 7;000 ft. after freq hand off. Through descent; then cleared for the RNAV Z 30L off the BRIXX2 STAR. Altitude selector then set to 1;600 ft. for WOXAR while in PTH mode with APP armed (LNAV engaged /GP armed). While in PTH mode received CHECK ALT CONSTRAINT message ~200-300ft below JILNA of 7000ft with JILNA as active flight plan fix. ALT hold selected on guidance panel to prevent further baro altitude deviation by Captain.  Airplane was at baro altitude ~350-440 ft. below 7;000 ft. in ALT mode as the vertical deviations showed airplane high of VNAV path and growing at waypoint sequence constraint.  First Officer selected 210/4800 on YADUT for vertical direct-to on Flight Plan page. FLIGHT PATH ANGLE TOO STEEP message occurred. VNAV was then selected and remaining of RNAV Z 30L constraints followed per procedure. VNAV path computed a FPA not coincidental to 7;000 ft. altitude constraint in active flight plan at JILAN 7;000 ft. constraint on an RNP AR procedure outside the FAF. No discrepancies reported by ATC. Airport was visual so no missed approach conducted. Issues observed may prevent maintaining Ops spec approval of Baro VNAV system for RNP AR C400.
E175 F/O reported the FMC was not performing properly in VNAV and was a factor in their failure to meet charted crossing restrictions on arrival into destination .