A320
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 110; Flight Crew Total 4571; Flight Crew Type 4571
Confusion; Human-Machine Interface
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors
We were just outside the MNARK waypoint descending via the TBARR1 into Denver when I requested an unrestricted descent in order to expedite down through some turbulence. ATC granted my request and cleared us to descend and maintain 14;000 FT. I took the aircraft out of the managed descent mode and used open descent to descend to 14;000 FT. ATC subsequently amended our clearance as follows; cross BDIVN at or above 14;000 FT then descend via the TBARR1. The next waypoint after BDIVN is KUSHH which has an altitude restriction of 14;000 FT. The Pilot Monitoring (PM) put 13;000 in the FCU as the bottom of the TBARR1 is 13;000 FT at LDORA which is the next waypoint after KUSHH. I acknowledged the change to the altitude in the FCU but failed to put the aircraft back into a managed descent. We were between BDIVN and KUSHH when Denver Center switched us over to approach. As the PM checked in with approach I was expecting the aircraft to level off at 14;000 FT in order to meet the restriction by KUSHH. Just as the aircraft approached 14;000 FT two things happened simultaneously. One; I realized the aircraft wasn't leveling off as I expected; and two; approach cleared us to descend to 10;000 FT and turn left to a heading of 040. I don't believe there was an altitude deviation but I was certainly very fortunate that approach gave us a lower altitude when they did.
On TBARR1 arrival asked for expedited decent to 14;000 feet to get out of moderate turbulence. I put 14;000 feet in altitude window; captain started open descent. Next ATC transmission was a decent via following BDIVN intersection. I put 13;000 in altitude window. Approaching KUSHH intersection captain realized plane was not going to capture altitude to cross KUSHH at 14;000 feet. Managed descent was not selected. At same time got ATC frequency change and new instructions heading 020 descent to 10;000. I don't think we went below 14;000 feet; but would have if not given new ATC instructions while in an open descent Mode.
A320 flight crew reported failing to engage the correct descent mode upon receiving arrival clearance.