Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Aircraft; Procedure
Captain was pilot flying and was cleared to 'descend via the Korry 3 arrival' into LGA. All crossing restrictions were programmed in the MCDU and verified. Captain had planned for a high speed descent as there was no speed restrictions assigned. During descent; ATC adjusted our clearance to include '270 KTS at BRAND.' Speed brakes were extended to help meet this assignment and aircraft was in managed speed and managed descent. The aircraft was programmed to cross DAVYS at or above 13;000 FT and the MCDU indicated that this restriction would be met. At approximately 13;300 FT I noticed that with the current descent rate; it did not appear that the level off would occur by 13;000 FT at DAVYS. The vertical speed level-off button was pushed and even then; the descent rate was such that the aircraft was going to descend below 13;000 FT 2-3 miles prior to DAVYS. Just below 13;000 FT; the Captain disengaged the autopilot and leveled off around 12;200 FT followed by a return to 13;000 FT and then the KORRY 3 arrival without further complications. There was no alert or indication by ATC that a crossing restriction had not been met. It appears that on the A320 aircraft specifically; using speed brakes at higher speeds on descent will induce descent rates that will not be able to be overcome to meet some crossing restrictions while using the autopilot. In this circumstance; the A319 aircraft probably would not have had a problem; and this event serves to remind that the A320 aircraft are slower to respond while on autopilot to changes in pitch. In any regard; when ATC changes an airspeed clearance on an arrival; in the descent; to something less manageable; it may be prudent to say 'unable' next time.
During a high speed descent on the LGA KORRY 3 arrival; ATC issued a 270 KTS BRAND constraint which caused an A320 to go below the DAVYS 13;000 FT constraint by 750 FT.