A300
Flight Crew Air Transport Pilot (ATP)
Distraction; Human-Machine Interface
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft; Chart Or Publication; Procedure
As we approached ARG; we were cleared to descend via the FNCHR1 RNAV STAR. All altitude and airspeed constraints were previously reviewed and confirmed by the crew during the approach briefing. The only modifications to the [line selected] FMS procedure were to change the Cost Index to 132 just prior to top of descent; and the deletion of the 'vector leg' after JAYWA in order to provide a more accurate Fuel Prediction figure for landing. The arrival was flown in Profile with the Altitude Select window set and confirmed for 4;000 FT (The lowest altitude on FNCHR1 arrival at JAYWA). All altitude and airspeed constraints were satisfied for all points from start of arrival through crossing LOONR waypoint. After crossing LOONR at 9;000 and 210 KTS; aircraft continued descent in Profile for the 'at or above' 8;000 crossing restriction at BOWEN. Passing through approximately 8;700 FT; the aircraft pitched over with rapidly increasing airspeed; though target airspeed still displayed 210 KTS and crossing restriction at BOWEN still showed 8;000 on the FMS and the constraints display. I initially attempted to control the airspeed increase with speed brakes; but it became apparent that further action would be required to correct the deviation. I then disconnected the autopilot to arrest the descent and increasing airspeed. We crossed BOWEN at approximately 7;700 and 240 KTS. We stopped the descent at 7;500 FT and slowed to 210 KTS before continuing the descent via the FNCHR1 arrival during which Approach cleared us to stop our descent at 6;000. The remainder of arrival and approach proceeded normally.I believe I need to take more aggressive action to arrest deviations on profile descents. Also; after observing and hearing the number of constraint deviations that are occurring with Airbus RNAV arrivals that are flown in Profile; I recommend Airbus arrivals be flown in LVL/CH.
After LOONR Intersection; the aircraft began a programmed descent to 4;000 at 210 KTS. Sink rate was appropriate at 1;000 FPM to cross at/or above 8;000 FT at BOWEN.Other Airbus pilots have reported the same problem on this STAR.
An A300 flight crew descending via the FNCHR RNAV STAR to MEM was surprised when the FMS inexplicably increased their rate of descent and airspeed and crossed BOWEN 300 FT low and 30 KIAS fast. They disconnected autoflight and returned to their clearance. The analyst is not a champion of attempting to manually manage crossing restrictions on Optimized RNAV STARs as doing so often requires excessive flight crew workload; often at the expense of other high priority tasks. Vertical Navigation autoflight functions should be capable of complying with the demands of a complex vertical flight path and if failures to do so occur with any degree of frequency either the STAR or the aircraft should be examined for compatibility problems.