A300 flight crew laments the ability of the FMS to comply with RNAV arrival procedures.

Attributes
ACN	1035282
Time
Date	201209
Local Time Of Day	0601-1200
Place
Locale Reference	MEM.Airport
State Reference	TN
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	A300
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	STAR LTOWN 6
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Speed All Types

Narrative:

Flying ltown 6 into memphis; aircraft was not going to make speed restriction at clark. We added more drag via spoilers at which time the nose abruptly pitched down (at 8;400 ft approximately). Selected altitude hold on fcp. Aircraft would not level off so pilot flying (first officer) disengaged autopilot and hand flew aircraft back to 8;000 ft. Note we went approximately 275 ft low. It needs to be noted that the A300 FMS is incapable of flying these stars with any consistency. When it appears they may stay on profile they will always surprise you at the last second with some new exotic maneuver. Quite frankly; I'm tired of being set up for failure with procedures that are developed by someone who doesn't know anything about flying. Release the A300 from the requirement for flying these arrivals. Workload is increased exponentially and safety is reduced in kind.

Original NASA ASRS Text

Title: A300 flight crew laments the ability of the FMS to comply with RNAV arrival procedures.

Narrative: Flying LTOWN 6 into Memphis; aircraft was not going to make speed restriction at CLARK. We added more drag via spoilers at which time the nose abruptly pitched down (at 8;400 FT approximately). Selected ALT Hold on FCP. Aircraft would not level off so pilot flying (First Officer) disengaged autopilot and hand flew aircraft back to 8;000 FT. Note we went approximately 275 FT low. It needs to be noted that the A300 FMS is incapable of flying these STARS with any consistency. When it appears they may stay on profile they will always surprise you at the last second with some new exotic maneuver. Quite frankly; I'm tired of being set up for failure with procedures that are developed by someone who doesn't know anything about flying. Release the A300 from the requirement for flying these arrivals. Workload is increased exponentially and safety is reduced in kind.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.