A300 flight crew describes the large lead that the FMGC uses to make a 90 degree turn at high altitu...

Attributes
ACN	1115097
Time
Date	201309
Local Time Of Day	1801-2400
Place
Locale Reference	ZDV.ARTCC
State Reference	CO
Environment
Flight Conditions	Marginal
Aircraft 1
Make Model Name	A300
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

Narrative:

On diversion from ZZZ to cos we were given direct flood intersection then fsher join DEBERRY2 arrival. We were inbound from the north to flood; which required a greater than 90 degree turn at that point. In navigation; the aircraft began a turn inside flood to join the selected course. Shortly after we were contacted by denver center that we were assigned the DEBRRY2 and missed flood by 9 miles. The plane was verified to be in navigation and operating as selected. This is the second time in a month ATC has asked about the airbus navigation system. A few weeks back a controller asked why we missed glade springs by 4.7 miles going into gso. He said his separation is 5 miles and the airbus logic compromises that. No conflict was reported in either case; but it seems just a matter of time before one is. Airbus navigation logic.

Original NASA ASRS Text

Title: A300 flight crew describes the large lead that the FMGC uses to make a 90 degree turn at high altitude. This was not acceptable to the Controller involved who questioned the crew as to why it happened.

Narrative: On diversion from ZZZ to COS we were given direct FLOOD Intersection then FSHER join DEBERRY2 arrival. We were inbound from the north to FLOOD; which required a greater than 90 degree turn at that point. In NAV; the aircraft began a turn inside FLOOD to join the selected course. Shortly after we were contacted by Denver Center that we were assigned the DEBRRY2 and missed FLOOD by 9 miles. The plane was verified to be in NAV and operating as selected. This is the second time in a month ATC has asked about the Airbus NAV system. A few weeks back a Controller asked why we missed Glade Springs by 4.7 miles going into GSO. He said his separation is 5 miles and the Airbus logic compromises that. No conflict was reported in either case; but it seems just a matter of time before one is. Airbus NAV logic.

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.

A300 flight crew describes the large lead that the FMGC uses to make a 90 degree turn at high altitude. This was not acceptable to the controller involved who questioned the crew as to why it happened.