Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 60; Flight Crew Total 15000; Flight Crew Type 5000
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Aircraft; Procedure
On climbout from LAS on the COWBY5 I coupled Auto Pilot at 1200 FT AGL and on the way from FIXIX to ROPPR we were given direct CEASR and resume SID; about 5 miles prior to CEASR the line being drawn on the NAV display seemed like it was going to turn early but with about a 120 degree left turn I thought it could be acceptable.  It started to turn at 3 miles prior and almost immediately ATC questioned where we were going.  I disconnected NAV and went to heading mode and turned back toward CEASR. This happened to me 4 months ago (Report filed) and as in this case we did not receive any indication from the FMS of being off course; which leads me to believe that the flight director believed it was on course.  In my opinion this aircraft should not be used on RNAV departures without an overhaul to the software.
A300 Captain departing LAS is given a shortcut to CEASR on the COWBY5 which required a 120 degree heading change over CEASR. The FMGC leads this turn by three miles causing ATC to question the crew as to where they are going.