Narrative:

On departure from fll, we were assigned a heading of 090 degrees for vectors to the thndr transition. Subsequently, we were assigned a heading of 300 degrees to intercept the transition . The first officer (PF) engaged the navigation mode and an intercept point was displayed on the navigation display. We intercepted the 335 degree radial of the dhp VOR. At this point, ATC advised us that we needed to turn left to 280 degrees because we had intercepted the arkes transition. The first officer immediately turned off the autoplt and executed a manual hard left turn back to a 280 degree heading. At this point, we realized that our navigation displays were off significantly so reverted to VOR navigation and intercepted the real 335 degree radial of the dhp VOR. What is so disturbing about this incident is that we received no warning of any type that we had a navigation error. After about 10 mins of flight and well after the initial erroneous navigation error, we finally did receive FMGC message to check aircraft position. This was the first warning we received that there was a problem. Once we finally established ourselves on the departure using VOR navigation and were above about 12000 ft, we were able to determine that the FMGC's were not receiving radio updating. The navigation error was at this point approximately 9 NM. This is a rather large error for a tripe IRS equipped aircraft so shortly after takeoff. We contacted ATC and soc and changed our equipment status to '/a' for the remainder of the flight. Moc was advised of our problem but offered no solution. I entered this discrepancy into the aircraft logbook. As far as I now there was no loss of separation. Unfortunately, I still do not have any idea what caused this error.

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Original NASA ASRS Text

Title: A320 FLT CREW DEPARTS FLL AND FLIES THE WRONG DEP.

Narrative: ON DEP FROM FLL, WE WERE ASSIGNED A HDG OF 090 DEGS FOR VECTORS TO THE THNDR TRANSITION. SUBSEQUENTLY, WE WERE ASSIGNED A HDG OF 300 DEGS TO INTERCEPT THE TRANSITION . THE FO (PF) ENGAGED THE NAV MODE AND AN INTERCEPT POINT WAS DISPLAYED ON THE NAV DISPLAY. WE INTERCEPTED THE 335 DEG RADIAL OF THE DHP VOR. AT THIS POINT, ATC ADVISED US THAT WE NEEDED TO TURN L TO 280 DEGS BECAUSE WE HAD INTERCEPTED THE ARKES TRANSITION. THE FO IMMEDIATELY TURNED OFF THE AUTOPLT AND EXECUTED A MANUAL HARD L TURN BACK TO A 280 DEG HDG. AT THIS POINT, WE REALIZED THAT OUR NAV DISPLAYS WERE OFF SIGNIFICANTLY SO REVERTED TO VOR NAV AND INTERCEPTED THE REAL 335 DEG RADIAL OF THE DHP VOR. WHAT IS SO DISTURBING ABOUT THIS INCIDENT IS THAT WE RECEIVED NO WARNING OF ANY TYPE THAT WE HAD A NAV ERROR. AFTER ABOUT 10 MINS OF FLT AND WELL AFTER THE INITIAL ERRONEOUS NAV ERROR, WE FINALLY DID RECEIVE FMGC MESSAGE TO CHK ACFT POS. THIS WAS THE FIRST WARNING WE RECEIVED THAT THERE WAS A PROB. ONCE WE FINALLY ESTABLISHED OURSELVES ON THE DEP USING VOR NAV AND WERE ABOVE ABOUT 12000 FT, WE WERE ABLE TO DETERMINE THAT THE FMGC'S WERE NOT RECEIVING RADIO UPDATING. THE NAV ERROR WAS AT THIS POINT APPROX 9 NM. THIS IS A RATHER LARGE ERROR FOR A TRIPE IRS EQUIPPED ACFT SO SHORTLY AFTER TKOF. WE CONTACTED ATC AND SOC AND CHANGED OUR EQUIP STATUS TO '/A' FOR THE REMAINDER OF THE FLT. MOC WAS ADVISED OF OUR PROB BUT OFFERED NO SOLUTION. I ENTERED THIS DISCREPANCY INTO THE ACFT LOGBOOK. AS FAR AS I NOW THERE WAS NO LOSS OF SEPARATION. UNFORTUNATELY, I STILL DO NOT HAVE ANY IDEA WHAT CAUSED THIS ERROR.

Data retrieved from NASA's ASRS site as of July 2007 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.