Narrative:

Curing climb out from sna musel 5 departure, we were given a heading of 200 degrees to intercept a radial (cannot remember which one exactly) off the santa catalina VOR (sxc 111.4) and proceed inbound to the VOR. The flight guidance panel wa engaged and in heading select 200 degrees and the sxc radial and VOR were armed for capture. The FGS captured the radial and the aircraft started to turn right to intercept. After passing through 300 degree heading it became apparent that the turn was not correct and that somehow the intercept was a false one. At this time the FGS was disengaged and a turn back to the left and the original 200 degree heading was commenced. At this time departure called and requested us to continue to turn to heading 180 degrees and stated that we should have still been on a 200 degree heading. We acknowledged that 200 degrees was the assigned heading given. The VOR signal from santa catalina (sxc 111.4) was strong and idented. The radial was inserted in the FGS and armed and the intercept appeared to be normal. Looking back it was not a bit early, but we didn't catch that until well into the turn (approximately 300 degree heading) and the desired radial was still well off to the left on the displays. I don't know why we got a false intercept signal and the FGS went into capture mode, but I felt it was worth mentioning so as to alert other pilots of the potential danger. It impressed upon me to double-check the FGS in all phases of operation.

Google
 

Original NASA ASRS Text

Title: AUTOPLT ON ACR MLG DEPARTING SNA TRIES TO CAPTURE SXC RADIAL ON SID, BUT OVERSHOOTS TURN FOR UNKNOWN REASON.

Narrative: CURING CLBOUT FROM SNA MUSEL 5 DEP, WE WERE GIVEN A HDG OF 200 DEGS TO INTERCEPT A RADIAL (CANNOT REMEMBER WHICH ONE EXACTLY) OFF THE SANTA CATALINA VOR (SXC 111.4) AND PROCEED INBND TO THE VOR. THE FLT GUIDANCE PANEL WA ENGAGED AND IN HDG SELECT 200 DEGS AND THE SXC RADIAL AND VOR WERE ARMED FOR CAPTURE. THE FGS CAPTURED THE RADIAL AND THE ACFT STARTED TO TURN RIGHT TO INTERCEPT. AFTER PASSING THROUGH 300 DEG HDG IT BECAME APPARENT THAT THE TURN WAS NOT CORRECT AND THAT SOMEHOW THE INTERCEPT WAS A FALSE ONE. AT THIS TIME THE FGS WAS DISENGAGED AND A TURN BACK TO THE LEFT AND THE ORIGINAL 200 DEG HDG WAS COMMENCED. AT THIS TIME DEP CALLED AND REQUESTED US TO CONTINUE TO TURN TO HDG 180 DEGS AND STATED THAT WE SHOULD HAVE STILL BEEN ON A 200 DEG HDG. WE ACKNOWLEDGED THAT 200 DEGS WAS THE ASSIGNED HDG GIVEN. THE VOR SIGNAL FROM SANTA CATALINA (SXC 111.4) WAS STRONG AND IDENTED. THE RADIAL WAS INSERTED IN THE FGS AND ARMED AND THE INTERCEPT APPEARED TO BE NORMAL. LOOKING BACK IT WAS NOT A BIT EARLY, BUT WE DIDN'T CATCH THAT UNTIL WELL INTO THE TURN (APPROX 300 DEG HDG) AND THE DESIRED RADIAL WAS STILL WELL OFF TO THE LEFT ON THE DISPLAYS. I DON'T KNOW WHY WE GOT A FALSE INTERCEPT SIGNAL AND THE FGS WENT INTO CAPTURE MODE, BUT I FELT IT WAS WORTH MENTIONING SO AS TO ALERT OTHER PLTS OF THE POTENTIAL DANGER. IT IMPRESSED UPON ME TO DOUBLE-CHK THE FGS IN ALL PHASES OF OPERATION.

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.