Narrative:

I flew IFR from the san francisco bay area to smo to attend a business conference. It was the first time I've flown to la in over 5 yrs. The aircraft was new; an experimental. I have limited experience with the GPS; a GX60; especially its approach capability. I programmed in the flight plan to smo; and correctly anticipated the fernando 5 arrival. The flight went reasonably well in VMC until approaching darts intersection. ATC vectored me to the GPS/VOR approach; skipping darts. I enabled the GPS approach; but the GX60 tried to take me to the IAF; away from smo (I realized this later; at the time I saw it wasn't showing me the right distance and direction; but that's all). I tried flying the approach on the MX20's moving map with approach overlay. That got me to the airport; but too high; since I didn't have distance numbers. Smo tower offered me a chance to circle down VFR or execute the missed. Given that the east edge of the airport was VMC; and I could see the runway; I went VFR. Tower sent me out on a long downwind to try to get in following an IFR aircraft. This is where things deteriorated. During my downwind; tower kept calling out the landing traffic; which I couldn't see (visibility was less than 5 miles). I was unfamiliar with the area east of the tower; and with the distraction of looking for traffic; and trying to switch modes to VFR; I didn't maintain altitude; direction; and speed well. ATC called out that I was below 1000 ft and said I was turning in towards the oncoming traffic; which I also corrected. I asked for a vector to fly; but was refused; telling me I was 'on downwind.' I asked for tower to call my base; which after a while; they reluctantly did. Once turning base; the airport was in sight; and the rest of the approach and landing was uneventful. Here's my analysis of the situation -- what went wrong and what should have been different: I didn't know my GPS' approach mode well enough. Later; I used the pc simulator more; figured out what had happened; and learned how to choose an IAF (when available); and how to program for 'vectors to final.' it might have been better to take the missed approach; since I would have stayed in 'IFR mode.' hopefully; I would have kept up enough to try the VOR approach; or take the visual. I should have had the VOR dialed in as backup. I would have had lateral guidance and distance. I should have studied the smo vicinity more carefully on the VFR charts before flying there; so the long downwind wouldn't have been as hard to figure out. I also should have switched to the VFR charts immediately. The pc simulator; and the docs for it and GPS itself are poor. It's very difficult to figure out how to place the simulated aircraft in the right place and configure the simulator to exercise the approach facility. The docs also don't explain the approach functionality well; and are really only clear once you have already figured out how everything works. The GX60 interface is not intuitive. For smo; it lists a set of fixes; but doesn't allow you to pick a different one. The only indication of this is that the dial 'does nothing.' since the font is small; it's hard to notice this. You have to select the full approach; and know that you should then hit the [sel] button to get a choice of 'vectors to the approach' instead. I want to be able to pick any fix; in case I need to switch things around at the last minute. ATC should have let me circle; lose altitude; and land. I was set up for that (basically a circling approach). Instead they sent me away from the airport VFR for an extended period of time; forcing me to navigate in an area I'm unfamiliar with; and near class C and B airspace that I suddenly have to worry about; being VFR. Since they had me on radar; they could have given me a vector to fly to help me out; and been more willing to call my base.

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Original NASA ASRS Text

Title: EXPERIMENTAL AIRCRAFT PILOT CITED INADEQUATE KNOWLEDGE OF THE APPROACH FUNCTIONS OF HIS GPS AS A FACTOR IN ALTITUDE AND TRACK DEVIATIONS IN A HIGH DENSITY TERMINAL AREA.

Narrative: I FLEW IFR FROM THE SAN FRANCISCO BAY AREA TO SMO TO ATTEND A BUSINESS CONFERENCE. IT WAS THE FIRST TIME I'VE FLOWN TO LA IN OVER 5 YRS. THE ACFT WAS NEW; AN EXPERIMENTAL. I HAVE LIMITED EXPERIENCE WITH THE GPS; A GX60; ESPECIALLY ITS APCH CAPABILITY. I PROGRAMMED IN THE FLT PLAN TO SMO; AND CORRECTLY ANTICIPATED THE FERNANDO 5 ARR. THE FLT WENT REASONABLY WELL IN VMC UNTIL APCHING DARTS INTXN. ATC VECTORED ME TO THE GPS/VOR APCH; SKIPPING DARTS. I ENABLED THE GPS APCH; BUT THE GX60 TRIED TO TAKE ME TO THE IAF; AWAY FROM SMO (I REALIZED THIS LATER; AT THE TIME I SAW IT WASN'T SHOWING ME THE RIGHT DISTANCE AND DIRECTION; BUT THAT'S ALL). I TRIED FLYING THE APCH ON THE MX20'S MOVING MAP WITH APCH OVERLAY. THAT GOT ME TO THE ARPT; BUT TOO HIGH; SINCE I DIDN'T HAVE DISTANCE NUMBERS. SMO TWR OFFERED ME A CHANCE TO CIRCLE DOWN VFR OR EXECUTE THE MISSED. GIVEN THAT THE E EDGE OF THE ARPT WAS VMC; AND I COULD SEE THE RWY; I WENT VFR. TWR SENT ME OUT ON A LONG DOWNWIND TO TRY TO GET IN FOLLOWING AN IFR ACFT. THIS IS WHERE THINGS DETERIORATED. DURING MY DOWNWIND; TWR KEPT CALLING OUT THE LNDG TFC; WHICH I COULDN'T SEE (VIS WAS LESS THAN 5 MILES). I WAS UNFAMILIAR WITH THE AREA E OF THE TWR; AND WITH THE DISTRACTION OF LOOKING FOR TFC; AND TRYING TO SWITCH MODES TO VFR; I DIDN'T MAINTAIN ALT; DIRECTION; AND SPD WELL. ATC CALLED OUT THAT I WAS BELOW 1000 FT AND SAID I WAS TURNING IN TOWARDS THE ONCOMING TFC; WHICH I ALSO CORRECTED. I ASKED FOR A VECTOR TO FLY; BUT WAS REFUSED; TELLING ME I WAS 'ON DOWNWIND.' I ASKED FOR TWR TO CALL MY BASE; WHICH AFTER A WHILE; THEY RELUCTANTLY DID. ONCE TURNING BASE; THE ARPT WAS IN SIGHT; AND THE REST OF THE APCH AND LNDG WAS UNEVENTFUL. HERE'S MY ANALYSIS OF THE SIT -- WHAT WENT WRONG AND WHAT SHOULD HAVE BEEN DIFFERENT: I DIDN'T KNOW MY GPS' APCH MODE WELL ENOUGH. LATER; I USED THE PC SIMULATOR MORE; FIGURED OUT WHAT HAD HAPPENED; AND LEARNED HOW TO CHOOSE AN IAF (WHEN AVAILABLE); AND HOW TO PROGRAM FOR 'VECTORS TO FINAL.' IT MIGHT HAVE BEEN BETTER TO TAKE THE MISSED APCH; SINCE I WOULD HAVE STAYED IN 'IFR MODE.' HOPEFULLY; I WOULD HAVE KEPT UP ENOUGH TO TRY THE VOR APCH; OR TAKE THE VISUAL. I SHOULD HAVE HAD THE VOR DIALED IN AS BACKUP. I WOULD HAVE HAD LATERAL GUIDANCE AND DISTANCE. I SHOULD HAVE STUDIED THE SMO VICINITY MORE CAREFULLY ON THE VFR CHARTS BEFORE FLYING THERE; SO THE LONG DOWNWIND WOULDN'T HAVE BEEN AS HARD TO FIGURE OUT. I ALSO SHOULD HAVE SWITCHED TO THE VFR CHARTS IMMEDIATELY. THE PC SIMULATOR; AND THE DOCS FOR IT AND GPS ITSELF ARE POOR. IT'S VERY DIFFICULT TO FIGURE OUT HOW TO PLACE THE SIMULATED ACFT IN THE RIGHT PLACE AND CONFIGURE THE SIMULATOR TO EXERCISE THE APCH FACILITY. THE DOCS ALSO DON'T EXPLAIN THE APCH FUNCTIONALITY WELL; AND ARE REALLY ONLY CLEAR ONCE YOU HAVE ALREADY FIGURED OUT HOW EVERYTHING WORKS. THE GX60 INTERFACE IS NOT INTUITIVE. FOR SMO; IT LISTS A SET OF FIXES; BUT DOESN'T ALLOW YOU TO PICK A DIFFERENT ONE. THE ONLY INDICATION OF THIS IS THAT THE DIAL 'DOES NOTHING.' SINCE THE FONT IS SMALL; IT'S HARD TO NOTICE THIS. YOU HAVE TO SELECT THE FULL APCH; AND KNOW THAT YOU SHOULD THEN HIT THE [SEL] BUTTON TO GET A CHOICE OF 'VECTORS TO THE APCH' INSTEAD. I WANT TO BE ABLE TO PICK ANY FIX; IN CASE I NEED TO SWITCH THINGS AROUND AT THE LAST MINUTE. ATC SHOULD HAVE LET ME CIRCLE; LOSE ALT; AND LAND. I WAS SET UP FOR THAT (BASICALLY A CIRCLING APCH). INSTEAD THEY SENT ME AWAY FROM THE ARPT VFR FOR AN EXTENDED PERIOD OF TIME; FORCING ME TO NAVIGATE IN AN AREA I'M UNFAMILIAR WITH; AND NEAR CLASS C AND B AIRSPACE THAT I SUDDENLY HAVE TO WORRY ABOUT; BEING VFR. SINCE THEY HAD ME ON RADAR; THEY COULD HAVE GIVEN ME A VECTOR TO FLY TO HELP ME OUT; AND BEEN MORE WILLING TO CALL MY BASE.

Data retrieved from NASA's ASRS site as of January 2009 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.