Narrative:

This involves what I believe to be a near miss. This happened after flying from catalina island, across the la basin, under a section of the TCA, all at legal altitude and with no question of my position. After arriving at a point indicated, I began flying 360 degree turns in level flight around a ground reference point. On the third or fourth revolution, a small orange helicopter passed below me. I don't know if the pass was intentional or accidental, or if he even considered it a near miss. However, for the sake of this report, I will assume it was unintentional. While turning I was also keeping an eye out for traffic, which I never saw in this case until he became visible in the right side window as I looked down. Judging by the direction he was going at the the time, he apparently came up from behind me, but off to my right while I was headed west. As I continued my turn his position would be blocked from view by my right wing. Then, as my turn continued around to the east, he passed under me. I speculate that he could have come over a ridge of hills to the east at less than 1000' AGL. At this altitude he may have not been looking for other aircraft, believing that he was below the 1000' AGL minimum for city flight. However, after clearing the adjacent hilltops, he was over a valley floor which put him closer to 1000' AGL. For myself, I don't know what I could have done any differently to see him. I was devoting a considerable amount of time looking out the windshield and 2 side windows for other aircraft. The only other think that might avoid this kind of incident is to not do vision-blocking maneuvers near slightly higher terrain where a helicopter might be lulled into thinking he is safe from other aircraft.

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Original NASA ASRS Text

Title: SMA PERFORMING 260 DEGREE TURNS AROUND A FIX AT LOW ALT HAS NMAC WITH HELICOPTER.

Narrative: THIS INVOLVES WHAT I BELIEVE TO BE A NEAR MISS. THIS HAPPENED AFTER FLYING FROM CATALINA ISLAND, ACROSS THE LA BASIN, UNDER A SECTION OF THE TCA, ALL AT LEGAL ALT AND WITH NO QUESTION OF MY POS. AFTER ARRIVING AT A POINT INDICATED, I BEGAN FLYING 360 DEG TURNS IN LEVEL FLT AROUND A GND REF POINT. ON THE THIRD OR FOURTH REVOLUTION, A SMALL ORANGE HELI PASSED BELOW ME. I DON'T KNOW IF THE PASS WAS INTENTIONAL OR ACCIDENTAL, OR IF HE EVEN CONSIDERED IT A NEAR MISS. HOWEVER, FOR THE SAKE OF THIS RPT, I WILL ASSUME IT WAS UNINTENTIONAL. WHILE TURNING I WAS ALSO KEEPING AN EYE OUT FOR TFC, WHICH I NEVER SAW IN THIS CASE UNTIL HE BECAME VISIBLE IN THE RIGHT SIDE WINDOW AS I LOOKED DOWN. JUDGING BY THE DIRECTION HE WAS GOING AT THE THE TIME, HE APPARENTLY CAME UP FROM BEHIND ME, BUT OFF TO MY RIGHT WHILE I WAS HEADED W. AS I CONTINUED MY TURN HIS POS WOULD BE BLOCKED FROM VIEW BY MY RIGHT WING. THEN, AS MY TURN CONTINUED AROUND TO THE E, HE PASSED UNDER ME. I SPECULATE THAT HE COULD HAVE COME OVER A RIDGE OF HILLS TO THE E AT LESS THAN 1000' AGL. AT THIS ALT HE MAY HAVE NOT BEEN LOOKING FOR OTHER ACFT, BELIEVING THAT HE WAS BELOW THE 1000' AGL MINIMUM FOR CITY FLT. HOWEVER, AFTER CLRING THE ADJACENT HILLTOPS, HE WAS OVER A VALLEY FLOOR WHICH PUT HIM CLOSER TO 1000' AGL. FOR MYSELF, I DON'T KNOW WHAT I COULD HAVE DONE ANY DIFFERENTLY TO SEE HIM. I WAS DEVOTING A CONSIDERABLE AMOUNT OF TIME LOOKING OUT THE WINDSHIELD AND 2 SIDE WINDOWS FOR OTHER ACFT. THE ONLY OTHER THINK THAT MIGHT AVOID THIS KIND OF INCIDENT IS TO NOT DO VISION-BLOCKING MANEUVERS NEAR SLIGHTLY HIGHER TERRAIN WHERE A HELI MIGHT BE LULLED INTO THINKING HE IS SAFE FROM OTHER ACFT.

Data retrieved from NASA's ASRS site as of August 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.