Narrative:

We were an small aircraft flying at 4500 ft exiting the los angeles special flight rules area nwbound. Pilot contacted smo tower and was cleared to enter the air traffic area via a descent to 2200 ft and to turn eastbound. As we continued a right descending turn from a heading of 312 degrees to 070 degrees, passing through 3500 ft, a t- tail twin engine aircraft was seen on a collision course. The passenger in the right seat spotted the aircraft and notified the pilot. The pilot immediately pitched down to pass beneath the twin. Approximately -0.5 G's was aircraft load factor experienced during pitchover. Engine noise from the twin could be heard in our cabin as it passed overhead. Contributing factors: twin seemed to be on a course to enter the los angeles sfra via the smo VOR 132 degree radial at 3500 ft on a seasterly heading. Our small aircraft was exiting the sfra on the 312 degree radial at 4500 ft. To avoid the TCA later on the route, our aircraft required a descent from 4500 ft, through the VFR cruising altitude of 3500 ft, to the eward altitude of 2200 ft final altitude. Head on collision possibilities occur on the VOR radial with a descending aircraft passing through other VFR cruising altitudes. It is not known whether our aircraft was on the VOR radial or offset to the east. It is also not absolutely known whether the near miss occurred at exactly 3500 ft. Low time pilot. Pilot was visually confirming landmarks for pilotage navigation. This needs to be combined with horizon scan in congested airspace. Experience helps. Alternate route nwward through the TCA via the la shoreline route denied to pilot by los angeles approach controller due to traffic congestion. This clearance would have helped us avoid large climbs or dscnts from our initial 2500 ft en route altitude. Corrective actions: pitch down to avoid approaching aircraft. Diversion to right too slow and not practical at that instant. 2-3 seconds elapsed between control input and aircraft passing overhead. Approximately -0.5 G load factor was experienced. Perceptions, judgements, decisions: pilot was descending and scanning landscape for pilotage/navigation. Attention diverted and aircraft scan pattern was altered. Awareness of aircraft traffic rtes was not constantly kept in mind. Upon visual contact with traffic, quick decision was made to descend since it is faster to descend than to climb or turn right. Concern was if other aircraft also decided to descend for collision avoidance. Other aircraft took no action and continued straight and level.

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Original NASA ASRS Text

Title: NMAC IN A VFR CORRIDOR OF A TCA. BTWN AN SMA AND SMT ACFT.

Narrative: WE WERE AN SMA FLYING AT 4500 FT EXITING THE LOS ANGELES SPECIAL FLT RULES AREA NWBOUND. PLT CONTACTED SMO TWR AND WAS CLRED TO ENTER THE ATA VIA A DSCNT TO 2200 FT AND TO TURN EBOUND. AS WE CONTINUED A R DSNDING TURN FROM A HDG OF 312 DEGS TO 070 DEGS, PASSING THROUGH 3500 FT, A T- TAIL TWIN ENG ACFT WAS SEEN ON A COLLISION COURSE. THE PAX IN THE R SEAT SPOTTED THE ACFT AND NOTIFIED THE PLT. THE PLT IMMEDIATELY PITCHED DOWN TO PASS BENEATH THE TWIN. APPROX -0.5 G'S WAS ACFT LOAD FACTOR EXPERIENCED DURING PITCHOVER. ENG NOISE FROM THE TWIN COULD BE HEARD IN OUR CABIN AS IT PASSED OVERHEAD. CONTRIBUTING FACTORS: TWIN SEEMED TO BE ON A COURSE TO ENTER THE LOS ANGELES SFRA VIA THE SMO VOR 132 DEG RADIAL AT 3500 FT ON A SEASTERLY HDG. OUR SMA WAS EXITING THE SFRA ON THE 312 DEG RADIAL AT 4500 FT. TO AVOID THE TCA LATER ON THE RTE, OUR ACFT REQUIRED A DSCNT FROM 4500 FT, THROUGH THE VFR CRUISING ALT OF 3500 FT, TO THE EWARD ALT OF 2200 FT FINAL ALT. HEAD ON COLLISION POSSIBILITIES OCCUR ON THE VOR RADIAL WITH A DSNDING ACFT PASSING THROUGH OTHER VFR CRUISING ALTS. IT IS NOT KNOWN WHETHER OUR ACFT WAS ON THE VOR RADIAL OR OFFSET TO THE E. IT IS ALSO NOT ABSOLUTELY KNOWN WHETHER THE NEAR MISS OCCURRED AT EXACTLY 3500 FT. LOW TIME PLT. PLT WAS VISUALLY CONFIRMING LANDMARKS FOR PILOTAGE NAV. THIS NEEDS TO BE COMBINED WITH HORIZON SCAN IN CONGESTED AIRSPACE. EXPERIENCE HELPS. ALTERNATE RTE NWWARD THROUGH THE TCA VIA THE LA SHORELINE RTE DENIED TO PLT BY LOS ANGELES APCH CTLR DUE TO TFC CONGESTION. THIS CLRNC WOULD HAVE HELPED US AVOID LARGE CLBS OR DSCNTS FROM OUR INITIAL 2500 FT ENRTE ALT. CORRECTIVE ACTIONS: PITCH DOWN TO AVOID APCHING ACFT. DIVERSION TO R TOO SLOW AND NOT PRACTICAL AT THAT INSTANT. 2-3 SECONDS ELAPSED BTWN CTL INPUT AND ACFT PASSING OVERHEAD. APPROX -0.5 G LOAD FACTOR WAS EXPERIENCED. PERCEPTIONS, JUDGEMENTS, DECISIONS: PLT WAS DSNDING AND SCANNING LANDSCAPE FOR PILOTAGE/NAV. ATTN DIVERTED AND ACFT SCAN PATTERN WAS ALTERED. AWARENESS OF ACFT TFC RTES WAS NOT CONSTANTLY KEPT IN MIND. UPON VISUAL CONTACT WITH TFC, QUICK DECISION WAS MADE TO DSND SINCE IT IS FASTER TO DSND THAN TO CLB OR TURN R. CONCERN WAS IF OTHER ACFT ALSO DECIDED TO DSND FOR COLLISION AVOIDANCE. OTHER ACFT TOOK NO ACTION AND CONTINUED STRAIGHT AND LEVEL.

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.