RV-12
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Conflict NMAC
Flight Crew Took Evasive Action
Procedure; Human Factors
I was providing RADAR advisory services for VFR Aircraft X; a RV12/G enroute eastbound at 9;500 FT. A fast-moving Mode-C Intruder target was level at 11;500 NW of Aircraft X. I noted that the Mode-C intruder had descended to 10;500 FT and appeared to have leveled there for quite some time. Due to the fast rate of speed of that target; I made a traffic call to Aircraft X; noting traffic was at 7 to 8 o'clock and 5 miles at 10;500 FT; altitude unverified and type unknown; overtaking; and passing north to south. Aircraft X reported the traffic in sight. At some point; I commenced giving a position relief briefing. During the briefing; the Mode-C Intruder started descending into Aircraft X. Around the same time; there was a large number of track jumps; and the Mode-C Intruder was in close proximity with Aircraft X. I immediately issued a traffic alert to Aircraft X giving an approximate position due to the track jumps; apparent Mode-C swaps; and Aircraft X's vector line spinning quickly clockwise; either due to RADAR anomaly; or pilot action. There was no response to the traffic alert. Roughly 15 seconds later; the pilot noted that he had taken evasive action; and that the traffic was really close. I asked if the pilot of Aircraft X had seen the aircraft type of the other aircraft; and he responded that it was a large 4 engine prop; possibly an [P3] Orion. Following the incident; the Mode-C intruder continued to descend and turn westbound toward the Big Bear (L35) Airport. I immediately reported the event to Management; the only aircraft that landed within that time period was a Cheyenne. The pilot of the Cheyenne was apparently questioned and noted that he did not see any traffic during the descent.
ZLA Controller described a conflict event involving an apparent military aircraft and a VFR transiting aircraft at 9;500 FT; the identity of the second aircraft was never determined.