Cessna 340/340A
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Procedure
Aircraft departed LGB IFR; was climbed to 6;000 feet and turned on course via SLI; SLI058R (Anaheim Departure LHS transition). Aircraft was then handed off to Pacific RADAR Sector and shipped to Pacific's frequency. I later observed the aircraft pop out of the 'main bang' (Garden Grove RADAR site located approx. 3 miles East of SLI) at 7;000 feet and climbing. I questioned the Pacific Controller and learned that he was already querying the pilot. After this event was reviewed; we determined that the pilot had mistakenly begun a climb to 8;000 feet vs. 6;000 feet as assigned.  Because of the RADAR antenna location; we always lose RADAR on these aircraft for approximately 5 miles. LAX arrival aircraft cross over SLI at 7;000 feet continuously and are then vectored to the LAX final. It was fortunate that there were no aircraft in conflict at this time. There was no way to observe the erroneous climb. Pilot was issued the Brasher Notification and did contact the facility. He advised that he made a mistake. Our facility is in the process of certifying FUSION. The sooner the better. The pilot was advised that he needs to check in with his current altitude and assigned altitude on every transmission for safety. On initial contact with ATC the pilot never reported altitude and assigned altitude. I'm not sure how he checked in on Pacific RADAR.
SCT Controller described the loss of altitude information due to a 'main bang' transition; the reporter hopeful that 'FUSION' RADAR will solve this long standing problem.