Medium Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1
Human-Machine Interface
ATC Issue All Types; Aircraft Equipment Problem Less Severe
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Equipment / Tooling; ATC Equipment / Nav Facility / Buildings; Aircraft
While working a routine/normal sequence to the LAX 'North Final 24R' which is considered the 'Stadium' position; I vectored Aircraft X from the DARTS way point to the downwind to follow another aircraft. While on the modified downwind vector; I noticed Aircraft X 'data tag' or 'secondary' go into 'coast' or 'CST' mode. I also noticed that the primary target disappeared. Even though I noticed it; I didn't give it much attention because I figured the secondary would re-acquire and go back to normal. But that's not what happened; within 5 seconds of going into 'CST' mode; the secondary completely disappeared along with the primary target.I was totally caught off guard by this and began to question the pilot about his transponder status. With prompting from a fellow controller; I told the pilot; 'radar contact lost'. The pilot responded by saying he was; 'climbing back up to five thousand.' Not sure why he did that; but I acknowledged by saying 'roger' and I continued to work my sequence while also trying to figure out what type of non-radar service I was going to provide the pilot. But within 15-20 seconds; the primary target began to reappear and within another 10 seconds; the secondary re-acquired. From there I had the pilot 'ident' and I radar identified him and continued to work him into my flow. Once I vectored him onto the final I asked the pilot what happened to his transponder and he responded by saying; 'the number one transponder failed'. I guess that's why we lost the secondary target; but it doesn't explain why we would lose the primary target as well for as long as we did.With limited knowledge on what could have caused this issue; my instincts tell me this was a Standard Terminal Automation Replacement System (STARS) malfunction of some sort. Even if an aircraft loses their secondary radar capabilities; our radar equipment should still provide us with a primary return and in this case; it did not.
SCT TRACON Controller reported losing the data tag; secondary beacon and primary target on an aircraft on downwind. Pilot reported transponder failure when questioned; Controller wondered why all contact was lost and an assumption that it had to do with STARS Radar was made.