Narrative:

I was working the radar position at sector 66/67 combined. Aircraft X was level at 10;000 feet; orlando had already taken an automated radar handoff; direct moans.MINEE5.orl; when the pilot reported a TCAS RA. After he reported the RA; I observed an untracked mode C intruder within [approximately] 3nm of aircraft X; indicating an unverified 10;000 feet. The next radar return indicated 9;100 feet; and I called traffic to aircraft X; 'traffic three to four oclock and two miles; altitude indicating niner thousand one hundred; appears to be descending.' I confirmed that aircraft X had completed his RA; and was on course and at the assigned altitude; and switched him to orlando approach.the untracked mode C intruder was aircraft Y. We recently began operations with them under a memorandum (not a letter of agreement;) dated [removed] detailing use of radar tracks to provide traffic advisories. However; there have been multiple instances of [this type of aircraft] aircraft covered by this LOA not coming up and requesting a code and traffic advisories; and instead just monitoring the frequency. I had assumed the sector shortly before the incident; and had two [of this type] aircraft monitoring; but neither had requested or been assigned a code; or otherwise radar identified. The only time I spoke to either aircraft was when they informed me of their return to ism and ZZZ.high performance aerobatic aircraft operating in lakeland's congested airspace should be required by LOA to be radar identified and in communication with ATC at all times while doing air work.

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Original NASA ASRS Text

Title: A ZMA Controller reported of an airborne conflict between an aircraft under ATC Control and an unknown aircraft. The unknown aircraft was found to be a high speed aircraft that was being worked under a special memorandum. The Controller wanted high speed aircraft to work under a LOA that might stop this problem.

Narrative: I was working the radar position at sector 66/67 combined. Aircraft X was level at 10;000 feet; Orlando had already taken an automated radar handoff; direct MOANS.MINEE5.ORL; when the pilot reported a TCAS RA. After he reported the RA; I observed an untracked Mode C intruder within [approximately] 3nm of Aircraft X; indicating an unverified 10;000 feet. The next radar return indicated 9;100 feet; and I called traffic to Aircraft X; 'Traffic three to four oclock and two miles; altitude indicating niner thousand one hundred; appears to be descending.' I confirmed that Aircraft X had completed his RA; and was on course and at the assigned altitude; and switched him to Orlando Approach.The untracked Mode C intruder was Aircraft Y. We recently began operations with them under a Memorandum (Not a Letter of Agreement;) dated [removed] detailing use of radar tracks to provide traffic advisories. However; there have been multiple instances of [this type of aircraft] aircraft covered by this LOA not coming up and requesting a code and traffic advisories; and instead just monitoring the frequency. I had assumed the sector shortly before the incident; and had two [of this type] aircraft monitoring; but neither had requested or been assigned a code; or otherwise radar identified. The only time I spoke to either aircraft was when they informed me of their return to ISM and ZZZ.High performance aerobatic aircraft operating in Lakeland's congested airspace should be required by LOA to be radar identified and in communication with ATC at all times while doing air work.

Data retrieved from NASA's ASRS site 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.