Date: 201307
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: T6A Texan II / Harvard II (Raytheon)
Reporter organization: Government
Reporter function: Approach; Departure
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Time Pressure; Workload; Situational Awareness; Communication Breakdown
Anomaly: Conflict Airborne Conflict; Deviation / Discrepancy - Procedural FAR
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Airspace Structure; Human Factors
Primary problem: Human Factors

Narrative: I was working the East Arrival position with moderate to heavy traffic. The weather was VFR. I took a handoff on an E145 that was descending to 11;000 FT and 250 KTS. The aircraft was inbound for landing and Runway 26 was in use. When the E145 checked in I descended the aircraft to 8;000 FT. Shortly thereafter the E145 advised that he had a Near Mid Air Collision (NMAC) with a turboprop at or around 10;000 FT. I did not issue traffic on a target that I observed after the E145 declared the NMAC. I was very busy at this time and the traffic that I observed after was a VFR aircraft that appeared to be doing aerobatic maneuvers within the confines of [two victor airways]; between the altitudes of 8;000 and 10;500 FT. After the pilot declared the NMAC; I asked the Supervisor in charge at the time for a Radar Handoff/Assist due to extreme workload and moderate to heavy traffic; and received a help shortly after; and all service was normal without further issues. I also advised the Supervisor that the pilot had declared a NMAC on frequency at the time of the incident. I asked to be relieved from position and was relieved of position. I then listened to the voice replay of the incident and then the radar replay of the incident. At the time this occurred I did not observe the traffic being a factor for the E145 and did not issue the traffic; due to workload. When reviewing the radar; I noticed that shortly after this the VFR aircraft called another sector and was positively identified as a VFR Texan that is based out of [a nearby military] airport. I believe that the Texan was performing aerobatics within the confines of an airway outside of Class Charlie airspace; which is very crucial piece of airspace due to arriving and departing aircraft entering and exiting our airspace. I was told that the Military understands the high volume of traffic in this area and are briefed to not perform aerobatics in this area; as they have a north and south MOA in our airspace that has been delegated for their pilots to do these types of maneuvers. I believe a briefing should be sent to the [military airports] squadrons ASAP to prevent further issues such as these.




Synopsis: A Local Controller received a report of an NMAC between and E145 under his control and a turboprop aircraft later identified as a VFR Beechcraft T6-A Texan military trainer that appeared to be performing aerobatics.