Narrative:

Our aircraft was part of many general aviation planes on display at dulles days. We departed iad on a sfra/VFR fight plan towards casanova VOR (csn); followed by a turn towards fluke intersection. After exiting the sfra we went VFR; but due to the general busy nature of GA aircraft in the vicinity; we picked up flight following at fluke. We were cruising at 2500 ft MSL with some scattered clouds above us; towards ofp. A few minutes past fluke our onboard adsb indicated a plane below; at; and 1000 ft+ above us within 1-2 seconds. We received a notice from potomac approach that we had unknown aircraft very close to us; but moments later told to disregard that warning. At the same time; a nearby aircraft reported issue with transponder and; given the erratic notifications on the instruments display; and the disregard notice from potomac; that not many planes can climb 1000 ft in a about a second; and the adsb reporting traffic approximately 6 miles away which we thought we had the warning on; we assumed this was simply a data malfunction. I radioed potomac and advised that I also had erratic data on screen and confirm the confusion. Without a doubt; the controller was puzzled and concerned. Moments later we received another traffic warning; while flying below some clouds. This time; the controller advised take immediate evasive action and turn west; as there was traffic above us closing in. We dove and turned west. Only then did my rear passenger spot the culprit; a plane doing aerobatics popping in and out of the cloud layer. The adsb warning - unknown to me - is on a delay. Moments after the passenger had a visual from the rear window; 300 ft above aircraft warning displayed on my instrument. Controller confirmed 300 ft separation at one point. We notified potomac of the situation and they began rerouting traffic. After resuming course and switching frequencies to the next controller about 10 miles down; I also advised that controller of the circumstances behind me. Although we were flying not too far from culpepper and flying circus; I am well aware of the aerobatics in the region. My planned route put me clear of all of that; or so I thought. I also assumed that the only traffic in the clouds above me would be IFR. Clearly that assumption; along with many of the day's events; nearly lead to an accident chain that could have claimed the lives of 3 people in my aircraft; and the irresponsible pilot that nearly collided into us doing aerobatics in and out of the clouds. I want to be very - very clear - my 300 ft warning was displayed when there were clouds above me; which I was flying easily 1000 ft below. The passenger watched the aerobatics plane do loops in and out of the scattered layer.

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Original NASA ASRS Text

Title: GA pilot reported an NMAC with an aircraft doing aerobatics in and out of a cloud layer.

Narrative: Our aircraft was part of many general aviation planes on display at Dulles Days. We departed IAD on a SFRA/VFR fight plan towards CASANOVA VOR (CSN); followed by a turn towards FLUKE intersection. After exiting the SFRA we went VFR; but due to the general busy nature of GA aircraft in the vicinity; we picked up flight following at FLUKE. We were cruising at 2500 ft MSL with some scattered clouds above us; towards OFP. A few minutes past FLUKE our onboard ADSB indicated a plane below; at; and 1000 ft+ above us within 1-2 seconds. We received a notice from Potomac Approach that we had unknown aircraft very close to us; but moments later told to disregard that warning. At the same time; a nearby aircraft reported issue with transponder and; given the erratic notifications on the instruments display; and the disregard notice from Potomac; that not many planes can climb 1000 ft in a about a second; and the ADSB reporting traffic approximately 6 miles away which we thought we had the warning on; we assumed this was simply a data malfunction. I radioed Potomac and advised that I also had erratic data on screen and confirm the confusion. Without a doubt; the controller was puzzled and concerned. Moments later we received another traffic warning; while flying below some clouds. This time; the controller advised take immediate evasive action and turn west; as there was traffic above us closing in. We dove and turned west. Only then did my rear passenger spot the culprit; a plane doing aerobatics popping in and out of the cloud layer. The ADSB warning - unknown to me - is on a delay. Moments after the passenger had a visual from the rear window; 300 ft ABOVE aircraft warning displayed on my instrument. Controller confirmed 300 ft separation at one point. We notified Potomac of the situation and they began rerouting traffic. After resuming course and switching frequencies to the next controller about 10 miles down; I also advised that controller of the circumstances behind me. Although we were flying not too far from Culpepper and Flying Circus; I am well aware of the aerobatics in the region. My planned route put me clear of all of that; or so I thought. I also assumed that the only traffic in the clouds above me would be IFR. Clearly that assumption; along with many of the day's events; nearly lead to an accident chain that could have claimed the lives of 3 people in my aircraft; and the irresponsible pilot that nearly collided into us doing aerobatics in and out of the clouds. I want to be very - very clear - my 300 ft warning was displayed when there were clouds above me; which I was flying easily 1000 ft below. The passenger watched the aerobatics plane do loops in and out of the scattered layer.

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.