A Lear 55 inbound to ADS experienced an NMAC with a group of aerobatic aircraft practicing maneuvers just outside the DFW Class B.

Narrative

On our arrival we were cleared direct to the SASIE intersection to cross at 6;000. Shortly after crossing SASIE we were cleared direct to JERIT intersection and to descend to 4;000. Before reaching 4;000; I saw some 'objects' ahead which I initially thought to be either some birds or a group of released carnival balloons. The closure rate was fairly high and the 'objects' quickly became clearly identified as aircraft. It was a group of at least 4 to 6 aircraft in the process of performing a 'wing over' type maneuver. At the time I saw and identified the group; they were climbing at all were approaching a near 90 degree bank angle relative to the horizon. I would estimate the group to be on an approximate reciprocal heading as was my aircraft. At that point; I stopped our descent and climbed perhaps 200 FT. The formation of aircraft passed below and were not visible at the point where our vertical separation was at it's minimum; 200 to 300 FT. I did not observe any evasive maneuvering by the group or any individual aircraft. My evasive action consisted primarily of stopping descent and climbing. There was no noted change of heading. While the action I took was immediate and firm; it was not violent or abrupt enough to cause any comment of concern from our passengers. I could not identify any of these aircraft only that they were all single-engine; mid-wing; high performance aerobatic aircraft. Based on a subsequent land line conversation with Dallas Approach; it appears that none of these aircraft were Mode C equipped. This is why our operating TCAS did not provide any advisory or warning.This event occurred near Celina; Texas which is on the outer boarder of the Class B Airspace. It is also just inside the 30 NM ring which requires Mode C transponders for powered aircraft. My suggestion would be that in addition to the limits and restrictions as stated in FAR 91.303 regarding Aerobatic Flight - there should be some requirement to remain WELL CLEAR of Class B Airspace and WELL OUTSIDE the 30 NM Mode C Transponder ring.