DRG AEROBATICS, THE ACFT WENT IN A DIVE, GAINED SPEED, LEVELED OFF & PULLED UP ABRUPTLY. DRG THE PULL-UP, THE RGT WING FAILED UPWARD & SEPD FM THE ACFT. THE ACFT THEN WENT OUT OF CTL & CRASHED. THE PLT WAS WEARING A PARACHUTE, BUT DID NOT BAIL-OUT; HE WAS FOUND STRAPPED IN HIS SEAT & THE DOOR RLS PIN WAS STILL IN PLACE. THERE WAS EVIDENCE OF UPWARD BENDING OF THE LEFT WING; BOTH HORIZONTAL STABILIZERS HAD EVIDENCE OF BEING COMPROMISED IN A DWNWRD DRCTN. AN EXAM OF THE PLT'S SEAT REVEALED THE TUBULAR ENDS OF THE SEAT-BACK FRAME HAD FAILED AT THE PIVOT POINTS (PVT PTS), WHERE THE SEAT-BACK WAS DESIGNED TO PIVOT FWD OVR THE SEAT PAN TO ALLOW ENTRY TO THE AFT SEAT. ATTACHING BOLTS AT THE PVT PTS HAD PULLED THRU THE ENDS OF THE FRAME. EVIDENCE OF OVERSTRESS SHEAR WAS FND AT THE RGT PVT PT AS IF THE SEAT-BACK HAD FAILED AFT. EVIDENCE OF OVERSTRESS SHEAR & TWISTING DEFORMATION WAS FND AT THE LEFT PVT PT. BELLANCA 7 & 8 SERIES ACFT HAVE HAD SVRL SEATBACK FAILURES AT THE HINGE POINT OR AT THE WELDED JUNCTION OF THE SEAT'S LOWER SIDE TUBE & SEATBACK SIDE BRACE.