NMAC.

Narrative

ACFT 1 AND ACFT 2 WERE ON A FORMATION AEROBATIC PRACTICE FLT AT APPROX 3600 FT MSL. ACFT 2 WAS ON THE R WING OF ACFT 1; SEPARATED BY APPROX 50 FT. THE FORMATION WAS HEADED SE AND INITIATED A SHALLOW DSCNT TO GAIN REQUIRED AIRSPD FOR ENTRY INTO A LOOPING MANEUVER. THE LEAD ACFT (ACFT 1) WAS IN INVERTED FLT. ACFT 2 WAS IN UPRIGHT FLT. THE ACFT (1 AND 2) WERE IN RADIO COM WITH THE LEAD ACFT (ACFT 1) CALLING PITCH CHANGES TO THE WING ACFT. AFTER GAINING THE REQUIRED AIRSPD IN THE DSCNT TO 3400 FT MSL; ACFT 1 RESUMED LEVEL (INVERTED) FLT. AT THAT TIME ACFT 3 WAS SIGHTED SLIGHTLY BELOW AND IN FRONT OF ACFT 1 ON A RECIPROCAL HDG. ACFT 1 INITIATED A SHALLOW (INVERTED) CLB TO INCREASE THE VERT SEPARATION FROM ACFT 3. ACFT 3 PASSED BELOW THE FORMATION BY APPROX 50-100 FT. IT IS UNKNOWN IF ACFT 3 EVER SAW THE OTHER ACFT. THE DARK (GRAY/GREEN) COLOR OF ACFT 3 WAS DIFFICULT TO PICK OUT AGAINST THE BACKGND; SAN FRANCISCO BAY. THE PITCH ANGLE OF ACFT 1 ALONG WITH THE WING AND FUSELAGE CONFIGN PUT ACFT 3 IN A BLIND SPOT DURING THE INVERTED DSCNT. FORMATION CONFIGN MADE ABRUPT; ROLLING EVASIVE ACTION IMPOSSIBLE.