SA227 CREW HAD AN NMAC WITH AN F18 IN MIL AIRSPACE.

Narrative

THIS RPT IS TO THE BEST OF MY RECOLLECTION AS THE FO AND PF. WE WERE ON AN IFR FLT PLAN FLYING FROM NAVY SAN CLEMENTE ISLAND TO NAVY NORTH ISLAND ON AN ASSIGNED HDG OF 110 DEGS AND LEVEL AT OUR CRUISE ALT OF 5000 FT MSL. AT THE TIME WE WERE UNDER BEAVER CTL WITH A NORMAL IFR XPONDER CODE. OUR TCASII ALERTED DUE TO TFC ON OUR 6 O'CLOCK POS AND 500 FT BELOW US. WHILE NOTICING THAT THE TFC WAS GETTING CLOSER AND BECOMING OUR SAME ALT; BEAVER CTL ANNOUNCED THE TFC AND SAID THAT THEY WERE NOT TALKING TO THE ACFT BUT THAT IT WAS AN F18. AFTER DETERMINING THAT THERE WAS DEFINITELY A MIDAIR COLLISION THREAT; I PITCHED DOWN SHARPLY TO AVOID THE TFC AND THEN I NOTICE THAT THE TFC SEEMED TO BE DESCENDING RAPIDLY WITH US. WHILE IT WAS STILL CLOSING IN; I THEN BANKED SHARPLY TO THE L AND TURNED ABOUT 30 DEGS. OUR ATTITUDE WAS ABOUT 15 DEGS PITCH DOWN AND ABOUT 45 DEGS OF L BANK. ABOUT 3 SECONDS AFTER THAT; AND DSNDING THROUGH 2600 FT MSL; THE F18 PASSED ABOUT 300 FT OVER THE TOP OF US. THE ACFT PASSED OVER US FROM OUR 7 O'CLOCK POS TO OUR 1 O'CLOCK POS. WE RESUMED OUR NEWLY ASSIGNED HDG OF 090 DEGS AND ALT OF 3000 FT. BEAVER CTL NEVER GAVE US INSTRUCTIONS FOR COLLISION AVOIDANCE. WE ONLY SAW THE ACFT AFTER IT WAS NO LONGER A THREAT DUE TO IT APCHING US FROM BEHIND. I AM NOT SURE IF THIS WAS A POSSIBLE MIDAIR COLLISION SIT. WE TREATED THE EVENT AS IF IT WERE AND ACTED ACCORDINGLY. THE PLT OF THE F18 MAY HAVE CONFUSED US WITH ONE OF HIS 'PLAYMATES' IN A TRAINING EXERCISE. WHETHER HE EVER SAW US OR NOT; WE DO NOT KNOW AT THIS TIME.