A FOREIGN CARGO B747-400 RECEIVED A TCASII ALERT ON A CARGO MD11 WHO WAS 2000 FT BELOW. THE B747 RESPONDED TO AN RA WITH A CLB AND THEN A DSCNT AND CAUSED LTSS TO OCCUR. THE MD11 HAD VISUAL CONTACT WITH THE B747 AND THE ARTCC CTLR DSNDED THE MD11 FURTHER BELOW THE B747 TO ELIMINATE ANY FURTHER FALSE TCASII ALERTS.

Narrative

I WAS TRAINING A RADAR TRAINEE ON ANCHORAGE ARTCC'S OCEANIC SECTORS. ALL SECTORS WERE COMBINED TOGETHER AND TFC WAS BUSY. ACR X (B747) WAS INBOUND TO ANC AT FL350. THERE WAS ALSO A NON TCASII EQUIPPED ACR Y (MD11) UNDERNEATH ACR X AT FL330. THE ACR X ACFT BROADCAST 'ACR X RA; RA.' WE HAD NO TFC OTHER THAN THE ACR Y; MD11; UNDERNEATH HIM. THE ACR Y; MD11; WAS IN LEVEL FLT WITH A VALID MODE C OF FL330. THE ACR X ACFT CLBED TO FL355 THEN DSNDED RAPIDLY TO FL336-FL333. ACR X WAS ADVISED OF THE ACR Y TFC AND ACR Y ADVISED HE HAD ACR X IN SIGHT. ACR X THEN CLBED BACK TO FL344 AND EXPERIENCED IN HIS LANGUAGE 'MOMENTARY LOSS OF CTL' AND DSNDED AGAIN TO FL336. ACR Y WAS DSNDED TO FL310 AND ADVISED OF THE PROB WITH ACR X. I BELIEVE THE ACR X; B747; HAD A FALSE TCASII ALERT FROM HIS OWN XPONDER AND THAT IF ACR Y HAD BEEN EQUIPPED WITH TCASII THE ACFT WOULD NOT HAVE GOTTEN SO CLOSE. CONFLICT ALERT ONLY WORKS FOR ATC IF YOU HAVE AN IDEA OF WHAT THE PROB IS. 2 LEVEL ACFT GOING INTO CONFLICT ALERT WITH NO OTHER TFC JUST INDICATES A 'NORMAL' FLOW IN THE SYS.