B747 FLT CREW ENCOUNTERS ANOTHER ACFT AT THEIR ALT AND ON THEIR RTE OF FLT IN FOREIGN AIRSPACE AS THEY TAKE EVASIVE ACTION TO PASS THE OTHER ACFT.

Narrative

B747 FLYING ON IFR FLT PLAN AT FL310 ALONG R456 BTWN BOLUR AND KITAL. POS RPTS WITH MUMBAI ON PRIMARY HF WERE SPORADIC BECAUSE MUMBAI FAILED TO RESPOND; ALONG RTE OF FLT. POS RPTS WERE MADE 'IN THE BLIND' ON VARIOUS HF AND VHF 121.5 AT EVERY MANDATORY POINT. APPROX 100 NM NW OF BOLUR; PF VISUALLY OBSERVED A C5 ABOUT 15 NM AHEAD; AT SAME ALT; APPARENTLY ON THE SAME TRACK. ANOTHER ATTEMPT TO CONTACT MUMBAI RADIO WITHOUT SUCCESS. B747 GRADUALLY OVERTOOK C5. PF DEVIATED B747 TO L OF TRACK IN ORDER TO KEEP 5-6 NM DISTANCE BTWN ACFT. RADIO CONTACT WAS ESTABLISHED WITH MUSCAT APPROX 100 NM PRIOR TO KITAL BECAUSE OF THE INABILITY TO CONTACT MUMBAI. AFTER PASSING C5 AND RETURNING TO TRACK. MUMBAI CONTACTED B747 VIA SELCAL. MUMBAI ORDERED B747 TO DSND TO FL280. AFTER CONSULTATION WITH MUSCAT; B747 DSNDED TO FL280. B747 PROCEEDED TO DEST WITHOUT FURTHER INCIDENT. C5 DID APPEAR ON B747'S TCASII WELL AFTER BEING OBSERVED VISUALLY. TCASII DISPLAY WAS USED TO INSURE 5-6 NM OF SEPARATION BTWN ACFT. NO TA OR RA OCCURRED BECAUSE OF DISTANCE MAINTAINED.