B747-400
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer
Flight Crew Last 90 Days 120; Flight Crew Total 25000; Flight Crew Type 10000
Other / Unknown
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew Took Evasive Action
Human Factors; Procedure
Assigned FL370; northbound on Airway A590 about 180 NM south of GURAG Intersection. The Captain was pilot flying. We received a TCAS warning; 'TRAFFIC; TRAFFIC; DESCEND; DESCEND.' The traffic on TCAS was at our 0900 [o'clock] position (aircraft left) about 20 miles; at same altitude. I visually confirmed conflicting traffic in sight (Captain did not see traffic). Captain did TCAS resolution maneuver; and descended. I monitored the descent on TCAS; and observed the conflicting traffic climbing; both on TCAS; and visually. We cleared traffic by 2;200 feet (per TCAS). We climbed back up to FL370; and when level; observed that conflicting traffic (now behind; and to our right) had also returned to FL370.We established contact with conflicting traffic on frequency 123.45. It was a KC135 tanker and he advised his cleared altitude was also FL370. Contacted Manila Radio on HF 8903 to pass along to Manila Control of our resolution advisory maneuver; and to also confirm our cleared altitude. Manila Radio replied our confirmed altitude was FL370.
B747 First Officer experiences a TCAS RA at FL370 on A590 north bound with a KC135 converging from the west at the same altitude. Evasive action is taken by both aircraft. Both aircraft were apparently at their correct altitude as assigned by Manila Control.