Date: 201705
Local time of day: 0001-0600
Location: VECF.ARTCC, FO
Weather elements / visibility: Turbulence; Thunderstorm
Light: Night
Aircraft: B747 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
Airspace: Class A VECF
ATC / advisory: Center VECF
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Relief Pilot; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Situational Awareness; Other / Unknown
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Returned To Clearance
Contributing factors: Human Factors; Weather
Primary problem: Ambiguous

Narrative: Approaching LKN; observed CB WX approx 20 NM other side of LKN extending approx 20-30 NM both sides of LKN. Deviated to the left near KADAS [R460] with an offset 30 miles left. At approx 160 NM from LKN there was another line of WX extending approx 30 miles S of track (We were now 30 N of track) and approx 150 NM N of track. From this position; Pilot Flying insisted on turning north even further. My preference was to turn south; split the two areas of WX; and then turn back left on the south side. He felt the radar was attenuating and that we absolutely could not go that way. We took up a heading of 060 degrees. Shortly afterwards; it became very turbulent; and the Captain returned to the flight deck. We were just above the under cast this entire time. We continued north in spite of continued request to turn right from Kolkata. We went as far left as 040 heading. Kolkata tried to hand us off to Kathmandu; but we were unable to establish contact. Kolkata advised that in 10 NM we would be entering Chinese airspace. They still refused to turn right. North of VNKT; we finally started working our way around to the right. We ended up somewhere between 150-160 NORTH of our intended track. While not exact; I feel we were in Chinese airspace for a short period of time. When we were established direct MONDA; it was approx a 170 heading. We crossed MONDA at -21 on time and down .4 on fuel. We were +2.9 on fuel crossing abeam LKN and on time. I feel the course to the south would have been far superior to what actually occurred. The First Officer's (PF) insistence that the radar was attenuating and that we couldn't see what was on the other side to the south precipitated this event. I never saw any WX south of what was being painted around LKN and 160 NM beyond. Even after we went left around the first cells; I felt it would have been more prudent to turn south and split the two; remaining in Kolkata airspace. ICI was a concern; but as indicated before; we were just above the tops the entire time. I was unaware that I was PIC during this time period. The PF (First Officer) was the senior First Officer so I incorrectly assumed the Captain had designated him. I was not ask to sign in on the OFP and was not aware until I looked at it on descent in HKG when I realized I had been 'signed in.'




Synopsis: B747 relief pilot did not realize that he had been designated PIC while the Captain was on break; and allowed the First Officer to make a weather deviation decision that took them 160 NM north of course and possibly into Chinese airspace.