B787 flight crew reported a track deviation occurred on their trans-Pacific flight when they programmed a larger than cleared offset to avoid wake from a preceding A380 1000 feet above them.
Synopsis
B787 flight crew reported a track deviation occurred on their trans-Pacific flight when they programmed a larger than cleared offset to avoid wake from a preceding A380 1000 feet above them.
Narrative
After a poor rest break in turbulence I; along with the other Relief Pilot; returned to the fight deck to relieve the flying two pilots. I was the PM/relief pilot operating with the PF/relief pilot on our flight to SYD. At approximately 11 hours into our flight; we had been coordinating weather deviations with control most of the previous four hours for convective buildups around the equatorial zone at the time of the error. Our flight ended up getting trapped 1000 ft below an A380 on our routing which added difficulty circumnavigating the weather and staying out of their wake. As we approached YBBB Center FIR we had returned to course with a 0NM SLOP (Strategic Lateral Offset Procedure) to avoid the A380 wake who appeared SLOP'd R2.0NM. The A380 appeared to correct back to centerline as we started flying in their wake again and decided to SLOP R2 and upwind. Communication broke down and R3 was programmed and executed. We departed the dirty air from the A380 and shortly after switched over to YBBB Center and now finally diverging from the A380 were cleared to climb. YBBB then queried us that they were showing offset R3 in ADS-C reporting. We concurred with ATC's advisement and promptly corrected back to R2. We discussed the situation and identified the confusion and breakdown in SOP.
Second reporter narrative
Post rest break; I took over as Relief Pilot/PF. We coordinated weather deviations of up to 100nm right of course equatorial zone with center. We were restricted in our ability to climb by an A380 1000' above us along our track. Upon returning to our route; we began overtaking the A380. The A380 appeared to be SLOP (Strategic Lateral Offset Procedure) R2.0; so we returned to the route to offset to the left. This was not ideal; as the wind was blowing right to left. The A380 crossed our flight path gradually; so we decided to offset R2.0 upwind; to the right. I made an error and entered and executed R3.0. We returned our attention to the traffic and its wake; thinking we were settled in a R2.0 SLOP.Brisbane (YBBB) queried us when crossing into their sector if we were offset 3nm; correcting us back to a maximum of 2.0. We recognized the error and corrected it.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.