B777 First Officer reported a track deviation occurred on their oceanic route when they deviated left of course to try to avoid wake turbulence; when only a right deviation was allowed.
Synopsis
B777 First Officer reported a track deviation occurred on their oceanic route when they deviated left of course to try to avoid wake turbulence; when only a right deviation was allowed.
Narrative
Description: Established SLOP (Strategic Lateral Offset Procedure) 1NM left of course between PUTER AND POXED while at FL350. Aircraft Y slowly passed 1000' directly overhead; with very clear engine exhaust contrails spun by wing vortices. Sky clear; winds direct cross from left to right at 10 - 21 knots. Persistent wake turbulence on track; looked like wake was going to be worse on track and right of track due to crosswind. Asked RJCC for climb; denied. Discussed it with other FO and elected to SLOP Left 1NM. When CA came up after rest period; he informed us of FOM requirement to only SLOP right of track. Canceled SLOP. Looked up reference; while now back in turbs; selected SLOP 1 NM right of track. Once preceding aircraft exceeded 40nm; was cleared to climb out of turbs.Cause: Unknown line item in FOM.Suggestions: Add note in FOM; that says 'SLOP right of course ONLY'.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.