B777-200
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action
Company Policy; Weather
One hour into flight I was Relief Pilot in Bunk. We hit severe turbulence for 15 minutes followed by continuous MOD TURB. It lasted nearly 30-45 minutes. When my break was over I returned to cockpit. They told me they gained/ lost 100 FT and it set off the overspeed warning horn for 4-5 seconds. They did not know how much the VMO exceedance was because of the side to side and up down motion of the turbulence. Prior to flight the weather picture showed a severe blob of weather. But the flight plan has notes telling pilots to not even ask for [the normal alternate routing around] Mendoza valley then up the Pacific. The flight plan notes discourage pilots from even asking for [company specific alternate routing]. We are told in ground school it is only 100 miles difference. Yet the flight plan notes say that route costs $9K to 16;000 dollars more. I find that hard to believe.  Net result we scared a full flight of CUSTOMERS because some guy who sits at a desk and has never flown this route decided to write notes on the flight plan demanding that pilots disregard safety. Please look at the notes on the flight plan. Fleet CA 777/787 and some other guy wrote these notes DO NOT ASK DISPATCHER FOR [alternate routing].  This was the one time that if I'd been the CA I would have called and asked for [the alternate routing]. I know this sounds harsh; but I am a Captain in training. And things like safe flight planning must prevail. The pilots told me they deviated more than 100 NM around this weather and even that was not enough.
B777 Relief Pilot reports encountering severe turbulence while he is in the bunk. The area of severe turbulence was known prior to departure but the Dispatcher did not plan around it and the crew was discouraged from requesting a different route.