B777-200
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Diverted
Aircraft; Human Factors
Noticed slight airframe vibration in the climb.   At FL300 it was much worse. Getting even more vibration as speed increased.  Called up the flight control page and saw the R FLPRN was almost all the way up with the L in a normal position.  The control column was 2 degrees right wing down.  Called Operations Control and discussed.  Had the Tech Pilot on the phone also.  All agreed it was not normal.  Decision was to return to ZZZ.  Had to dump fuel.  Did this in coordination with Center.  Arrival was normal until landing flaps were selected.  When flaps started past 20 the airplane shook violently and rolled to the R.  Re-selected flaps to 25 and added 15 knots.  At the gate the maintenance tech could see the Number 6 spoiler was up.  Wrote up the discrepancies and debriefed the mechanic.  Crew did a phenomenal job.  Great back up.Cause - Spoiler float not locked down.
Aircraft X did a block turn back for a spoiler issues when I first sat down.  After nearly 5 hours on the ground; we received a duty extension and the flight departed. (XA16z) At approximately XA55z crew sent ACARS message:...ALT AIRFRAME VIBL ENG 1.0  R ENG .9R FLPRN IS UPVIBWORSE AT HIGHER SPD.I spoke with the crew on the SATCOM for over an hour bringing in Operations; Tech Pilot; Maintenance Control and Maintenance Control talked to mechanics that did the spoiler work.  We determined it was odd behavior for B777 controls and this aircraft usually flies straight. Determination was made to bring the flight back to ZZZ as this may not be an easy fix.
B777 flight crew and the flight Dispatcher reported airframe vibrations during climbout which worsened as the speed increased.  The crew contacted the company and decided to return to their departure airport.  Reportedly; the cause of the issue was a spoiler float was not locked down.