There is one spoiler that isn't totally deployed. Look:
Source: Airliners.net
And also on this other picture:
Source: Airliners.net
Why aren't they deployed at the same angle?
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2 Answers
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Roll control is provided by 2 flaperons, 2 ailerons, and 14 spoilers.
Spoiler panels 4 and 11 are controlled mechanically rather than electrically. They are driven directly from control wheel deflections via a control cable. In case of compete electrical loss, limited roll control is available until the electrical system is restored. This probably explains the difference in rigging.
Spoiler panels 4 and 11 are also used as speedbrakes, both in the air and on the ground. The speedbrake function for this spoiler pair only has two positions: stowed and fully extended. The speedbrake commands for spoilers 4 and 11 are electrical in nature, with an ACE (actuator control electronics) giving an extend or retract command to a solenoid operated valve in each of the actuators.
Once that spoiler pair has been deployed by a speedbrake command, there is no control wheel speedbrake command mixing, as there is on all the other fly-by-wire spoiler surfaces.
Boeing B-777: Fly-ByWire Flight Controls
answered Apr 1, 2016 at 22:57
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7$\begingroup$ Follow-up question: Why are spoilers, rather than ailerons, used as the mechanical backup controls? $\endgroup$ Commented Apr 2, 2016 at 19:30
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In roll control, all spoilers except for 4 and 11, are fly-by-wire. Spoilers 4 and 11 receive mechanical signals for roll control. For spoilers 4 and 11, a cable system connects the control wheels to the spoiler PCUs. Cable movement supplies a mechanical input to the PCUs which move the spoilers. The movement of the PCU housing supplies mechanical position feedback.
In speedbrake control, all spoilers are fly-by-wire, including spoilers 4 and 11. For spoilers 4 and 11, speedbrake control is only available in normal mode. When the pilot moves the speedbrake lever more than 54 degrees, the PFC commands the ACE to send an ON/ OFF electrical signal to the two spoiler PCUs.
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3$\begingroup$ Am I missing something that differentiates this answer from the previously accepted answer? It seems very similar, and the post would probably be better served by editing the accepted answer to provide additional context. $\endgroup$– zymhanCommented Aug 16, 2019 at 15:55