777 AIRCRAFT MAINTENANCE MANUAL
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SPOILER AND SPEEDBRAKE CONTROL -FUNCTIONAL DESCRIPTION -NORMAL MODE
General
In the normal mode operation of the PFCS, the PFCs calculate spoiler commands from this information:
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Spoiler roll schedules
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Spoiler lockout logic
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Spoiler speedbrake schedules
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Mechanical speedbrake logic
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Speedbrake inhibit logic
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Spoiler mixing
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Autopilot roll commands.
Spoiler Roll Schedules
The PFCs receive roll control command signals from the wheel position transducers and from the autopilot. The spoiler roll schedules calculate the roll commands for the inboard and outboard spoilers. There are three different schedules. To select the applicable schedule, the PFCs use this information:
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Spoiler number (1 to 14)
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Flap position
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Spoiler lockout logic.
In roll control, the PFCs command the inboard spoilers to a maximum of 20 degrees and the outboard spoilers to a maximum of 45 degrees.
EFFECTIVITY BEJ ALL
The cable-controlled system and linkages supply fixed roll schedule for spoilers 4 and 11 to move to a maximum of 45 degrees.
Spoiler Lockout Logic
The spoiler lockout logic affects the roll commands of spoilers 5 and 10. The PFCs use computed airspeed (CAS) and altitude data from the ADIRUs to calculate when to lockout these spoilers. The PFC commands cause spoilers 5 and 10 to fair to the wing surface and to lock out at cruise speed. The PFCs use the same lockout logic for aileron lockout.
Spoiler Speedbrake Schedules
The PFCs receive speedbrake control command signals from the speedbrake lever position transducers. The PFCs use spoiler speedbrake schedules to calculate the speedbrake commands for all spoilers, except 4 and 11. There are four different schedules. To select the applicable schedule, the PFCs use the spoiler number (1 to 14) and the main landing gear (MLG) on ground status.
During speedbrake control in flight, the PFCs command the inboard spoilers to a maximum of 15 degrees and the outboard spoilers to 45 degrees, except for spoilers 4, 5, 10, and 11. Spoilers 5 and 10 do not operate as speedbrakes in flight. Spoilers 4 and 11 operation is described in the paragraph below about mechanical speedbrake logic.
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SPOILER AND SPEEDBRAKE CONTROL -FUNCTIONAL DESCRIPTION -NORMAL MODE
During speedbrake control on the ground, the PFCs command all the spoilers, except spoilers 4 and 11, to move to a maximum of 60 degrees.
Speedbrake Inhibit Function
The speedbrake inhibit function has an effect on the ground spoiler speedbrake commands. The function receives main landing gear on the ground signal from the PSEU and the pitch attitude from the ADIRU. The function also monitors the position of the speedbrake lever.
The speedbrake inhibit function operates when the pitch attitude is more than 2 degrees with the airplane on the ground or during the first 1.25 seconds after a main landing gear air to ground transition. When there is a speedbrake lever command, the outboard spoilers 2, 5, 10 and 13 do not deploy. The PFCs limit the inboard spoilers 6, 7, 8, and 9 to 20 degrees until the speedbrake inhibit function is no longer active.
Mechanical Speedbrake Logic
The mechanical speedbrake logic affects spoilers 4 and 11. The PFCs do not use speedbrake schedules for these spoilers. When the speedbrake lever position transducers indicate a command greater than 54 degrees, the PFCs cause the PCU speedbrake solenoid to energize. The PCUs for spoilers 4 and 11 then extend to move the spoilers to 45 degrees.
Spoiler Mixing
The PFC spoiler mixing function combines the roll and speedbrake commands into one mixed command for each electrically-controlled spoiler. This combines the roll commands from the control wheels with the speedbrake commands from the speedbrake lever.
For spoilers 4 and 11, there is no mixing of roll and speedbrake commands. Roll commands go through the cable-controlled system. The PFCs send only the speedbrake commands. The speedbrake function has priority over the roll function for spoilers 4 and 11. No matter what the roll command is, the PFCs extend spoilers 4 and 11 to 45 degrees TEU when the pilots move the speedbrake lever past 54 degrees.
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SPOILER AND SPEEDBRAKE CONTROL -FUNCTIONAL DESCRIPTION -NORMAL MODE
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