S 864-092
(3)
Set the No. 1 and 2 switches of the STAB TRIM hydraulic to the AUTO position. The switches are on the Pilots' Control Stand.
S 744-081
(4)
Do this task: Ground Test - Elevator Servo (Ref 22-10-00/501).
(a)
Push the LSK that is adjacent to <SERVO-ELEVATOR.
(b)
Make sure that no fault messages show.
(c)
Continue with the instructions shown on the CDU until this message shows:
ENGAGE AUTOPILOT L C R
TO CMD POSITION
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A 747-400 MAINTENANCE MANUAL
(d) Push the applicable autopilot CMD (L, C, or R) button on the Mode Control Panel.
NOTE:____ The left EAS is connected to the left FCC. The center EAS is connected to the center FCC. The right EAS is connected to the right EAS.
(e) (f) Push the LSK that is adjacent to <CONTINUE.Make sure that no fault message shows for the cannel that you engage.
NOTE:____ Fault messages (ENGAGE FAIL) shown for the other channels that you did not engage are permitted.
(g) (h) Continue with the instructions on the CDU to complete the test.Make sure that the SERVO-ELEVATOR test is completed with no failure for the applicable FCC.
NOTE:____ An autopilot disconnect warning will occur at the end of this test, which is permitted.
(i) Push the captain's or first officer's autopilot disconnect switch two times.
(5) S 864-082Remove hydraulic power (Ref 29-11-00/201).
(6) S 794-083Visually examine the valves and make sure that there are no hydraulic leaks.
(7) S 414-084Close the 315A access door in the tail cone (Ref 06-09-05/201).
(8) S 794-085Remove electrical power if it is not necessary (Ref 24-22-00/201).
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747-400 MAINTENANCE MANUAL
AUTOPILOT/FLIGHT DIRECTOR ROLL AND YAW AXIS CONTROL -
___________________________________________________ DESCRIPTION AND OPERATION
_________________________
1. General_______
A. This section describes the details of autopilot control of the roll and yaw axis of the airplane. Before an A/P channel is engaged through the MCP, there is a sequence of events that occurs to insure the reliability of the channel and a smooth transition to autopilot control of the airplane. Each FCC controls the roll axis through one of two Central Lateral Control Packages (CLCPs) and one Lateral Autopilt Servo (LAS).
B. The locations of the roll and yaw axis control components are shown in Figure 1.
C. The CLCPs and LAS perform the same function; they accept electrical A/P commands, and by transfering hydraulic fluid to either side of internal actuators, produce mechanical outputs to the aileron programmers and spoiler differential mechanisms. The CLCPs differ from the LAS in that they accept mechanical inputs from the control wheel to control the airplane during manual operation (Ref 27-00-00/001).
D. Autopilot control of the yaw axis is through three Rollout Power Control Packages (RPCPs). The servo function is very similar to the CLCPs and LAS. The autopilot control of the yaw axis is active only during triple channel A/P engaged autoland and rollout.
E. The RPCPs control the rudders to align the airplane with the runway centerline prior to touchdown, also to provide high speed rollout steering and low speed rollout control through linkages to nose gear steering.
F. The A/P modes that provide commands to the roll axis are: LNAV mode, which provides horizontal steering commands from the FMC; LOC and APP modes, which develop commands to capture lacalizer and track the localizer centerline; HDG SEL, used to turn the airplane to a heading selected on the MCP; HDG HLD is the basic roll mode that holds the airplane heading at the time of engagement.
G. The yaw axis is controlled only during APP mode for runway alignment and ROLLOUT mode after touchdown. Mode engagement, and acceptible mode transitions are contained in 22-10-00/001.
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