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MAINTENANCE MANUAL
(d)
LOC Two-Turn Capture
1) When conditions cause LOC2TC to be logic 1, P2TURN is selected for processing. Since P2TURN has been continuously computed during LOC mode arm, LOC prop roll assumes the value of P2TURN at LOC CAPT and is maintained at that value during the turn towards the beam. System response downstream from this summing point is the same as during P1TURN operation. When LOC2TC conditions no longer exist due to increased DGTRK, P1TURN is selected for the second capture turn.
(e)
LOC Linear Conditions
1) Final capture criteria is determined by the need to minimize overshoot and to avoid excessive rolldown rates. Continuous computation of lateral deviation and deviation rate occurs during the initial capture turn established by LOC proportional roll command. The LOCLIN logic is generated after LOCCAPT when LOC deviation rate is within the capture band in the LOC CMD processor filter frequency computation. The maximum rolldown rate command is P2MAX. When computations detect that rolldown rate equals P2MAX, the LOCLIN transition occurs and establishes filter values in the LOC CMD processor.
2) Localizer command integrator already has an output derived from cross runway acceleration command during the initial capture turn. This is now modified at the summing point and fed back to the integrator. This output is of opposite sign to the original input, so it causes a rundown of the integrator output. This establishes a maximum DYC at LOCLIN initiation.
3) The LOC displacement error (DYE) which reduces as DYLOCF feedback reduces, is converted into a proportional roll command and summed with LOC displacement rate error to modify PCLOC as a function of DYLOCF. The gain schedule generates a dependent LOC integral command which eliminates any standoff error.
(f) Final Capture of LOC Centerline
1) The final capture flight path follows an exponented law. When the computed rolldown command is less than P2MAX, a new value is generated to control the final rolldown command.
(22) Autoland Mode - Roll and Yaw (Fig. 17)
(a) The MCP controls and displays related to the Autoland Mode are identified on figure 17.
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(c)
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MAINTENANCE MANUAL
The selected heading display shows the selected runway heading from the ILS control panel after LOC capture and maintains this display until the A/P is disconnected after landing or after the roll go-around mode is terminated. The B/A limit selector is usually left in the NORM position during autoland. When pressed, the approach mode switch/light (APP) initiates the transition into the autoland configuration. The other two engage switches are armed after the APP mode request has been accepted by the FCC. The other two engage switches can then be manually positioned to CMD and the FCC provides a logic out to hold the switches in CMD. This arms the multi-channel engage logic in the corresponding FCC pitch and roll channels.Autoland Roll/Yaw Flight Path 1) Four conditions of rollout control are shown: rollout arm,
rollout engage, rollout directional control engage, and
runway centerline guidance.Rollout Arm (A) 1) Rollout arm is single channel in CMD with APP selected.
The EADI displays LOC as the roll engaged mode. The A/P directional CMD is synchronized to rudder position. All non-engaged channels synchronize in roll and yaw.
Rollout Engage (B)
1) All channels are CMDENG in roll, pitch and yaw. The EADI displays rollout white as the roll armed mode. The A/P directional CMD and runway alignment command are active. Heading reference is to adjusted runway heading. Primary control is to track centerline using forward slip to hold the LOC centerline.
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