(b)
The inner loops provide processing of signals that are required in all modes of operation. These are also subdivided before going into the common output section. The input commands from the cruise outer loops are combined with pitch attitude and attitude rate before common processing. The approach modes are based on rate of descent or climb and do not use the pitch attitude as a prime guidance input.
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(c) The inputs of the inner loops are combined and after conversion to analog are fed to the valve (servo) amplifier. This provides the output to the elevator A/P actuator which provides a mechanically coupled input to the elevator power control units to move the elevator. Position feedback is provided from the A/P actuator (LVDT) and from the elevator position sensor.
(5)
The Flight Director system has separate sections for handling the cruise commands, TO/GA, and the approach. These are selected prior to the D/A converter and sent to the ADI pitch command bar.
(6)
The pitch channel also provides outputs to the stabilizer for maintaining proper pitch attitude. A combination of stabilizer position and elevator output command is used to determine when the stabilizer should be repositioned. The output to the mach trim actuator is used to reposition the elevators as a function of mach number. This is accomplilshed by mechanical connections to the elevator feel and centering unit and the Neutral Shift Sensor (NSS). The NSS, in turn, provides an electrical input which is fed through the servo amplifier to the A/P actuators.
(7)
The mode logic and selection section provides outputs to the flight mode annunciator to visually display the pitch channel status.
P. Pitch Axis Analog Interface (Fig. 30)
(1)
The Analog Interface diagram illustrates the various LRU's which are associated with the generation and implementation of logic and command signals used using pitch axis modes of operation. All of the signals are converted from analog to digital for inputs and digital to analog for outputs.
(2)
The following is a breakdown of the various inputs and their relationship to pitch axis operation.
(a)
Cross channel disconnect B is a 28 volt dc logic signal to inform one channel that the other has disengaged.
(b)
The pitch equalization signal is used as a comparison between Elevator Actuator A and B feedback for dual autoland operation.
(c)
The Test Sync B signal is used during BITE testing to indicate that both FCC's are installed.
(d)
The angle of airflow input is used primarily during takeoff and go around modes. It provides a reference to prevent the airplane from reaching stall conditions.
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ENGAGE INTLK DC
FCCA-DC
FCC A ENGA DC
M980 AUTO SPEED BRAKE MOD (E3-2) M924 FLIGHT CONTROL COMPUTER A (E1-3) Pitch Axis Analog Interface Block DiagramFigure 30 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737-300 400 500 AMM 飞机维护手册 自动飞行 AUTOFLIGHT 1(41)
