(2)
In the roll channel, course error, VOR or LOC deviation rate, and roll attitude are used to generate lateral steering commands. The course error signals from the control panel are proportional to the difference between the selected course and the actual airplane heading. The radio deviation signal from the navigation receiver is proportional to the angular displacement of the airplane from the selected VOR or LOC course. The bank attitude signal is generated by the attitude reference system. These signals are applied to the complementary filter. The output of the filter is a radio damping signal which opposes the VOR or LOC deviation signal in order to prevent overshoot in following the command. The radio damping signal is combined with the direct radio deviation signal. In the LOC mode, it is again combined with the direct course error signal. The resultant is applied to the course cut limiter. The action of the limiter is to prevent intercept of the selected course at fixed heading angles greater than 30 degrees. The signal is then passed thru the bank limiter and summed with the bank attitude signal. The result is a signal that is proportional to the difference between commanded bank and actual bank attitude. The resultant signal is amplified and converted to dc signal to become the bank steering command to the ADI.
(3)
At approximately 8 to 10 degrees from the VOR beam center, the computer will generate roll commands due to high gain radio rate signals. The V/L beam sensor is activated by V/L mode voltage with NAV FLAG, and VOR/LOC inputs. When the airplane is within 3 degrees of a selected VOR radial a "nav-capture" signal, generated at the V/L beam sensor, changes the course cut limiter output and reduces the command intercept angle from 30 to 20 degrees. At the same time however, differentiating circuits in the computer are producing a damping signal (radio rate) which initiates a bank command. If the airplane path follows the V-bar roll commands the resultant flight path will be a smooth flare-in to the course. At the same time, the "nav-capture" signal turns off the HDG V/L signal. This activates a timer which, after a minimum of 60 seconds delay on, provides a "track" signal provided that the bank angle is less than 3 degrees. When both of these criteria are met, the computer is latched into the track mode until another mode is selected. The output is provided to maintain "nav-capture" switching during temporary loss of a V/L beam sensor input and for gain switching in the computer.
(4)
When flying to a LOC course the point at which beam capture occurs varies with airplane speed. At higher airplane speeds, beam capture occurs farther from beam center to produce an earlier roll command and to prevent overshoot. At NAV capture, the course cut limiter angle is reduced from 30 to 20 degrees.
(5)
Pitch channel operation in this mode is identical to that in the HDG mode.
576
34-26-0 Page 14 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 15/79
576
Feb 15/79 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-26-0 Page 15
F. HDG V/L Arm Submode
(1)
The steering computer provides steering commands to the ADI in the HDG V/L submode which when flown by the pilot provide for the capture of a selected VOR or localizer beam from any selected heading which intersects the beam. This is different from VOR/LOC mode, where an intercept angle of 30 degrees is maintained by the course cut limiter. HDG V/L submode is engaged by turning the mode selector switch momentarily to the HDG position and then to the VOR/LOC position. When this is done, the amber VOR/LOC and the HDG SEL lights will come on at the annunciator, and the system operates initially as in HDG mode. Steering will be along the selected heading until the VOR or LOC deviation decreases to a level where the "nav-capture" signal is generated. When "nav-capture" is generated at the V/L beam sensor, the computer is automatically switched to either the VOR, or LOC mode of operation. The VOR/LOC annunciation changes from amber to green and the HDG light will turn off. At this time, the CMPTR warning flag will also begin monitoring VOR or LOC information from the navigation unit. Also, the computer will generate the TRACK signal at a minimum of 60 seconds after the "nav-capture" signal has occurred and when the bank angle becomes less than 3 degrees.
(2)
In this mode, pitch channel operation is the same as that described for HDG mode.
H. AUTO APP Mode
(1)
In the AUTO APP mode, the steering computer provides lateral and vertical steering information to the ADI which when followed by the pilot will enable him to maintain the airplane at the selected localizer course during final approach to the runway while holding to the glide slope path.
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：737 AMM 飞机维护手册 通讯描述和操作(118)
