(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 - Unpublished Work - See title page for details.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 - Unpublished Work - See title page for details.  34-26-0 Page 15 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.

(2)  
The AUTO APP mode provides for automatic capture of the localizer and glide slope beams from other lateral or vertical modes. When switching to the AUTO APP mode from the VOR/LOC mode after localizer beam capture, the GS arm (amber) indicator illuminates at the annunciator if a "GS flag" signal is generated by the GS receiver and a "LOC freq" select signal is initiated by the VOR/LOC receiver. When the center of the glide slope beam is intercepted, a "GS capture" signal is generated in the GS beam sensor and the computer is automatically switched to the final approach phase. The COMPUTER warning flag at this time begins monitoring glide slope information in addition to its other inputs. At this time also, the GS (green) indicator illuminates in the annunciator.

(3)  
In the final approach phase, the bank channel utilizes the same signals as described for VOR/LOC mode and the roll commands are limited to 15 degrees. After glide slope capture the localizer deviation pointer comes into view in the HSI and indicates deviation from the localizer beam at approximately twice the sensitivity of the HSI bar. The complementary filter provides for cross wind correction. Its output is combined with the localizer deviation signal to provide a damping signal. The difference between these two signals becomes the bank command signal. The bank command signal is then mixed with the bank error signal to yield the bank steering command signal.
　
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：737 AMM 飛機維護手冊 導航 NAVIGATION 1(94)