5A5 
Feb 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-26-0 Page 17 

L12964
Glide Slope Time Base Gain Programming  5A5 
34-26-0  Figure 4  Feb 20/85 
Page 18 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

J.  GA Mode
(l)  The GA (Go-Around) mode of operation is used for an aborted approach. In the GA mode, when the pilot aligns the V-bars against the miniature airplane in the ADI, the real airplane will be in a wings level 14-degree pitchup climbout angle. When initiated, the roll channel commands wings level and the pitch channel commands a 14-degree pitchup angle to the ADI. The system will automatically switch to GA, from either of the glide slope modes, by depressing the go-around switch on the thrust lever. This energizes the switch release solenoid and permits the mode selector to spring back to the GA position. When the system is in the GA mode, the GO AROUND lights on the annunciator displays will be on and the computer produces steering commands in the bank and pitch channels. In the bank channel, the computer receives bank error signals from the attitude reference system which are directed to the ADI as bank steering commands. The V-bars indicate the corrections necessary to keep the airplane level in a lateral plane. In the pitch channel, the computer receives and mixes pitch error signals from the attitude reference system with the 14-degree pitchup bias to produce pitch steering command signals. These steering command signals are transmitted to the V-bars in the ADI.The V-bars then indicate the necessary corrections to keep the airplane in the desired flight path in respect to pitch.
K.  HDG-GA Mode
(l)  The HDG-GA mode enables the pilot to fly the airplane to and maintain a selected heading while maintaining the airplane at the fixed GA pitch-up command. When HDG mode is selected from the GA mode without stopping in OFF mode, the 14-degrees pitch up command is retained in the pitch channel. The fixed pitch-up command can be overridden by selecting ALT HOLD or another mode on the mode selector. In the roll channel, the system will provide commands to fly to the selected heading. In this mode, the ROLL GA signal is not generated thereby allowing the heading error signals to be added to the roll attitude signals and the roll steering commands generated as in the HDG mode.
L.  Altitude Hold Submode
(l)  The altitude hold submode can be used in HDG, VOR/LOC and AUTO APP modes. If the air data computer fails, a warning flag voltage switches off the CADC relay in the accessory box. This opens the altitude hold circuit and the ALTITUDE HOLD switch returns to the OFF position. In AUTO APP mode, as soon as glide slope capture is generated a transistor is turned off in the computer, opening the altitude hold solenoid circuit and the ALTITUDE HOLD switch springs to the OFF position. This enables glide slope deviation signals to be used in the pitch channel instead of pressure altitude deviation signals.
576 
Feb 15/79  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-26-0 Page 19 

M.  Computer Flag Circuit Operation
(1)  
Figure 5 shows a chart diagram of the computer flag circuit which provides a ground to operate the computer flag in the ADI. If the various inputs to the computer are correct and the computer is functioning properly, the computer switch will be on to complete the computer flag solenoid circuit and pull the COMPUTER flag out of view.

(2)  
The AND circuit in the ADI monitors the input DC voltage and the flag circuit signal from the computer. The switch monitors the servo error signal from the null detectors. If the null detector in either the roll or pitch channel detects more then 3 degrees of error between the command signal and the V-pointer position signal, the switch circuit will be off. Therefore, the switch to ground for the flag solenoid will be open allowing the CMPTR flag to come into view. In addition, if either the DC voltage fails or the flag circuit signal is not present, the AND circuit will be off and the flag solenoid will not operate allowing the CMPTR flag to come into view.

(3)  
The roll monitor and pitch monitor circuits in the computer comprise transistor/diode logic to monitor the various inputs. In the illustration, the input signals are read horizontally and the relevant inputs for a specific mode are read vertically. The "x" indicates that the signal voltage is present. For example, in the roll monitor block in VOR/LOC mode the input signals which are essential to complete the AND gate are PITCH MONITOR, NAV FLAG, ATTITUDE VALID, COMPASS MONITOR, HEADING POWER (28V-dc) and ATTITUDE POWER (38V-dc).

(4)  
The pitch monitor signal is produced in the pitch monitor circuit from various inputs, depending on the operating mode of the pitch channel which has been selected. If AUTO APP is selected, the computer will monitor the HDG inputs in the pitch monitor until the computer is switched by a glide slope capture voltage. In GS mode, although GS is selected, the computer will be in either MANUAL PITCH or ALT HOLD before G/S capture.
　
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