(15)
The height indicator flag control circuit functions as a monitor of the servo loop, the ac voltage from the power supply, the flag alarm voltage, and the +30-volt dc reference voltage. When the signals applied to the null detector differ by more than the predetermined value, or if any of the other inputs to the flag control circuit are missing, the flag solenoid is de-energized and the warning flag comes into view.

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34-48-03 Page 6  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 15/79 

B.  Self-Test Operation
(1)  
Self-test of the LRRA system can be initiated at either captain’s or first officer’s height indicator. Relays and mode logic in the automatic flight control system (AFCS) accessory box control the LRRA self-test circuits. The circuits for LRRA-1 are controlled by the AFCS A channel and the circuits for LRRA-2 are controlled by the AFCS B channel. The appropriate LRRA self-test is inhibited when the AFCS A or B channel is engaged; the approach mode has been selected; and one of the following logics is present: LOC arm, LOC engage, GS arm, or GS engage.

(2)  
During self-test, a bias signal is applied to the isolators in the receiver-transmitter which causes the transmit signal to be routed through the delay line to the receive isolator. The signal is applied to the mixer and processed as a normal altitude signal. The test altitude is determined by the electrical length of the delay line. During self-test, the height indicators should display the test altitude.

(3)  
Self-test of the LRRA system can also be initiated by depressing the TEST/STATUS switch/lamp on the receiver-transmitter. This switch performs the same function as the test button on each height indicator. The STATUS lamp lights to indicate a successful test.

5C5
Oct 20/83 34-48-03 Page 7
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

LOW RANGE RADIO ALTIMETER SYSTEM - TROUBLE SHOOTING
EFFECTIVITY
GJ   B-2509, B-2510

1.  General
A.  If a malfunction occurs in the radio altimeter system the defective component should be replaced with a component known to be in good operating condition. Excluding the malfunctions listed below in par. B., substitutions should always be in the following order.
(l)  
If system is malfunctioning replace receiver transmitter with one known to be in good operating condition.

(2)  
Perform operational check system. If the system is still malfunctioning, replace height indicator.

(3)  
If system still malfunctions, inspect antennas for damage, airplane wiring and all connectors for improper connections or damaged items.

B.  The following malfunctions are directly traceable to the height indicator. If the system operation is normal and one or more of the following malfunctions occur, do not replace the receiver-transmitter first. Instead, replace the height indicator and check its wiring. If not ok, replace applicable receiver-transmitter.
(1)  
Dial lighting

(2)  
DH light

(3)  
Self-test pushbutton or DH control knob/cursor (all malfunctions)

(4)  
Flag not visible when circuit breaker is pulled

C.  DH light on ADI's can be tested for failed lamp by pressing light face.
5C8
Oct 20/85 34-48-03 Page 101
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

LOW RANGE RADIO ALTIMETER SYSTEM - ADJUSTMENT/TEST
EFFECTIVITY
GZ  B-2509, B-2510

1.  Low Range Radio Altimeter System Test
A.  Prepare to Test Low Range Radio Altimeter System
(1)  
Provide electrical power.

(2)  
Check that RADIO ALTM-1 circuit breaker on panel P18 and RADIO ALTM-2 circuit breaker on panel P6 are closed.

B.  Test Low Range Radio Altimeter System
(1)  
At both height indicators, set DH cursor to between -15 and -20 feet and check that:

(a)  
All DH lights are extinguished.

(b)  
Altitude pointer on both height indicators indicates between 0 and -10 feet.

(c)  
Warning flag on both height indicators is out of view.

(2)  
At captain's height indicator, depress self-test button and check that:

(a)  
Captain's DH light is extinguished.

(b)  
Altitude pointer on captain's height indicator indicates 40 +5 feet.

(c)  
Warning flag on height indicator is in view.

(3)
Release PUSH TO TEST button on the captain's height indicator and check that:

(a)  
Captain's DH light is extinguished.
　
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