(b)  
When a system malfunctions, fault annunciators on the front of the receiver-transmitter will indicate which system component has failed. The annunciators are labeled IND (height indicator), R/T (receiver-transmitter), and VSWR (antennas and coaxial cables). The IND annunciator is inoperative on receiver-transmitter 3. The annunciators will change from a black to yellow display to indicate a component failure.

 EFFECTIVITY
 LH ALL; IB 405  CONFIG 4  01 Page 15  Apr 25/8834-33-00
 (c)  
The signal presence monitor monitors the return signal strength. When the level decreases below a predetermined level the circuit provides a warning output to the flag logic gate.

 (d)  
The VSWR monitor monitors the transmitter output power, receiver gain, and condition of the antennas and antenna cables. If any of the monitored parameters fall out of tolerance, a signal is sent to the flag logic gate.

 (e)  
The | 30 volt monitor monitors the output of the +30 volt and the -30 volt power supplies. If the output of either supply increases or decreases beyond specific limits, a warning output is supplied to the logic circuits.

 (f)  
The greater-than 2500 foot monitor indicates to the logic circuits whether the altitude signal frequency is above or below 115 kHz (2500 feet).

 (g)  
The dc altitude comparator monitors the two altitude output voltages from the operational amplifiers by comparing them. If the two voltages do not agree within 50 mv, an output is provided by the logic circuits.

 (h)  
The modulation monitor is used to monitor the transmitter modulation rate. A significant change in modulation rate will result in a warning output to the logic circuits.

 B. Control
 (1)  Turn on Procedure
 (a)  
Provide electrical power (Ref 24-22-00).

 (b)  
Provide equipment cooling air (Ref 21-58-00).

 (c)  
Close ALTM LOW R1 and ALTM LOW R2 circuit breakers on P7. On airplanes with three LRRA systems installed, close ALTM LOW R3 circuit breaker on circuit breaker panel P126.

 (d)  
The height indicators should display an altitude between -3 and -11 feet with the warning flag out of view. The LRRA-3 failure annunciator should display a valid (black) indication.

 EFFECTIVITY

 LH ALL; IB 405  CONFIG 4  01 Page 16  Apr 25/8834-33-00
 LRRA SYSTEM - TROUBLE SHOOTING
______________________________
 1.  General
_______
 A.  The following trouble shooting procedures are based on performance of the system operational test and are presented in tree-type format. The test steps (heavy-line boxes) are connected by shaded arrows to show the OK condition path. When all steps in the OK condition path check out, the system is operable.
 B.  When a test step does not check out, follow the NOT OK line to the box containing the trouble symptom. Turn to the procedure indicated and continue to follow a single line by analyzing the results of each test step until the required corrective action is determined. Perform the specified corrective action, then repeat the step at which the failure was encountered.
 C.  All trouble shooting procedures are based on the assumption that wiring is OK and that electrical power is available. If the corrective action in the procedure does not correct the problem, check wiring using the wiring diagram.
 D.  The trouble shooting procedures of par. 3 are for LRRA systems 1 and
 2. Use the captain's instruments and controls to check system No. 1 and the first officer's instruments and controls to check system No.
 2.
 E.  On AZ ALL, IB 406-499, a third LRRA system is installed. Paragraph 4 contains the trouble shooting procedures. System 3 contains no operating controls or altitude indicating units. A failure annunciator is provided on the pilots' center instrument panel P2.
 2.  Prepare for Trouble Shooting
____________________________
 A.  Check that ALTM LOW R1 and R2 circuit breakers on overhead circuit breaker panel P7 are closed.
 B.  AZ ALL, IB 406-499, check that circuit breaker ALTM LOW R3 on circuit breaker panel P126 is closed.
 C.  Provide electrical power (Ref 24-22-00, Maintenance Practices [Apply Power]).
 D.  Operate equipment cooling system (Ref 21-58-00, Adjustment/Test
 [Operational Test]).

 EFFECTIVITY

 AZ ALL; IB 406-499  CONFIG 1  03 Page 101  Apr 25/8834-33-00
3. _______________________
LRRA Systems No. 1 or 2
T34431
..XA
Prepare system for trouble shooting as described in par. 2. Observe height indi-cator indicates between -3 and -11 feet and warning flag is out of view. IF -
　
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