Honeywell International Inc. DMA-37B2 Manuale Utente

Page 1001

10 Oct 2007

DMA-37B DME System

© Honeywell International Inc. Do not copy without express permission of Honeywell.

(1) Fault isolation is the process of isolating the source of a system failure to an LRU (line 

replaceable unit) or to the aircraft wiring.

(2) For the -1101 and -1212 units, the front panel display indicates the status of the unit. The 

top LED  shows the internal status and shows RED with an internal fault. The center LED 

is normally off and when displaying RED indicates an external failure with either the 

ARINC 429 inputs or unit strapping. The bottom LED shows RED if there is a problem 

with  the antenna connection. A separate connector on the units can be used with an 

adapter to show the indications and functionality described below with the LCD 

functions. The LEDs show amber during the self test function described in the following 

procedure.

(3) Fault isolation in the DMA-37B DME System includes a continuity check of the 

interwiring, and the assurance that proper installation techniques and procedures have 

been followed.

(4) A functional self test of the LRU can be initiated by pressing the test key pushbutton 

switch as designated on the front panel LCD, see Figure 1001. Although the 

normal-mode screen indicates that this actuated from the right key, the left key has the 

same function if pressed while the DMA-37B is in its normal mode.

(5) A complete functional test of the system can be performed as described in the 

MAINTENANCE PRACTICES section of this manual.

(6) Figure 1002 illustrates the control flow of the LCD screens (except for the data loading 

and data recording screens).