Message Name:

DISTANCE MEASURING EQUIPMENT (DME) SYSTEM NO DATA

The Distance Measuring Equipment (DME) System cannot receive guidance data.

• Distance Measuring Equipment (DME) Radio Module
• Very High Frequency (VHF) Navigation Unit 1 (A3)
• Very High Frequency (VHF) Navigation Unit 2 (A4)
• Distance Measuring Equipment (DME) Antenna 1 (Bottom) (E7)
• Distance Measuring Equipment (DME) Antenna 2 (Bottom) (E6)
• Distance Measuring Equipment (DME) 1 In-Line Filter (FL3)
• Distance Measuring Equipment (DME) 2 In-Line Filter (FL4)

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: The optional VHF NAV unit 3 does not contain a DME radio module.

NOTE: When the radio system is initially energized (after a cold-start and during a WOW condition), it automatically starts the POST. The POST does an RMU test, RSB continuity test, and radio module test. The POST does not do a test of the antennas, in-line filters, diplexers, or coaxial cables.

1. If the RMU display shows CHK NAV 1-2 UNIT, push the TST (test) pushbutton on the RMU to get the RADIO TEST RESULTS page from the SYSTEM TEST RESULTS page. Check if the RMU display shows DME 1-2 ERR.
   NOTE: If the RMU display shows CHK RMU 1-2, or, if the RMU displays are magenta, perform the troubleshooting for radio management units.

   1. If the RMU display does not show DME 1-2 ERR, go to step 3.
   2. If the RMU display shows DME 1-2 ERR, continue with next step.

2. Perform the operational test of the RSB part of the digital bus system. On the CAIMS PMAT, perform the IBIT of the RSB part of the digital bus system.

   1. If the results of the RSB test are not satisfactory, repair or replace the defective RSB wiring as required and do close out.
   2. If the results of the RSB test are satisfactory, continue with next step.

3. On the RMU display, look on the applicable maintenance log page(s) for the messages that follows:

   Event Description	Maintenance Page (Radio or cluster module)	Event Code
   CODE ERR	Cluster	A5
   COMPUTER	Cluster	06, 07, 08, 09, 86, 87, 88, 89, A4
   COMPUTER	Radio	06, 07, 08, 09, 25, 26, 86, 87, 88, 89, 2A, 2B, 2C, 2D, AA, AB, AC, AD
   DATA BUS	Cluster, Radio	03, 04, 05, 83, 84, 85
   DME DATA	Radio	2E, 2F, AE, AF
   DME RCVR	Radio	30, B0
   DME TUNE	Radio	27, 28, A7, A8
   FPGA ERR	Cluster	B0
   OVERHEAT	Radio	26, A6
   PWR SUPPLY	Radio	21, 22, 23, 24, 25, A1, A2, A3, A4, A5
   RAM ERR	Cluster	A1, A2, A3, 2A
   RSB PRI	Cluster	AB
   RSB SEC	Cluster	AC
   RSB TX	Cluster	AD, AE
   STRAPS	Cluster	A6

   1. If the messages are not found, do close out.
   2. If one or more of the given messages are found, replace the VHF NAV unit 1-2 and continue with next step.

4. On the RMU display, look on the applicable maintenance log page for the message as follows:

   Event Description	Maintenance Page (Radio or cluster module)	Event Code
   DME XMTR	Radio	29, A9

   1. If the given message is not found, do close out.
   2. If the given message is found, continue with next step.

5. Perform a visual inspection of the DME system components and related coaxial cables.

   1. If the defective components are not found, do close out.
   2. If the defective components are found, continue with next step.

6. Replace the defective DME antennas, defective DME in-line filters and defective coaxial cable.
7. Do close out.