TM 1–1520–238–T–3
20–1
CHAPTER 20
DOPPLER MULTIPLEX READ CODES
Doppler uses two words to provide data. The Doppler words are read with bit 19 being the most significant bit and
bit 4 being the least significant bit. The analog MEMORY LOCATION will have both memory inspection locations
listed.
19
18
17
16
15
14
13
12
11
10
9
8
7
6
6
4
MSB
LSB
EXAMPLE:
20–7 SIGNAL NAME:
DOP DRIFT VEL 1
MEMORY LOCATION: 000451 AND 000452
MEMORY DATA BIT(S):
16–4 AND 19–18
(SCALAR)
CONDITION:
Monitor HOD digits 6, 5, 4, 3, and 2 should read 0
SIGNAL FUNCTION:
Indicated doppler drift velocity.
REMARKS: From doppler through copilot/gunner (CPG) multiplex remote terminal unit
(MRTU) Type III to fire control computer (FCC).
PASS:
If CONDITION agrees with drift go to paragraph 20–8.
FAIL: Location of fault: Doppler, wiring from Doppler to CPG MRTU Type III, CPG
MRTU Type III. Troubleshoot wiring to isolate fault (TM 11–1520–238–23–2).
FAILURE SYMPTOM INDEX
Symptom
Refer to paragraph
CDU DOES NOT DISPLAY CDU/DNS GO AND CURRENT VALUES . . . . . . .
20–1
INACCURATE DRIFT (ASN–137 SDCC A/D FAIL) . . . . . . . . . . . . . . . . . . . . . . .
20–1
INACCURATE PITCH (ASN–137 PITCH/ROLL FAIL) . . . . . . . . . . . . . . . . . . . . .
20–21
NO TRACK ANGLE ERROR OR GROUNDSPEED . . . . . . . . . . . . . . . . . . . . . . .
20–28
INACCURATE ROLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–33
INACCURATE DESIRED TRACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–35
INACCURATE CROSS TRACK DEVIATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–42
INACCURATE DISTANCE TO GO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–49
INACCURATE BEARING TO DESTINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–55
INACCURATE 100 KM SQUARE IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . .
20–55
INACCURATE HEADING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–55
INACCURATE VELOCITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–55
HDG OR A.C. REF FAIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20–80
