TM 1–1520–238–T–3
Change 4
13–3
13–4 SIGNAL NAME:
SCU 2 BITE VALID (ACY) FWD SCU BIT OK (ACZ)
MEMORY LOCATION: 002130
MEMORY DATA BIT(S):
8
(BINARY)
CONDITION:
(None)
SIGNAL FUNCTION:
Indicates if SCU 2 has failed.
REMARKS: From SCU 2 through DASEC to FCC.
PASS:
If fourth digit on HOD is 4, 5, 6, or 7, go to paragraph 13–5.
FAIL: Location of fault: SCU 2, wiring from SCU 2 to DASEC, DASEC. Troubleshoot wiring to isolate
fault (TM 1–1520–238–T–7).
13–5 SIGNAL NAME:
SCU 2 STATUS (ACY) FWD SCU STAT (ACZ)
MEMORY LOCATION: 002130
MEMORY DATA BIT(S):
7
(BINARY)
CONDITION:
(None)
SIGNAL FUNCTION:
Generates NO–GO message.
REMARKS: From SCU 2 through DASEC to FCC.
PASS:
If fifth digit on HOD is 1, 3, 5, or 7, go to paragraph 13–6 (ACY) or 13–5A (ACZ).
FAIL: Location of fault: SCU 2, wiring from SCU 2 to DASEC, DASEC. Troubleshoot wiring to isolate
fault (TM 1–1520–238–T–7).
13–5A SIGNAL NAME:
FWD SCU GND REF (ACZ)
MEMORY LOCATION: 002130
MEMORY DATA BIT(S):
12
(BINARY)
CONDITION:
Should always be zero
SIGNAL FUNCTION:
Generates NO–GO message.
REMARKS: From SCU 2 through DASEC to FCC.
PASS:
If third digit on HOD is 0 or 4, go to paragraph 13–6.
FAIL: Location of fault: SCU 2, wiring from SCU 2 to DASEC, DASEC. Troubleshoot wiring to isolate
fault (TM 1–1520–238–T–7).
13–6 SIGNAL NAME:
STAB RATE GYRO 1 (ACY) STAB RATEGYRO LT (ACZ)
MEMORY LOCATION: 002124
MEMORY DATA BIT(S):
4–19 (ACY) 4–15 (ACZ)
(SCALAR)
CONDITION:
Monitor HOD while gyro is spinning up; memory location response digits should
decrease. Note reading.
SIGNAL FUNCTION:
Indicates axis position.
REMARKS: From rate gyro 1 to SCU 1, SCU 1 through DASEC to FCC.
PASS:
If the sixth digit displayed on the HOD is 0, compare reading from 13–1; if reading is equal, go
to paragraph 13–7.
FAIL: Location of fault: rate gyro 1, wiring from rate gyro 1 to SCU 1, SCU 1, wiring from SCU 1 to
DASEC, DASEC. Troubleshoot wiring to isolate fault (TM 1–1520–238–T–7).
13–7 SIGNAL NAME:
STAB AIRSPEED TRANSDUCER 1 (ACY) STAB AIRSPEED RT (ACZ)
MEMORY LOCATION: 002123
MEMORY DATA BIT(S):
4–19 (ACY) 4–15 (ACZ)
(SCALAR)
CONDITION:
Reading on HOD should be 0154200 or greater. Note reading.
SIGNAL FUNCTION:
Indicates 30, 60, 80 KT transition levels.
REMARKS: From airspeed transducer 1 to SCU 1, SCU 1 through DASEC to FCC.
PASS:
If the CONDITION corresponds to the memory location response, compare reading from
13–2; if reading is equal, go to paragraph 13–8.
FAIL: Location of fault: airspeed transducer 1, wiring from airspeed transducer 1 to SCU 1, SCU 1,
wiring from SCU 1 to DASEC, DASEC. Troubleshoot wiring to isolate fault
(TM 1–1520–238–T–7).
