Different True Airspeed Indication between CAPT ND and F/O ND

TASK 34-13-81-810-821-A
Different True Airspeed Indication between CAPT ND and F/O ND

1. Possible Causes

SENSOR-TAT, 1 [11FP1]
aircraft wiring
SENSOR-TAT, 2 [11FP2]
ADIRU-1 [1FP1]
ADIRU-2 [1FP2]
ADIRU-3 [1FP3]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 34-13-00-810-998-A	Altitude or Airspeed Discrepancy between CAPT PFD - F/O PFD - STDBY/ISIS
TSM TASK 34-13-00-810-998-B	Altitude or Airspeed Disagree between the CAPT PFD or F/O PFD and Standby Horizon Indicator or ISIS (Aircraft with RVSM capability on the three ADIRUs)
AMM 34-10-00-170-001	Flushing of the Principal Total Pressure Lines
AMM 34-10-00-170-002	Flushing of the Principal Static Pressure Lines
AMM 34-10-00-170-003	Draining and Flushing of Standby Pneumatic Circuits
ASM 341102
AMM 34-11-18-000-001	Removal of the TAT Sensor
AMM 34-11-18-400-001	Installation of the TAT Sensor
AMM 34-12-34-000-001	Removal of the ADIRU
AMM 34-12-34-400-001	Installation of the ADIRU
AMM 34-13-00-720-009	Functional Test of the Altitude and Airspeed Data (A/C without RVSM capability on ADIRU 3)
AMM 34-22-25-170-001	Draining and Flushing of the Standby Static and Standby Total Pressure lines (ISIS)

3. Fault Confirmation
Subtask 34-13-81-700-054-A

A. Test
Not applicable, you cannot confirm this fault on the ground.

4. Fault Isolation
Subtask 34-13-81-810-071-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the observation that follows:
Different true airspeed indication between CAPT and F/O ND:

do the flushing of the principal Total pressure lines AMM 34-10-00-170-001
do the flushing of the principal Static pressure lines AMM 34-10-00-170-002
if system 3 is affected, do the draining and flushing of the Standby Pneumatic circuits AMM 34-10-00-170-003
do the functional test of the altitude and airspeed data AMM 34-13-00-720-009.

(1) If the test gives a different altitude value and/or a different airspeed value from the ADR1 (compared to the ADR2 and the ADR3), from the ADR2 (compared to the ADR1 and the ADR3) or from the ADR3 (compared to the ADR1 and the ADR2):

do the trouble shooting procedure that follows (fault isolation only) (Ref. TSM TASK 34-13-00-810-998).

(2) If the test is OK:

make sure that the scoop and the choke of the TAT sensor 1 and TAT sensor 2 are not clogged or dirty.

(a) If the scoop or the choke of one TAT sensor is damaged:

repair the defective TAT sensor.

(b) If the scoop and the choke of the TAT sensors are not damaged:

disconnect the electrical connector of the TAT sensor 1
do a check of the resistance between pins A/E and J and pins A/H and K of the TAT sensor 1.

1 If the resistance value between pins A/E and J and/or pins A/H and K is not correct:

NOTE: The resistance value of the TAT sensors is:

500 ohms (plus or minus 0.2 ohm) at 0 deg.C (32 deg.F)
538.87 ohms (plus or minus 0.2 ohm) at 20 deg.C (60 deg.F).

replace the SENSOR-TAT, 1 [11FP1] AMM 34-11-18-000-001 and AMM 34-11-18-400-001.

2 If the resistance value between pins A/E and J and/or pins A/H and K is correct (Ref. NOTE above):

shunt pins A/E and J of the electrical connector of the TAT sensor 1
remove the ADIRU1 AMM 34-12-34-000-001
do a check of the resistance (R=1.04 ohm plus or minus 0.25 ohm) between pins AA/8H and 8J of the rack connector of the ADIRU1:

a If the resistance value is out of the specified limit:

repair the above aircraft wiring ASM 341102
install the ADIRU1 AMM 34-12-34-400-001
remove the shunt between pins A/E and J of the electrical connector of the TAT sensor 1
connect the electrical connector of the TAT sensor 1.

b If the resistance value is in the specified limit:

shunt pins A/H and K of the electrical connector of the TAT sensor 1
remove the ADIRU3
do a check of the resistance (R=1.04 ohm plus or minus 0.25 ohm) between pins AA/8H and 8J of the rack connector of the ADIRU3:
. If the resistance value is out of the specified limit:
repair the above aircraft wiring ASM 341102
install the ADIRU1
install the ADIRU3
remove the shunts between pins A/E and J and pins A/H and K of the electrical connector of the TAT sensor 1
connect the electrical connector of the TAT sensor 1.
. If the resistance value is in the specified limit:
disconnect the electrical connector of the TAT sensor 2
do a check of the resistance between pins A/E and J of the TAT sensor 2
* If the resistance value between between pins A/E and J is not correct (Ref. NOTE Para.A(2)(b)1_):
replace the SENSOR-TAT, 2 [11FP2] AMM 34-11-18-000-001 and AMM 34-11-18-400-001.
* If the resistance value between pins A/E and J is correct (Ref. NOTE Para.A(2)(b)1_):
Shunt pins A/E and J of the electrical connector of the TAT sensor 2
remove the ADIRU2 AMM 34-12-34-000-001
do a check of the resistance (R=1.04 ohm plus or minus 0.25 ohm) between pins AA/8H and 8J of the rack connector of the ADIRU2:
** If the resistance value is out of the specified limit:
repair the above aircraft wiring ASM 341102
install the three ADIRUs
remove the shunts between pins A/E and J and pins A/H and K of the electrical connector of the TAT sensor 1
connect the electrical connector of the TAT sensor 1
remove the shunt between pins A/E and J of the electrical connector of the TAT sensor 2
connect the electrical connector of the TAT sensor 2.
** If the resistance value is in the specified limit:
install a new ADIRU-1 [1FP1]
install the ADIRU2 and the ADIRU3
remove the shunts between pins A/E and J and pins A/H and K of the electrical connector of the TAT sensor 1
connect the electrical connector of the TAT sensor 1
remove the shunt between pins A/E and J of the electrical connector of the TAT sensor 2
connect the electrical connector of the TAT sensor 2.
*** After the subsequent flight, if the fault continues:
replace the ADIRU-2 [1FP2] .
**** After the subsequent flight, if the fault continues:
replace the ADIRU-3 [1FP3] .

Subtask 34-13-81-810-071-C ** ON A/C NOT FOR ALL