Failure of the Yaw Damper System

TASK 27-26-00-810-801-A
Failure of the Yaw Damper System

1. Possible Causes

FAC-1 [1CC1]
FAC-2 [1CC2]
SERVO ACTR-YAW DAMPER, 1 [3CC1]
SERVO ACTR-YAW DAMPER, 2 [3CC2]
wiring

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ESPM 2055500
AMM 22-66-34-000-002	Removal of the FAC
AMM 22-66-34-400-002	Installation of the FAC
ASM 226804
AMM 27-24-00-710-002	Operational Test of the Rudder Servocontrols with Individual Hydraulic System
AMM 27-26-51-000-001	Removal of the Yaw Damper Servo Actuator
AMM 27-26-51-400-001	Installation of the Yaw Damper Servo Actuator

3. Fault Confirmation

CAUTION: DO NOT SWAP FLIGHT AUGMENTATION COMPUTERS. IF THERE IS A SHORT CIRCUIT, YOU WILL CAUSE DAMAGE TO A SERVICEABLE COMPUTER WHEN YOU SWAP THEM.

Subtask 27-26-00-710-050-A ** ON A/C NOT FOR ALL

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

4. Fault Isolation

NOTE: This Fault Isolation is for the system 1, for the system 2, use the indications between the parentheses.

Subtask 27-26-00-810-050-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the crew observation F/CTL - Yaw and roll jerk very hard:
(1) Remove the FAC related to the system which was active at the time of the event AMM 22-66-34-000-002.

NOTE: In normal configuration, the FAC-1 [1CC1] servoes the Green yaw damper servo actuator (3CC1), the FAC-2 [1CC2] servoes the Yellow yaw damper servo actuator (3CC2).

(2) At the FAC receptacle, do a check of the resistance and insulation of the LVDT of SERVO ACTR-YAW DAMPER, 1 [3CC1] ( SERVO ACTR-YAW DAMPER, 2 [3CC2] ) (COM) between pins AB/2E and AB/2F, and between pins AB/3E and AB/3F ASM 226804.

NOTE: The resistance of the two secondary windings must be between 30 Ohms and 500 Ohms.
The insulation must be more than 100 Megohms.

(a) If the check is correct:
1 Replace the FAC-1 [1CC1] ( FAC-2 [1CC2] ) AMM 22-66-34-000-002 and AMM 22-66-34-400-002.
2 If the fault continues:

Do a check of the wiring between the LVDT and the FAC ASM 226804 for correct connections.

3 If the fault continues:

Replace the SERVO ACTR-YAW DAMPER, 1 [3CC1] ( SERVO ACTR-YAW DAMPER, 2 [3CC2] ) AMM 27-26-51-000-001 and AMM 27-26-51-400-001.

4 Do the Operational test of the rudder servocontrols with individual hydraulic system AMM 27-24-00-710-002.
(b) If the check is not correct:
1 Clean the connector A of the SERVO ACTR-YAW DAMPER, 1 [3CC1] ( SERVO ACTR-YAW DAMPER, 2 [3CC2] ) ESPM 2055500.
2 At the FAC receptacle, do again a check of the resistance and insulation of the LVDT.
a If the check is correct, no further maintenance action is necessary.

NOTE: After the subsequent flight, if the fault continues, replace the SERVO ACTR-YAW DAMPER, 1 [3CC1] ( SERVO ACTR-YAW DAMPER, 2 [3CC2] ) AMM 27-26-51-000-001 and AMM 27-26-51-400-001.

b If the check is not correct, go to Para. (3).
(3) At the yaw damper, do a check of the resistance and insulation between pins A/C and A/B, and between pins A/K and A/J ASM 226804.
(a) If the check is not correct, replace the SERVO ACTR-YAW DAMPER, 1 [3CC1] ( SERVO ACTR-YAW DAMPER, 2 [3CC2] ) AMM 27-26-51-000-001 and AMM 27-26-51-400-001
(b) If the check is correct, repair the wiring ASM 226804.

[Rev.8 from Aug 2018] 2026.04.04 04:27:29 UTC