Message Name:

ENGINE CONTROL REVERTS TO N1 CTR ON APU SHUTDOWN

Engine Control Mode indication changed from EPR to N1 Control after APU shutdown.

• P20/T20 Probe
• EEC
• Solid State Power Contactor 4 (SSPC) (K10)
• Air Data Computer (ADC) 1 (A27)
• Junction Box 3 (JB3)
• Secondary Power Distribution Assembly (SPDA) 1 (A13)
• APU Start Contactor Assembly (ASCA) (A48)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

NOTE: Only the ADC 1 is powered on battery power and as per the EEC N1 Control logic, if the EECs lose the ADC source input data, the EEC reverts to N1 Control.
NOTE: If the ADC 1 DEGRADED Cyan CAS message is posted after APU shutdown (battery power) even for a brief moment, this is an indication the EECs lost the ADC data.
NOTE: On battery power, both Avionic and APU batteries provide power to the battery bus.
NOTE: Reference IPC 24-61-21 for SSPC4 (K10).
NOTE: SSPC5 (K3) for the APU battery is located in the APU Start Contactor Assembly (ASCA).

1. Is the issue present on both engines or only one engine?

   1. If present on one engine, continue next step.
   2. If present on both engines, continue step 7.

2. Interchange P20/T20 Probe between engines. Does the engine control issue follow the P20/T20 Probe?

   1. If YES, replace P20/T20 Probe.
   2. If NO, continue next step

3. Interchange EECs. Does the engine control issue follow the EEC?

   1. If YES, replace EEC.
   2. If NO, continue next step.

4. Perform wiring checks between P20/T20, EEC and ADC1. Are wiring checks satisfactory?
   

   ADC1 (Bus1) TO L EEC

   FROM	TO	RESULTS
   A27P1-60	P1045-34 Ch A
   A27P1-60	P1048-59 Ch B
   A27P1-61	P1045-56 Ch A
   A27P1-61	P1048-35 Ch B

   ADC1 (Bus 2) TO R EEC

   FROM	TO	RESULTS
   A27P1-63	P1048-34 Ch B
   A27P1-64	P1048-56 Ch B

   ADC 1 TO L ENG P20/T20

   FROM	TO	RESULTS
   A27P1-31	P701-2
   A27P1-32	P701-3

   ADC 2 TO R ENG P20/T20

   FROM	TO	RESULTS
   A28P1-31	P701-2
   A28P1-32	P701-3

   ENG EEC TO P20/T20

   FROM	TO	RESULTS
   P1044-46	P700-5
   P1044-25	P700-6
   P1044-45	P700-7
   P1044-44	P700-4

   1. If YES, continue step 7.
   2. If NO, repair wiring.
   3. if wiring check is not good between ADC 1 & LH EEC, proceed to next step.

5. Perform wiring check between ADC 1 & JB3 (PCB5). Are wiring checks satisfactory?
   

   ADC1 TO JB3

   FROM	TO	RESULTS
   A27P1-60	JB3CP1-7F
   A27P1-61	JB3CP1-7G

   1. If YES, continue next step.
   2. If NO, repair wiring.

6. Perform wiring check between JB3 (PCB5) & LH EEC. Are wiring checks satisfactory?
   

   JB3 (PCB5) TO L EEC

   FROM	TO	RESULTS
   JB3CP1-7H	P1045-34 (CH A)
   JB3CP1-7J	P1045-56 (CH A)
   JB3CP1-7K	P1048-59 (CH B)
   JB3CP1-8A	P1048-35 (CH B)

   1. If YES, replace JB3 PCB5.
   2. If NO, repair wiring.

7. Is ADC 1 DEGRADED Cyan CAS message posted for a brief moment after APU shutdown, then clears?

   1. If YES, continue next step.
   2. If NO, continue step 9.

8. Interchange ADC 1 with ADC 3, located on same side of flight deck. Does the engine control issue follow the ADC?

   1. If YES, replace ADC.
   2. If NO, continue next step.
      

9. Interchange SPDA 1 with another SPDA. Does the engine control issue follow the SPDA 1?

   1. If YES, replace SPDA.
   2. If NO, continue with next step.

10. Interchange SSPC 4 (K10) inside DCPC with K9, K7 or K8. Does the engine control issue follow the SSPC 4 (K10)?

    1. If YES, replace SSPC 4 (K10).
    2. If NO, continue next step.
       

11. Replace APU Start Contactor Assembly (ASCA) A48, which contains the K3 relay.