N2 Overlimit on Engine 1 or 2

TASK 77-00-00-810-851-A
N2 Overlimit on Engine 1 or 2

1. Possible Causes

HMU-1 [4000KC1]
HMU-2 [4000KC2]
ECU [4000KS]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 71-00-00-710-006	Minimum Idle Check
AMM 72-00-00-200-003	Procedure After the Engine has Exceeded the Operational Limits
AMM 72-00-00-200-008	Inspection/Check After the Engine has Exceeded the Operational Limits
AMM 73-21-10-000-001	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-000-002	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-001	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-002	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-60-000-001	Removal of the Electronic Control Unit (ECU)
AMM 73-21-60-400-001	Installation of the Electronic Control Unit (ECU)
AMM 73-21-60-740-007	Correct Time Limited Faults (Non Asterisked) of the Engine Scheduled Maintenance Report
AMM 73-21-60-740-027	Read the Specific Data Report
AMM 77-00-00-710-044	Read of the N1,N2 and EGT Max Pointers

3. Fault Confirmation
Subtask 77-00-00-710-127-A ** ON A/C NOT FOR ALL

A. Test
(1) On the MCDU, read (if available) the DMC Max Value Report AMM 77-00-00-710-044 to note the max N2 value that was recorded during the event as well as the duration of the exceedence (if available from crew report).
If not, read or get the data from the DFDR or QAR.

if no overspeed has been recorded, no further action is necessary.

Subtask 77-00-00-710-127-B ** ON A/C NOT FOR ALL

A. Test
(1) On the MCDU, read (if available) the Specific Data Report AMM 73-21-60-740-027 to note the max N2 value that was recorded during the event as well as the duration of the exceedence (if available from crew report).
If not, read or get the data from the DFDR or QAR.

if no overspeed has been recorded, no further action is necessary.

4. Fault Isolation
Subtask 77-00-00-810-105-A ** ON A/C NOT FOR ALL

A. Do this procedure:

NOTE: The ECAM warning is triggered if the indicated N2 is greater than 105 percent.

(1) If the N2 overlimit is confirmed through the data contained in the DMC report(s) or AIDS data, or DFDR data and if the Crew reported the N2 indication flashing amber on the upper ECAM display unit:

Do the procedure after the engine has exceeded the engine operational limits AMM 72-00-00-200-003.

(a) If the engine is still operable, continue the troubleshooting.
1 Read the Post Flight Report (PFR) or the Scheduled Maintenance Report (SMR) or Class 3 Report or the FADEC Last Leg Report and check for the FMV, HMU, N2 SNSR, VSV, PS3 failure messages AMM 73-21-60-740-007.
a If one or more message is present:

do the troubleshooting related to the failure message(s).

b If nothing is found:

replace the HMU-1 [4000KC1] ( HMU-2 [4000KC2] ) AMM 73-21-10-000-001 and AMM 73-21-10-400-001.
replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

Subtask 77-00-00-810-105-C ** ON A/C NOT FOR ALL

A. Do this procedure:

NOTE: The ECAM warning is triggered if the indicated N2 is greater than 104 percent.

(1) If the N2 overlimit is confirmed through the data contained in the Specific Data Report(s) AMM 73-21-60-740-027 or AIDS data, or DFDR data and if the Crew reported the N2 indication flashing amber on the upper ECAM display unit:

Do the procedure after the engine has exceeded the engine operational limits AMM 72-00-00-200-008.

do the troubleshooting related to the failure message(s).

b If nothing is found:

replace the HMU-1 [4000KC1] ( HMU-2 [4000KC2] ) AMM 73-21-10-000-002 and AMM 73-21-10-400-002.
replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

Subtask 77-00-00-710-265-A ** ON A/C NOT FOR ALL

B. Do a minimum idle check AMM 71-00-00-710-006.
(1) No additional maintenance action is required if the fault is not confirmed.
(2) Repeat the fault isolation procedure if the fault continues.

[Rev.8 from Aug 2018] 2026.04.04 04:37:32 UTC