Inspection of the Engine after N1/N2 Over Speed Operation [PW11]

TASK 72-00-00-210-810-A
Inspection of the Engine after N1/N2 Over Speed Operation

WARNING: BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS INSTRUCTION, INJURY CAN OCCUR.

WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.

ZONE: 400

1. Reason for the Job
Use this procedure to do a visual examination of the engine after N1/N2 over speed operation.
An engine over speed occurs when the N1 or N2 rotors go more than the permitted speed limits. The speed limits are called the N1 redline and the N2 redline. The redline speed limits are shown in Engine Operation Limits and Guidelines, refer to (71-00-00-910-803).
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	COVER - PROTECTION
No specific	1	WRENCH - FLAT

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
400	POWER PLANT, NACELLES AND PYLONS

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 31-32-00-860-012-A	Procedure to Get Access to the SYSTEM REPORT/TEST/ENG Page
TASK 71-00-00-720-811-A	Test No. 3A - Idle Power Test
TASK 71-00-00-860-833-A	Procedure to Prevent Engine Motoring
TASK 72-00-00-000-805-A	Removal of the High (N2) Rotor-Turning Equipment
TASK 72-00-00-210-812-A	General Visual Inspection (GVI) of the Engine Exhaust Area
TASK 72-00-00-210-816-A	Visual Examination of the Engine
TASK 72-00-00-400-805-A	Installation of the High (N2) Rotor Turning Equipment
TASK 72-31-00-290-802-A	Borescope Inspection of the Low Pressure Compressor (LPC) Assembly
TASK 72-35-00-290-801-A	Borescope Inspection of the High Pressure Compressor (HPC) Assembly
TASK 72-51-00-290-802-A	Borescope Inspection of the 1st and 2nd Stage Turbine Blades
TASK 72-53-00-200-801-A	Borescope Inspection of the Low Pressure Turbine (LPT) Assembly
TASK 73-21-00-710-806-A	Test No.7 - EEC Operation Test (Self Test)
Inspection of the Engine after N1 Over Speed Operation
Inspection of the Engine after N2 Over Speed Operation

3. Job Set-up
Subtask 72-00-00-861-056-A ** ON A/C NOT FOR ALL

A. Energize the aircraft electrical circuits (Ref. AMM TASK 24-41-00-861-002).

Subtask 72-00-00-941-208-A ** ON A/C NOT FOR ALL

B. Safety Precautions
(1) Do the procedure to prevent engine motoring
(Ref. AMM TASK 71-00-00-860-833)

Subtask 72-00-00-860-110-A ** ON A/C NOT FOR ALL

C. Aircraft Maintenance Configuration
(1) On the left or right MCDU, get to the SYSTEM REPORT/TEST ENG page (Ref. AMM TASK 31-32-00-860-012).
(2) Get the record of the over speed operation from the Multipurpose Control and Display Unit (MCDU) screen as follows:
(a) Get the fault or discrepancy reports for the last flight.
(b) Get the record of the over speed operation from the engine exceedance report.
(c) Depending on which rotor exceeded the limit, print the record on N1 or N2 PEAK value and N1 or N2 TIME the engine rotor exceeded the redline limit.

4. Procedure

CAUTION: WIPE CLEAN ALL PARTS AND TOOLS AS NECESSARY TO REMOVE UNWANTED DEBRIS AND PREVENT DAMAGE TO THE ENGINE.

Subtask 72-00-00-210-172-A ** ON A/C NOT FOR ALL

A. Inspection of the Engine after N1 Over Speed Operation

Inspection of the Engine after N1 Over Speed Operation ** ON A/C NOT FOR ALL

(1) Removal of the protection covers:

CAUTION: REMOVE THE PROTECTION COVERS FROM THE OPENINGS AS NECESSARY TO PREVENT ENGINE DAMAGE.

(a) Make sure that you remove all the necessary COVER - PROTECTION to prevent damage to the engine.
(2) Do the following inspections for N1 rotor over speed exceedance. Get the record of N1 over speed operation and do the necessary inspections for areas A, B or C.
(a) N1 over speed area A - No inspection is necessary if the N1 over speed condition was for a time of five seconds or less (transient condition).
(b) N1 over speed area B - If the N1 over speed condition was for a time of more than five seconds, do the steps that follow:
1 Examine the engine air intake for unwanted material and damage (Ref. AMM TASK 72-00-00-210-816).
2 Examine the turbine exhaust for pieces of metal and damage (Ref. AMM TASK 72-00-00-210-812).
(c) Do a check to see if the N1 rotor turns as follows:

NOTE: Turn the fan clockwise as seen from the rear (normal operation). If the fan is accidentally turned counterclockwise, there can be some resistance. This condition is permitted, but do not continue to turn the fan in the counterclockwise (incorrect) direction.

1 Turn the Low Pressure Compressor (LPC) fan rotor carefully with your hands.
2 The N1 rotor must turn freely for 360 deg (360 deg).
(d) Do a check to see if the N2 rotor turns correctly:

CAUTION: BEFORE YOU REMOVE THE N2 CRANK-PAD COVER, PUT A CONTAINER IN POSITION BELOW IT TO COLLECT THE UNWANTED OIL. THE MAIN GEARBOX OIL-LEVEL CAN BE HIGHER THAN THE N2 CRANK-PAD COVER IF THE ENGINE DID NOT OPERATE DURING EIGHT HOURS. IF YOU DO NOT OBEY THIS INSTRUCTION, OIL CAN SPILL AND CAUSE DAMAGE TO THE ENGINE PARTS.

1 Remove the gearbox crank pad cover (for the N2 rotor turning) (Ref. AMM TASK 72-00-00-000-805).
2 Turn the N2 rotor with a WRENCH - FLAT installed on the gearbox crank pad to turn the N2 rotor.
3 The N2 rotor must turn freely for 360 deg (360 deg).
4 Install the gearbox crank pad cover (Ref. AMM TASK 72-00-00-400-805).
(e) Do a check of the N1 speed indication system for satisfactory operation.

NOTE: Refer to the Trouble Shooting Manual (TSM), Fault Isolation section for N1 speed indication system faults.

(f) If you do not find any damage or problems when you do the above inspection steps, the engine can continue in service after you do the steps that follow:
1 Find and correct the cause of the N1 over speed condition.
2 Do these tests for the satisfactory operation of the engine:

The idle power test (cowls open) (Ref. AMM TASK 71-00-00-720-811) and
The EEC FADEC System Operation Test (self test) (Ref. AMM TASK 73-21-00-710-806).

(g) If you see any damage when you do the above inspection steps, you must do a borescope inspection of the engine as follows:
1 Do a borescope inspection of the LPC. Examine the blades and vanes very carefully for damage (Ref. AMM TASK 72-31-00-290-802).
2 Do a borescope inspection of the High Pressure Compressor (HPC) airfoils (Ref. AMM TASK 72-35-00-290-801).
3 Do a borescope inspection of the Low Pressure Turbine (LPT) vanes and blades (Ref. AMM TASK 72-53-00-200-801).
(h) If you do find damage after the borescope inspection follow the recommended disposition:
1 N1 over speed area C - Remove the engine from service and send the engine to the shop to do the steps that follow:

NOTE: Before you remove the engine from service, do a check of the N1 speed indication system for satisfactory operation. Refer to the TSM, Fault Isolation section for N1 speed system faults.

a Disassemble the N1 engine parts that turn (the fan rotor, LPC and LPT).
b Do an inspection of all the N1 engine parts that turn.

Subtask 72-00-00-210-173-A ** ON A/C NOT FOR ALL

B. Inspection of the Engine after N2 Over Speed Operation

Inspection of the Engine after N2 Over Speed Operation ** ON A/C NOT FOR ALL

(1) Do the following inspections for N2 rotor over speed exceedance. Get the record of N2 over speed operation and do the necessary inspections for areas A, B or C:
(a) N2 over speed area A - No inspection is necessary if the N2 over speed condition was for a time of five seconds or less (transient condition).
(b) N2 over speed area B - If the N2 over speed condition was for a time of more than five seconds, do the steps that follow:
1 Examine the engine air inlet for unwanted material and damage (Ref. AMM TASK 72-00-00-210-816).
2 Examine the turbine exhaust for pieces of metal and damage (Ref. AMM TASK 72-00-00-210-812).
(c) Do a check to see if the N1 rotor turns as follows:

1 Turn the LPC fan rotor carefully with your hands.
2 The N1 rotor must turn freely for 360 deg (360 deg).
(d) Do a check to see if the N2 rotor turns correctly:
1 Remove the gearbox-crank pad cover (for the N2 rotor turning) (Ref. AMM TASK 72-00-00-000-805).
2 Turn the N2 rotor with a WRENCH - FLAT installed on the gearbox-crank pad to turn the N2 rotor.
3 The N2 rotor must turn freely for 360 deg (360 deg).
4 Install the gearbox-crank pad cover (Ref. AMM TASK 72-00-00-400-805).
(e) Do a check of the N2 speed indication system for satisfactory operation.

NOTE: Refer to the TSM, Fault Isolation section for N2 Speed System Faults.

(f) If you do not find any damage or problems when you do the above inspection steps, the engine can continue in service after you do the steps that follow:
1 Find and correct the cause of the N2 over speed condition.
2 Do these tests for the satisfactory operation of the engine:

The idle power test (cowls open) (Ref. AMM TASK 71-00-00-720-811)
The EEC FADEC system-operation-test (self test) (Ref. AMM TASK 73-21-00-710-806).

(g) If you find any damage when you do the above inspection steps, you must do a borescope inspection of the engine as follows:
1 Do a borescope inspection of the HPC stage 6-8 airfoils (Ref. AMM TASK 72-35-00-290-801).
2 Do a borescope inspection of the High Pressure Turbine (HPT). Examine the 1st stage turbine blades carefully (Ref. AMM TASK 72-51-00-290-802).
(h) If you do not find damage after the borescope inspection, follow the recommended disposition:
1 N2 over speed area C - Remove the engine from service and send the engine to the shop to do the steps that follow:

NOTE: Before you remove the engine from service, do a check of the N2 speed indication system for satisfactory operation. Refer to the TSM, Fault Isolation section for N2 speed systems faults.

a Disassemble the N2 engine parts that turn (HPC and HPT).
b Do an inspection of all the N2 engine parts that turn.
(2) Examine the assembly for foreign objects, damage and correct assembly.
(3) Installation of protection covers:

CAUTION: INSTALL PROTECTION COVERS ON ALL THE OPENINGS IMMEDIATELY TO PREVENT DAMAGE TO THE ENGINE.

(a) Make sure that you install COVER - PROTECTION as necessary to prevent damage to the engine.

[Rev.10 from 2021] 2026.04.01 12:57:06 UTC