DOC AIRBUS | TSM A320FHigh N1 Vibration Level on Engine 2
1. Possible Causes
· bird-strike
· incorrect location of the LPC fan blade annulus filler
· circumferential position and order as indicated by the as-built records or IAE fan blade redistribution tool IAE
1J12312
2 Job Set-up Information
A. Referenced Information
REFERENCE DESIGNATION
Ref. AMM 30-21-49-200-010 Detailed Visual Inspection of the Inlet Cowl Anti-Ice Supply Ducts and
Associated Hardware in the Core Compartment
Ref. AMM 71-00-00-700-012 Test No.9 : Low Pressure (LP) Compressor (Fan) Trim Balancing -
One Shot Method
Ref. AMM 71-00-00-700-022 Test No.8 : Vibration Survey
Ref. AMM 72-00-00-200-010 Inspection of the Engine after Bird Strike, Foreign Object or Slush Ingestion
Ref. AMM 72-00-00-200-011 TAP Test of LP Compressor Fan Blades
Ref. AMM 72-00-00-200-012 Borescope Inspection of the LP Turbine
Ref. AMM 72-00-00-200-017 Inspection of the LP Compressor
Ref. AMM 72-00-00-210-010 Visually Examine the LP Turbine Stage 7
Ref. AMM 72-31-00-400-010 Installation of the LP Compressor (Fan) Module
Ref. AMM 72-31-11-200-010 Inspection of the Low Pressure (LP) Compressor Fan Blades
Ref. AMM 72-31-11-200-012 Inspection of the LP Compressor Annulus Fillers
Ref. AMM 72-31-11-400-010 Installation of the LP Compressor Fan Blades
Ref. AMM 72-38-11-200-010 Inspection of the Inlet Cone and the Inlet Cone Fairing
Ref. AMM 72-51-41-400-010 Installation of the No.5 Bearing Compartment Cover
Ref. AMM 77-32-00-200-010 General Check of the Engine Vibration Indicating System
Ref. AMM 77-32-34-710-041 Operational Check of EVMU through CFDS
Ref. AMM 79-00-00-200-011 Inspection of the Magnetic Chip Detectors for Debris
Ref. AMM 80-13-49-200-010 General Check of the Starter Duct
3. Fault Confirmation
Subtask 77-30-00-710-092-B
A. Test
Not applicable.
NOTE: For additional information on establishing the level of engine vibration, refer to the AMM Test - 8
Vibration Survey Ref. AMM 71-00-00-700-022 .
4. Fault Isolation
Subtask 77-30-00-810-072-B
A. Trouble shooting:
NOTE: The following fault isolation tasks are numbered sequentially in recommended order however, the
fault isolation tasks may be carried out in any order based on individual Operator experience.
NOTE: The N1 vibration level can momentarily increase during icing conditions due to fan blade and/or
spinner icing. To troubleshoot for icing conditions it is permitted to do step (1) and step (2) of the
below procedure only, if the following two criteria are met: follow by Ref. AMM 71-00-00-700-022 .
- The respective engine has no history of high N1 vibration level and the N1 vibration level is set
return back to normal after the applicable operational procedures for high engine vibration in
icing condition are accomplished done.
If no faults are found after performing steps (1) and (2) and N1 vibration levels during test - 8
vibration survey Ref. AMM 71-00-00-700-022 are within limits, return the engine back to service.
- A LPC fan blade inspection for bird-strike , foreign object or slush ingestion damage Ref.
AMM 72-00-00-200-010 has been accomplished.
(1) If you find no fault:
· do an inspection of the inlet cone and the inlet cone fairing Ref. AMM 72-38-11-200-010 .
(2) If you find no fault:
· do an check for incorrect location of the LPC fan blade annulus filler sealing strips Ref.
AMM 72-31-11-200-012 .
(3) If you find no fault:
· Do a check of the turbine case and common nozzle assembly for metallic material and inspect the
LPT for damage Ref. AMM 72-00-00-210-010 .
(4) If you find no fault:
· Do the inspection of the magnetic chip detectors Ref. AMM 79-00-00-200-011 .
(5) If you find no fault:
· Do a check of the LPC fan blade root and fan disc dovetail dry film lubricant, LPC fan blade
chocking pads, LPC disc dovetail ramps and check for correct positioning of the LPC fan blades in
the disc Ref. AMM 72-31-11-400-010 , Ref. AMM 72-31-11-200-010 .
NOTE: One LPC fan blade out of circumferential position (leaning) by one degree will procedure approximately
12 aircraft units of N1 vibration, the Flight Crew Operating Manual (FCOM) limit is
five aircraft units.
- It is important that the LPC fan blades are correctly seated in the disc and dry film lubricant
is applied to the Low Pressure (LP) fan blade roots and fan disc dovetail to assist this. The
LPC fan blades are fitted with chocking pads and the LPC disc with dovetail rear ramps for
the same reason.
- Loss of dry film lubricant with time is normal and loss generally progresses slowly up to approximately
two aircraft units. After this point, dry film lubricant loss generally increases at a
much faster rate and blades may begin to lock out of position.
- IAE recommends a fan trim balance when N1 vibration reaches two aircraft units to prevent
excessive and accelerating dry film lubricant loss.
- One indication of this problem is output from the EVMU showing similar N1 vibration
amount, but different corrected phase angle from run to run. It is important when examining
Engine Vibration Monitoring Unit (EVMU) derived N1 vibration amplitude and phase angle
data that values corrected for N1 speed are used.
(6) If you find no fault:
· Do the BSI of the LPC Ref. AMM 72-00-00-200-017 and the LPT Ref. AMM 72-00-00-200-012 .
(7) If you find no fault:
· Do a TAP test inspection of the engine fan blades Ref. AMM 72-00-00-200-011 .
(8) If you find no fault:
· do the check to ensure that the blades are installed in the correct circumferential position and
order as indicated by the as-built records or IAE fan blade redistribution tool IAE 1J12312 Ref.
AMM 72-31-00-400-010 .
CAUTION: MAKE SURE THAT THE LPC FAN BLADES ARE INSTALLED IN THE CORRECT CIRCUMFERENTIAL
POSITION AND SEQUENCE AS SPECIFIED BY THE IAE TOOL
1J12312. INCORRECT INSTALLATION OF THE BLADES WILL CAUSE AN OUT-OFBALANCE
CONDITION OF THE FAN MODULE, AND ALSO ENGINE VIBRATION.
(9) If you find no fault:
· do the LPC fan blade redistribution Ref. AMM 72-31-11-400-010 .
(10) If you find no fault:
· Do a check of the EVMU system Ref. AMM 77-32-34-710-041 .
(11) If you find no fault:
· Do a check of the vibration transducer harness Ref. AMM 77-32-00-200-010 .
(12) If you find no fault:
· Do a check of the N1 speed probe and harness.
NOTE: The N1 speed probe is a single pole device, the signal from which is passed directly to the
EVMU rather than the EEC. There is only one N1 speed probe fitted on the speed probe harness,
the other three probes are two pole devices the signals from which are passed to the
EEC, one to lane A and one to lane B with one probe spare.
(13) If you find no fault:
· Do a check of the anti-ice duct links Ref. AMM 30-21-49-200-010 .
(14) If you find no fault:
· Do a check of the starter duct links Ref. AMM 80-13-49-200-010 .
(15) If you find no fault:
· Do a check for No.5 bearing damage or No.5 bearing compartment blind cap seal damage Ref.
AMM 72-51-41-400-010 .
NOTE: Oil leakage from the No.5 bearing compartment can pass through a damaged blind cap seal
and result in oil reaching the fan hub leading to N1 vibration.
(16) If you find no fault:
· Do a check for correct location of the LPC fan disc relative to the LPC stub shaft Ref.
AMM 72-31-00-400-010 .
NOTE: The LPC fan disc can be assembled in three circumferential position 120 degreed apart only
one is correct. It is important that the correlation mark on the LPC fan disc denoted by a *
symbol is aligned with a similar mark on the LPC stub shaft.
(17) If you find no fault:
· Do a check of the LPC fan blade axial moment weight details with the original Vital Statistic Log
(VSL data). Overtime, natural wear of the LPC fan blades will result in a change to the axial,
tangential and radial moment weights Ref. AMM 72-31-11-400-010 .
NOTE: Small amounts of wear can produce significant moment weight changes.
- If there are differences, it is recommended that the latest set of moment weights are used
rather than those contained in the VSL.
- If only VSL moment weights are available, a trim balance may be require.
- If any doubt exists over the moment weight details, it is recommended that the fan blade
moment weights are re-measured at the next engine shop visit.
(18) If you find no fault:
· Do an LPC blade trim balance Ref. AMM 71-00-00-700-012 .
NOTE: For additional information on the installation of replacement LPC fan blades Ref.
AMM 72-31-11-400-010 . [Rev.6 from Feb 2017] 2026.04.04 04:37:52 UTC