Vibration with Noise at approximately 51% N1 on Engine 1

TASK 77-00-00-810-916-A
Vibration with Noise at approximately 51% N1 on Engine 1

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 77-32-34-750-001	Fan Trim Balance with the EVMU (one Shot Method)
AMM 77-32-34-860-042	Acquire Unbalance Data During the Flight and Read Unbalance Data

3. Fault Confirmation
Subtask 77-00-00-869-050-C ** ON A/C NOT FOR ALL

A. Prior to perform the fault isolation, the flight vibration data must be available for the engine speeds listed below:

N1 SPEED A319 A320	N1 SPEED A321	N1 tolerance	Time
51% 64% 84% 88% 92%	51% 64% 88% 92% 96%	2% 2% 2% 2% 2%	15sec. 15sec. 15sec. 15sec. 15sec.

if these data are not available acquire these values and do the fault isolation at the first opportunity AMM 77-32-34-860-042.

4. Fault Isolation
Subtask 77-00-00-810-200-C ** ON A/C NOT FOR ALL

A. Balance the engine with the EVMU using the flight data as follows:

NOTE: For information, hereafter are the CFM56-5B One Shot Coefficients:

	N1 bearing vib sensor	N1 bearing vib sensor	TRF vib sensor	TRF vib sensor
96 92 88 84 64 51-52	205 235 300 225 365 500	160 175 200 170 185 205	305 330 400 370 285 550	185 225 245 230 230 45

(1) Cold trim balance the engine using the one shot method AMM 77-32-34-750-001.

NOTE: In SCREWS TO CHANGE menu, push the line key adjacent to the UPDATE indication to memorize the EVMU calculation.

dispatch the aircraft.

(2) If the vibration continues, cold trim balance the engine using the vectorial method AMM 77-32-34-750-001.

NOTE: In SCREWS TO CHANGE menu, push the line key adjacent to the UPDATE indication to memorize the EVMU calculation.

dispatch the aircraft.

(3) If the vibration continues with engine N1 vib higher than 2 units, go to step (2).
(4) If the vibration continues with engine N1 vib less than 2 units, cold trim balance the engine using the vectorial method with the 51% N1 speed only, using current vib manual input option, according to EVMU flight data print.

NOTE: In SCREWS TO CHANGE menu, push the line key adjacent to the UPDATE indication to memorize the EVMU calculation.

[Rev.8 from Aug 2018] 2026.04.04 04:37:35 UTC