(6)
Trim balance is only used to correct stable low rotor related (1EL) vibration.
(7)
The total vector sum of the trim balance weights and the weights installed for component (LPC) balance must not be more than the limits that follow:
. Fan Plane: 50 oz-inches (36,000 g.mm)
. LPT: 48 oz-inches (34,560 g.mm)
NOTE: If more correction weight than permitted is necessary, you
____ must examine the engine for incorrect assembly and part damage.
(8) Identify all the trim balance weights permanently with the letters "TB".
NOTE: The balance weights installed on the fan hub during LPC
____ balance are not identified with the letters "TB".
(9)
This procedure includes instructions for these subtasks:
(a)
Installation of engine equipment and external cables.
(b)
Listing of available fan and turbine plane counterweights.
(c)
Instruction of the installation of the counterweights.
(d)
Engine test requirements.
(e)
Supplemental PBS-4100 operation and setup information.
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(10) Definitions:
(a) (b) Once Per Revolution N1 Speed Reference: Once every revolution a signal is received by the N1 speed transducer. The short tooth of the tachometer gear on the turbine shaft coupling makes the signal.N1 Reference Mark: Ink mark on a fan blade or the hub which identifies the short tooth location.
(c) (d) 1EL: The vibration of the low pressure rotor.Vibration Units: Vibration should be in mils (mm) and vibration velocity in inches per second (mm per second).
1 mil = 0.001 inch (0.025 mm)
(e) Phase Angle Lag: If the low pressure rotor is not balanced, the vibration analyzer will give its angular location. The phase angle lag is the angle between the actual location of the unbalance and the location the analyzer shows.
NOTE:____ This procedure uses phase measurement equipment that measures from the N1 speed pulse to the vibration pulse (maximum). Measure positive angles, in this coordinate system, in the opposite direction from the direction in which the engine turns. Some phase measurement equipment, such as the MTI equipment, measure positive angles in the direction in which the engine turns (lead angle).
(f) (g) Phase Angle: The angle between the signal from the vibration transducer and the signal from the N1 speed reference. The speed reference is given once per revolution.Sensitivity: The moment weight that causes 1.0 mil (0.025 mm) of vibration.
(h) (i) Once Per Revolution N1 Speed Reference: Once every revolution a signal is received by the N1 speed transducer. The short tooth of the tachometer gear on the turbine shaft coupling makes the signal. As an alternative procedure, use an optical tachometer for the once per revolution N1 speed reference.N1 Reference Blade: Fan blade with an ink mark to identify the short tooth location.
(j) (k) (l) Stable Vibration: A Stable Vibration is a vibration of which the vibration maximum does not change by more than one-fourth of the average vibration during 30 seconds of the engine operation.Vibration Survey: To do a test and write the engine vibration data against the rotational speed during an engine acceleration or deceleration. This finds which engine speeds give the maximum vibration levels which are not permitted.Trim Balance Survey: To do a test and write the vibration amplitude and phase angle data of the low rotor. The vibration amplitude is measured while the engine is stable at the peak vibration level. You can then calculate the correct weight.
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
B. Equipment
(1)
MTI 2825-4045 Bracket - "A" Flange Vibration Pick-up,
Mechanical Technology Inc.,
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：747-400 AMM 飛機維護手冊 發動機 ENGINE 1(113)
