(2)
An inner shroud, whose inner face is lined with abradable material facing both the forward rotating air seal, the booster spacers sealing lips and the aft blade retainer.
(3)
Stator vanes are welded to the outer shroud and retained on the inner shroud by the abradable material. First stage vane assembly has 100 vanes; 2nd-thru 4th-stage vane assemblies each have 112 vanes.
B. The outer shroud rear flange of the 4th-stage vane assembly is bolted to the front face of the fan frame. The inner shroud rear flange is rabbetted to form an interference fit with a corresponding flange on the fan frame.
C. The outer shroud of the 3rd-stage vane assembly has an orifice at the
3:30 o'clock position providing for primary airstream borescope inspection.
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72-31-00
ALL ú ú C01 Page 3 ú Jul 15/96
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
FAN AND BOOSTER - ADJUSTMENT/TEST
_________________________________
1. General
_______
A. This procedure gives the instructions to trim balance the No. 1 bearing (FAN) and the low pressure turbine (LPT).
(1)
The trim balance procedure is done in the conditions that follow.
(a)
It is done to decrease the FAN or LPT vibration levels that are equal to or more than 8.0 mils DA (double amplitude).
(b)
It is done when the correction, after the replacement or repair of a fan blade, is more than 158 gram-inches (400 g-cm).
(2)
The trim balance procedures cause the vibration levels (FAN and LPT) to be not more than 2 units AVM during the ground operations for all engine operation speeds. 2 units AVM is the same as 3.5 mils double amplitude (DA) FAN and 4.0 mils DA TRF which is measured at the turbine rear frame.
B. The 3 procedures available to trim balance the N1 rotor are the analyzer procedure, the three-shot plot procedure, and the inflight data trim balance procedure.
(1)
The inflight data trim balance procedure uses data stored in the AVM to balance the engine. The AVM records and calculates trim balance data using signals from the No. 1 bearing and turbine rear frame (TRF) vibration sensors. Trim balance data is available from the AVM for the last 6 flights. The data is accessed using the front panel display on the the AVM. The following trim balance data is available from the AVM:
(a)
The current imbalance data.
(b)
The current configuration of the balance weights and their installed locations on the FAN.
(c)
The 1-plane balance solution (FAN only).
(d)
The 2-plane balance solution (FAN and LPT).
(e)
The AVM can be updated with any FAN weights that are installed.
(2)
The analyzer procedure uses a trim balance analyzer which gives an unbalance indication (filtered for a frequency of one for each turn of the N1 rotor) and a phase angle of the imbalance location. An imbalance is when something is not balanced. These indications are shown as a quantity and location on the rotor.
(a)
When the engine operation data is put into a computer, a correction weight and position is then calculated.
(b)
If the correction does not cause a satisfactory result, the procedure is done again with a second weight and position. This gives a more accurate result.
(c)
An analyzer with built-in software can calculate equivalent results.
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