Maintenance Practices 201 ALL Actuation Procedure - External 201 Pressure Source Actuation Procedure - Manual 204 Movement ACTUATOR - BLEED VALVE AND 75-32-04
BALLSCREW Removal/Installation 401 ALL Inspection/Check 601 ALL
ACTUATOR - BLEED VALVE AND 75-32-03
MASTER BALLSCREW Removal/Installation 401 ALL Inspection/Check 601 ALL
MECHANISM - BLEED VALVE STOP 75-32-02 Removal/Installation 401 ALL
75-CONTENTS
CBEJ Page 3 Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
CHAPTER 75 - AIR
TABLE OF CONTENTS
_________________
Chapter Section
Subject_______ Subject ____ Effectivity_______ Page ___________
Adjustment/Test 501 [*] [*] ENGINES POST-CFMI-SB 72-580
Inspection/Check 601 ALL
MOTOR - BLEED VALVE FUEL GEAR 75-32-01 Removal/Installation 401 ALL Inspection/Check 601 ALL
SHAFT - FLEXIBLE 75-32-07 Removal/Installation 401 ALL VARIABLE BLEED VALVE (VBV) 75-32-05
FEEDBACK CABLE Removal/Installation 401 ALL Adjustment/Test 501 ALL Inspection/Check 601 ALL
BLEED BIAS SENSOR SYSTEM 75-33-00
Description and Operation 1 ALL General 1 Sensor - Bleed Bias 1 Operation 1
Inspection/Check 601 ALL
SENSOR - BLEED BIAS 75-33-01
Removal/Installation 401 ALL
5TH-STAGE START BLEED SYSTEM 75-34-00
Description and Operation 1 ALL General 1 Valve - 5th-Stage Start Bleed 1 Operation 5
Adjustment/Test 501 ALL Inspection/Check 601 ALL VALVE - 5TH-STAGE START BLEED 75-34-01
Removal/Installation 401 ALL
75-CONTENTS
CBEJ Page 4 Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
AIR - DESCRIPTION AND OPERATION
_______________________________
1. General (Fig. 1)
_______
A. The engine air systems are comprised of:
(1)
Forward and Aft Bearing Sump Pressurizing
(2)
Accessory Cooling, AMM 75-20-00
(a)
Engine External Accessories Cooling, AMM 75-21-00
(b)
High Pressure Turbine Clearance Control System, AMM 75-24-00
(3)
Compressor Control
(a)
Variable Stator Vane Actuation System, AMM 75-31-00
(b)
Variable Bleed Valve System, AMM 75-32-00
(c)
Bleed Bias Sensor System, AMM 75-33-00
(d)
5th-Stage Start Bleed System (On Some Engines), AMM 75-34-00
B. A preferred direction of air circulation is established by means of pressurizing the forward and aft bearing sump labyrinth seals. This pressure exceeds the internal pressure of the sump. The sumps are vented by the center vent tube, located inside the low pressure turbine shaft, to prevent overpressures in the sump.
C. Accessory cooling includes the following:
(1)
Engine internal cooling, which uses bleed air from different parts of the engine to cool the high pressure compressor (HPC) disk and spool, the high pressure turbine (HPT) disk, blades and nozzle vanes, and the low pressure turbine (LPT) disk and nozzle vanes.
(2)
Turbine case cooling, which uses fan discharge air to cool the LPT case.
(3)
Engine external accessories cooling, which includes generator cooling (provided by fan discharge air) and ignition leads cooling (provided by booster discharge air).
(4)
A HPT clearance control system, which uses cooling air from the HPC section to optimize HPT blade clearance, allowing maximum HPT performance.
D. Compressor control provides engine operational flexibility throughout the engine operating range by controlling airflow to and through the HPC and by monitoring bleed demands. Compressor control includes the variable stator vane (VSV) actuation system, the variable bleed valve (VBV) system, the bleed bias sensor system and, on some engines, the 5th-stage start bleed system. The VBV system controls airflow quantity to the HPC and the VSV system controls airflow through the HPC. The bleed bias sensor system monitors 9th-stage HPC bleed rates to provide automatic resetting of the acceleration schedule, allowing rapid acceleration rates and adequate stall margins as a function of bleed demands. The 5th-stage start bleed system reduces pressure in the HPC during start to increase engine stall margin.
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