(2) Close the thrust reverser doors: (Ref. TASK 78-36-00-410-040). FOR 1000EM1 451AL, 452AR FOR 1000EM2 461AL, 462AR
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B. Make the thrust reverser serviceable (Ref. TASK 78-30-00-081-041).
(1) Remove the warning notice(s). Subtask 75-21-10-410-055
C. Close Access
(1) Close the fan cowls (Ref. TASK 71-13-00-410-040):
FOR 1000EM1
437AL, 438AR
FOR 1000EM2
447AL, 448AR.
(2) Remove the access platform(s).
(3) Remove the warning notice(s).
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E E Aug 01/05 E E ECES E LPT ACTIVE CLEARANCE CONTROL SYSTEM - DESCRIPTION AND OPERATION
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1. General
_______ (Ref. Fig. 001) The low pressure turbine casing is cooled by fan discharge air sprayed through an array of piping and small air jets that impinge on the outside surface of the casing. The LPT active clearance control system controlled by a valve through FADEC system maintains LPT case shroud clearances relative to LPT rotor blade tips.
2. Description
___________ (Ref. Fig. 002) The clearance control system supply fan bleed air from the inner barrel scoop of the thrust reverser to the LPT casing via circular pipings fitted around the shroud support structure. The fan bleed air flow is modulated by ECU according to engine operating conditions.
3. LPT Clearance Control Valve
___________________________
(Ref. Fig. 003)
A. Description LPT clearance control valve is a butterfly valve, the valve consists of an outer housing, a control plate, a linear actuator, 2 RVDT sensors for feedback signals and a butterfly valve actuation. Under control of the PCR pressure applied at its head end and a PC/PB modulated pressure applied at its rod end, the linear actuator moves a rack controlling both the opening and closing of the butterfly valve which regulates the amount of air required for cooling the turbine as a function of the engine operating configuration (engine rating).
B. Operation (Ref. Fig. 002) The ECU modulates the pressure of one of the piston chambers through the HMU. The HMU supplies a reference pressure to the second chamber. The ECU controls the travel of the piston and valve butterfly according to the engine parameters. The butterfly of the valve opens when the engine rating increases and closes when it decreases. When the engine is shut down, the valve butterfly is fully open.
4. LPT Cooling Flow Function
_________________________ (Ref. Fig. 004, 005) LPT cooling air flow, controlled by LPTACC valve depends on the operating conditions and engine characteristics. Flow functions defined are validated for ventilation calculation purpose.
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LPTACC - Schematic
Figure 001
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LPTACC Valve Operation
Figure 002
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LPT Active Clearance Control Valve
Figure 003
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LPT Cooling Flow Function
Figure 004
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LPT Cooling Flow Function
Figure 005
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LPT ACTIVE CLEARANCE CONTROL VALVE - REMOVAL/INSTALLATION
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TASK 75-22-10-000-002
Removal of the Low Pressure Turbine Active Clearance Control (LPTACC) Valve
1. Reason for the Job
__________________
Self Explanatory
2. Job Set-up Information
______________________
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