HIGH PRESSURE TURBINE CLEARANCE CONTROL
The HPTCC valve has integrated dual butterfly valves, driven by a single actuator which receives the fuel pressure from the HMU servo valve.
Each butterfly valve controls its own dedicated compressor stage air pick-up.
The two airflows are mixed downstream of the valve and sent through a thermally insulated manifold to the HPT shroud support, at the 6 and 12 o’clock positions.
The actuator position is sensed by a dual LVDT and sent to both channels of the ECU.
The fuel pressure command from the HMU, Pc, enters the valve at the Turbine Clearance Control (TCC) supply port.
An intermediate pressure, Pcr, is applied on the opposite side of the valve actuator.
There is a drain port on the valve to direct any fuel leaks towards the draining system.

EFG

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CTC-201-224-01
EFFECTIVITY
75-21-00 Page 5
ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03

CFMI PROPRIETARY INFORMATION
CFM56-5B TRAINING MANUAL
EFG
HIGH PRESSURE TURBINE CLEARANCE CONTROL
From various parameters, such as N2, TC, TAT, the ECU calculates the HPTCC valve position and sends electrical signals to the torque motor, within the HMU, to move the valve.
The valves main modes depend on the valve actuator stroke and four air configurations:
- No air, where both butterflies are closed (failsafe
position).

-Ninth, where only the 9th stage air butterfly is open
in a high flow position (idle, take-off, start bleed).

-Mixed, where both butterflies are open and the
actuator stroke determines the amount of each
airflow (climb).

- Full 4th, where only the 4th stage air butterfly is
opened to the maximum position (cruise).

EFG
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CTC-201-287-00
EFFECTIVITY

75-21-00 Page 7
ALL CFM56-5B ENGINES FOR A319-A320-A321
ENGINE SYSTEMS Jan 03

CFMI PROPRIETARY INFORMATION
EFG  CFM56-5B  TRAINING MANUAL 
HIGH PRESSURE TURBINE CLEARANCE CONTROL 
The ECU calculates the HPTC demand, using: 
- N2 (core aerothermo-dynamics and speed). 
- TC (case temperature). 
- TAT (Total Air Temperature). 
- P0 (ambient pressure). 
- T3 (CDP temperature). 
- T25 (Compressor Inlet Temperature). 
- Engine off time (Time between Master Lever OFF 
and Master Lever ON). 
The ECU determines the thermal state of the HP rotor 
and the air available in the primary flow, using N2, TAT. 
It sets a theoretical demand and clearance adjustment for 
thermal expansion according to P0, N2, T3. 
　
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