CFM56-7B CO-216 Engine Systems

COURSE OUTLINE CFM56-7B
Engine SystemsFebruary 2005 CO-216 Level 4

Engine Systems

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FOREWORD

Detailed information for the course that you are going to follow, is available from a CD-ROM, containing the full version of the Training Manual.

To help you follow the lessons easily and retain as much information as possible, you have been provided with a summary of the training manual.

The summary is called a Course Outline.

The Course Outline contains black & white copies of the images displayed during the course accompanied by a few lines of easy-to-read text, which provide

complementary information.

To the right of the drawing, there is a space where you can write down notes, if you so wish.

If you have any questions, please ask your instructor, who will be happy to help.

Engine Systems CFM56-7B Blank Page

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Engine Systems

Introduction CFM56-7B

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The FADEC system takes complete control of the engine in response to command inputs from the aircraft. It also provides information to the aircraft for cockpit

indications, engine condition monitoring, maintenance reporting & troubleshooting. The EEC electronically performs engine control calculations and monitors the engine’s condition, using feedback from peripheral components. The HMU converts EEC signals into hydraulic pressures to drive the engine’s valves and actuators.

Engine Systems

Introduction CFM56-7B

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The FADEC system communicates with the aircraft computer through channels A and

B of the EEC. The EE

C receives operational commands from the CDS/DEU’s, which act as a conduit for data exchange between the EEC and aircraft systems.

The EEC has 2 identical channels linked thru a CCDL. Both channels are always operational, but only the channel in control delivers output commands. Control inputs are dual, some indicating inputs are shared, and monitoring parameters are single.

Engine Systems

Introduction CFM56-7B

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The EEC calculates a position, compares it with the actual position and calculates a demand. Through the HMU, the EEC moves the component, receives position feedback and repeats the process until there is no longer a position difference.

Engine Systems

Electronic Engine Control CFM56-7B

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The EEC is secured on the fan case at the 2 o’clock position, through 4 mounting bolts with shock absorbers. Cooling air, picked up from an air scoop, is routed into the EEC internal chamber, and exits through a cooling air outlet.

The EEC has a front panel assy (FPA) and a side interface assy (SIA) for electrical connections, and a pressure sub-system (PSS) with transducers for pressure connections. The rear cover gives access to channel A and B circuit boards.

Engine Systems

Electronic Engine Control CFM56-7B

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The EEC has 11 electrical connectors located on the FPA and the SIA. Each connector has a unique key pattern which only accepts the correct corresponding cable plug.

Plugged into P11 on the SIA, the ID plug supplies configuration data to the EEC. The plug includes a coding circuit equipped with fuse links and push-pull links, which ensure or prohibit connections between the pins.

Engine Systems

Electronic Engine Control CFM56-7B

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Fuse links give thrust information to the EEC at power up. They also provide a bump option and plug type identification.They are made by metallization of an area between two contacts of the coding circuit and cannot be reconfigured.

Push-pull links consist of switch mechanisms located between 2 contacts and can be manually opened or closed. Push-pull links provide the EEC with engine configuration information such as SAC with/without BSV, or DAC.

Engine Systems

Electronic Engine Control CFM56-7B

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The EEC is a digital computer with related input and output, memory, control and power supply circuits. Each EEC channel has 1 Input/Output Module (IOM), 1 Digital Processing Module (DPM) and 1 Power Supply Module (PSM).

Transducers in the PSS convert 4 pneumatic signals into electrical signals. The 2 engine control pressures (P0, PS3) are supplied to both channels. Optional PMUX pressures PS13 & P25 are supplied respectively to channel A & channel B.

Engine Systems

Electronic Engine Control CFM56-7B

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Redundant power sources ensure an uninterrupted and failsafe power supply to the EEC. A logic circuit, within the EEC, automatically selects the correct power source in the event of a failure.

At engine start, the A/C sends electrical power to the EEC, thru an alternate power relay, in turn supplying EEC internal relays. The EEC monitors N2 speed, and supply circuit is different according to N2 conditions: N2<12%, 12%15%.

Engine Systems

Electronic Engine Control CFM56-7B

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The control alternator is lubricated with AGB engine oil. Two separate windings provide a 3-phase power signal to each EEC connector. The alternator continues to meet all electrical requirements at N2 > 45%, even if one phase fails in one or both windings.

Engine Systems

Engine Sensors CFM56-7B

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To control the engine, the EEC uses data from sensors installed at aerodynamic

stations and various engine locations. Sensors at aerodynamic stations have the same number as the station and other sensors have a particular name.

The engine has 2 speed sensors, 2 RTD sensors, 3 thermocouples, 4 pressure sensors (2 optional), and 2 vibration sensors.

Engine Systems

Engine Sensors CFM56-7B

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Both N1 and N2 speed sensors operate on the same principle. They are induction type tachometers providing frequency outputs directly proportional to the rotational speed of the rotor.

The N1 speed sensor is mounted through the 4 o’clock fan frame strut and faces a sensor ring having one tooth thicker than the others. This generates a stronger pulse which is used as a phase reference in vibration analysis.

Engine Systems

Engine Sensors CFM56-7B

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The N2 speed sensor is installed on the front face of the AGB at 9 o’clock and secured with 2 bolts.

The RTD’s sensing element is inserted in the airstream and the airflow heat changes the electrical resistance. The EEC determines the resistance by sending an excitation signal through the element and measuring the resulting volts drop.

Engine Systems

Engine Sensors CFM56-7B

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The T12 sensor is installed through the fan inlet case, at the 2.30 clock position. It consists of a housing and 2 platinum elements. It supplies fan inlet temperature to the EEC for thrust management calculations.

The PT25 sensor consists of a housing and 2 platinum elements. A ram air pressure tube is also included as part of the sensor probe as an option for condition monitoring purposes.

Engine Systems

Engine Sensors CFM56-7B

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Thermocouples are made up of 2 dissimilar metals installed in a sensing probe. In order to measure temperature, they generate an EMF proportional to the difference between a known reference (cold junction) and the sensing probe (hot junction). Located on the combustion case, just behind the fuel nozzles, the T3 sensor measures the temperature of 9th stage air and sends the data to the EEC for use in the fuel

control logic. Its bi-metallic sensor produces a current proportional to the temperature.

Engine Systems

Engine Sensors CFM56-7B

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Eight probes are secured on the LPT case, with their sensing elements immersed in the LPT nozzle stg 2, to monitor T49.5. The sensors are combined into 4 pairs, 2 on each side of the engine. 2 measurements are sent to channel A and 2 to channel B. The T5 sensor is part of the optional monitoring kit and located at the 4 o’clock position, on the LPT rear frame. It consists of a metal body, which has 2 thermocouple probes and a rigid lead carries the signal from the probe to a main junction box.

Engine Systems

Engine Sensors CFM56-7B

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P0 is measured through a vent plug on the EEC pressure manifold. The PS3 sensor is located on the combustion case at 9 o’clock, and provides HPC discharge pressure to the EEC for use in fuel and engine control.

PS13 and P25 are part of the optional monitoring kit available upon customer request. PS13 measurements are processed by channel A and P25 measurements are processed by channel B.

Engine Systems

Engine Sensors CFM56-7B

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The engine is equipped with 2 piezo-electric type accelerometers which can sense and measure vertical acceleration. Both sensors are connected to the AVM, where signals are filtered to identify vibration levels in the LP or HP rotors.

The No1 bearing accelerometer is a 100 pC/g piezo-electric sensor which permanently monitors engine vibration. Due to its position, it is more sensitive to fan and booster vibration but it also reads N2 and LPT vibrations.

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Engine Sensors CFM56-7B

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The FFCCV accelerometer is a solid state assembly installed on the midbox structure at the 3 o’clock position. It is a 100 pC/g piezo-electric sensor.

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