CHAPTER 70s CMF56 Flashcards by Anthony Devlin

How many engine drains are fitted to the CFM 56?

It is composed of 4 drain collectors with manual drain valves for trouble shooting and 2 holding tanks.

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How far can the Thrust reverser cowl doors be opened to and what flying control dictates this?

The thrust reverser half doors can be opened to a 45 degrees position for engine removal. In this instance if the inboard Cowl is opened to 45°, the wing slats have to be in the retracted position. For normal access to the engine core components, the thrust reverser half doors can be opened at 35 degree with the slats in extended position.

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High Pressure Compressor (HPC) inlet is at what engine station number?

STA 25

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What is max N2 percentage?

The overspeed governor system limits the core engine speed (N2) to a maximum of 106%, in the event of a malfunction that could drive the engine into an overspeed condition.

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How could the HP fuel SOV cause an engine FAULT light to come on?

The HP fuel SOV is monitored by two microswitches which send signals to the ECU and then to the Engine Interface Unit (EIU). In case of disagreement between control and position, an ECAM warning is triggered and the engine FAULT light comes on.

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How is N1 speed controlled?

The FMV is controlled by the Electronic Control Unit (ECU) to obtain
the desired N1, selected either by the thrust lever or the Auto Thrust
System.

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How is the IDG oil cooled?

The fuel bypassed from the HMU and returned from servos is used to cool the IDG oil through the IDG oil cooler. The fuel then returns to the fuel pump inter-stage and re-circulates through the system.

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How is the Low Pressure (LP) fuel Shut-Off Valve (SOV) controlled?

The Low Pressure (LP) fuel Shut-Off Valve (SOV) operation is controlled from the engine fire panel or from the engine start panel.

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In normal conditions how is the engine ECU electrically powered?

Each ECU is powered by a three-phase permanent magnet alternator
when the engine N2 > 58% (15%). The FADEC Control Alternator provides an independent power supply to both ECU channels.

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How is the Active and the Stand-by Channel alternation determined?

The ECU can detect and isolate failures using the BITE system. The BITE system allows each ECU channel to determine its health status. The healthier channel is selected as the Active Channel. The other one is the Stand-by Channel. When both channels have the same health status, Active and Stand-by Channel selection alternates after
every engine start.

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What is Fail Safe Control in a FADEC?

If one channel is faulty, and the channel that is in control cannot ensure an engine component function, the component is moved to a fail-safe position.

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What is the power supply for the No1 engine EIU?

2 x 28VDC from the DC ESS BUS & BAT BUS

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What is the power supply for the No2 engine EIU?

2 x 28VDC from the DC ESS BUS & DC BUS

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Engine LP Fuel Shut-Off Valve (LP SOV) control by the ENG FIRE P/B will operate ……….

When the ENG FIRE P/B is released out, 2 electrical motors drive the LP SOV to the closed position.

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Engine LP Fuel Shut-Off Valve (LP SOV) control by the MASTER Lever closure command will operate ……….

When the MASTER lever is set to OFF, both electrical motors drive the LP SOV to the closed position. The closure of the pressure raising and SOV is controlled directly from the MASTER lever. When it is set at the OFF position, it energizes the latching torque motor which closes the valve. A time-delay relay automatically de-energizes the pressure raising and SOV latching torque motor 2 minutes after engine shutdown. This device avoids damage due to high temperature induced by a long time power supply on ground.

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During Auto start when does the starter valve cut out?

When N2 reaches 43%, the EEC closes the starter valve and cuts off the ignition.

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What are the starter limitations?

1, 4 consecutive cycles, each of 2 minutes maximum duration. 2, 20 seconds of non operation between cycles. 3, after 4 cycles, wait 15 minutes before attempting a new start. 4, No running engagement of the starter when N2 is above 20%.

If the starter Shut Off Valve (SOV) does not open, how would this be displayed on the flight deck?

If the starter Shut-Off Valve (SOV) does not open, an aural warning
sounds, the MASTER CAUTion and engine FAULT lights come on and
an ECAM message appears.

If there is an ignition fault in automatic mode, how would the ECU respond?

In this failure case the ECU will automatically do 2 start attempts. 1, 1 normal start.
2, 1 additional attempt.

What is the sequence for a failed engine start in auto start?

1, The engine rotates.
2, One ignitor is automatically turned ON at 16 % of N2.
3, Fuel is automatically supplied at 22 % of N2.
4, If engine light-up is not obtained within 15 seconds, the FADEC
automatically turns the ignition and the fuel OFF and dry cranks the
engine for 30 seconds
5, Before initiating automatically a new start. An aural warning sounds, the MASTER CAUTion light comes on and an ECAM message appears.

What is the maximum EGT during start?

The ECU monitors the EGT and N2, according to their schedules, to
provide the correct fuel flow. The maximum EGT during start sequence is 725º C.

The CFM56-5B can power all aircraft types of the Single Aisle family. CFM56-5B engines are available in several thrust ratings. How is the thrust rating set?

A programming plug on the Electronic Control Unit (ECU) changes the available thrust.

What loads does the forward mount carry?

The forward mount carries the engine thrust, vertical and side loads.

Which bearings are contained in the forward sump?

The forward sump is in the fan frame and is the location of bearings No.1, No.2 (fan/booster shaft) and No. 3 (High Pressure (HP) shaft).

What is the main operation of the Variable Bleed Valve system?

The VBV system controls the airflow from the fan and the booster to the High Pressure Compressor (HPC) by using 12 valves. By dumping excessive air into the fan air stream, the VBVs increase the booster mass flow and improve the booster and the HPC matching at low speed and transient operations.

What is the main operation of the What is the main operation of the Variable variable stator vane system?

The VSV system controls the primary airflow through the HPC by varying the angle of the Inlet Guide Vanes (IGVs). The VSVs give aerodynamic matching of the LP stages of compression with the HP stages to prevent engine surge.

What is the function of the Variable Bleed Valve (VBV) system?

The function of the Variable Bleed Valve (VBV) system is to regulate the amount of air discharged from the booster into the inlet of the HPC. To eliminate the risk of booster stall during low power conditions.

What are the thrust limit modes?

1, Climb (CL) 2, Flexible Take Off 3, Maximum Continuous Thrust (FLX/MCT) 4, Take Off Go Around (TOGA) 5, Reverse mode limit (MREV).

On the ground with the engines running the displayed N1 rate limit is always what mode?

On the ground with the engines running the displayed N1 rate limit corresponds to the TO/GA thrust limit whatever the thrust lever position is.

What 2 inputs are required for the ECU to compute an N1 rating limit?

N1 rating limit is computed by the ECU according to Thrust Lever Angle (TLA) and the air data parameters from the Air Data Reference (ADR).

Where is the engine vibration indication and how do you get access to this information?

The engine secondary monitoring parameters are displayed on the ECAM lower SD when it is selected manually or automatically.

If the thrust reverser is mechanically locked out for dispatch what will be displayed on the flight deck?

If there is a mechanical inhibition of the thrust reverser (for dispatch), a caution "ENG X REV INHIBITED" is displayed on the ECAM to tell the crew that the thrust reverser is inoperative.

Can the aircraft be dispatched with a failure of the FUEL CLOG warning on ECAM?

In case of a failure of the FUEL CLOG warning on ECAM, the aircraft may be dispatched per MEL as long as the fuel filter is changed once each day.

What operation will follow a (maximum 15 seconds) wet crank?

After the reset of the ECU, the ECU will command the starter SOV to open when the N2 speed is less than 10%. The dry CRANK procedure is initiated. Continue to dry crank the engine for 60 seconds (within the starter limitation of 2 minutes on), this will dry the fuel that can be in the combustor.

How is the scavenge oil cooled before returning to the oil tank?

The scavenge oil flows through a master chip detector, then is cooled through the servo fuel heater and the main oil/fuel heat exchanger before returning to the oil tank.

If there is an electrical failure of the start valve, can the aircraft be dispatched?

In case of an electrical failure of the start valve, the valve may be operated manually to start the engine. The aircraft may be dispatched per the MEL with the valve INOP closed.

If operating the engine start valve manually what safety precautions must be observed?

Do not operate the valve unless the starter system is pressurized. Damage to the valve can occur.

When is Thrust Reverse available?

With a Throttle Lever Angle (TLA) lower than -3º, the SOV opens if the altitude is less than 6 feet and if high forward thrust is not selected on the opposite engine. Then the HCU is supplied hydraulically for door deployment.

What prevents initial deployment of the Thrust Reverser?

A Pressure Switch in the HCU gives a feedback signal to the ECU. The four actuators are initially pressurized on the rod side of the pistons keeping the doors in the stowed position.

How is the deployment of the Thrust Reverser controlled?

The ECU energizes the solenoid of the directional valve. The four hydraulic latches at the pivoting door open sequentially. Only when all four latches are open the hydraulic pressure pushes on the head side of the hydraulic actuators. The pivoting doors open. The stow and deploy switches are used to monitor the pivoting door position and for ECU control.

With the aircraft on the ground, how can a thrust reverser test be performed?

A thrust reverser test can be performed through the MCDU menus. During this test, the Centralized Fault Display and Interface Unit (CFDIU) simulates engine running (N2 condition) to permit the thrust reverser deployment.

How is the engine oil supply pump pressure controlled?

The supply pump pressure is not controlled, but the oil output flow is, by design, always greater than the lubrication requirements. A pressure relief valve bypasses part of the output flow to protect the supply pump against abnormal output pressure build-up.