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Chapter 8 Engine Control System

1. What are the three main aspects of engine control?

Fuel flow to allow varying engine speeds to be demanded andto allow the engine to be handled without damage by limiting

rotating assembly speeds, rates of acceleration and temperatures.

Air flow to allow the engine to be operated efficientlythroughout the aircraft flight envelope and with adequate safetymargins.

Exhaust gas flow by burning the exhaust gases and varyingthe exhaust nozzle area to provide additional thrust.

2. What are the typical inputs and outputs of an engine control system?

INPUT

Throttle Position-thrust demand

air data

Total temp

Engine speed

engine temp

Nozzle Position

Fuel Flow

Pressure ratio

OUTPUT

Fuel flow control

Air flow control3. Describe the functions of fuel control unit (FCU) of jet engines.

connected to electronic control to allow precise & continous automatic control of fuel flow,in response to throttle.

4. Draw a schematic diagram to show the basic inputs and outputs of an engine control system.

5. Draw a schematic diagram to illustrate a full authority engine control system with electrical

throttle signaling.

6. Describe a typical way of engine speed measurement using a schematic diagram, including how

the engine speed is calculated.

Gearbox mounted speed probe

Exhaust gas temp, by means of thermocouples. Present to pilot as analogue readings incockpit

7. Describe two ways of engine operating temperature measurement.

Chapter 9 Fuel System

1. List typical aircraft fuel system modes of operation.

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2. What are the major components of aircraft fuel system and their functions?

Fuel pumpso Booster pumps used to pump fuel to engineo Transfer pump, used to transferring fuel between a/c fuel tanks

Fuel valves,

level sensors, measure level in particular tanks, prevent over filing Guaging probes, measure fuel quantity on board a/c

3. Discuss advantages and disadvantages of AC and DC fuel quantity management systems.

In an AC system the tank unit information is conveyed by means of an AC voltage modulated by the

measured tank capacitance and therefore fuel quantity.

The problem with the AC signaling technique is that there is a greater risk of electromagnetic

interference (EMI) so that coaxial cables and connectors are required, making the installation more

complex, expensive and difficult to maintain.

In the DC system the probes are fed by a constant voltage/frequency probe drive and utilize automatic

fuel probe diode temperature compensation. Fuel probe signals are rectified by the diodes and the

resulting signal proportional to fuel contents returned to the processor as a DC analogue signalA disadvantage of a DC system is the need for additional components with the fuel tank.

4. Discuss the two common in-flight refueling methods.

Probe and Drougue Methodo Multiple a/c cab be refuelledo basket has greater history of causing damage to a.co lower fuel flow

Flying Boomb methodo higher fuel flowo only one a/c at a time

Chapter 10 Hydraulic System

1. Discuss the major advantages of aircraft hydraulic actuation in comparison with electrical motors.

Electric motor cant match power to weight ratio of gydrualic actuator, particually above 3kW

Hydraulics meets low weight, low volume, low inital cost, high reliability, low maintainence2. What are the main components of an aircraft hydraulic system? Explain their functions.

Reservoir-ensures sufficient fluid is aviable under all conditions

Heat exchanger

filter

pumpcause a flow of fluid at certain pressure

gearbox-connected to hydraulic pump, primary source of power

actuator

accumulator

demand signals

3. Describe the operation of principle of hydraulic pumps.

sense outlet pressure and feed back this signal to play carrying reciprocating pistons

4. Discuss the design procedure of hydraulic piping.

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separate pipes to avoid common mode failures as result of accidental damage

measure lengths of pipe to calculate flow rate in each section

press drop of less than 25% selected, this may be divided between pressure pipes, returnpipes

5. Discuss aircraft hydraulic system fluid conditioning.

Fluid needs cooling and cleaning Heat exchange is sued for cooling, provided when a/c is in flight

Servo-valves with fine clearances emphasize need fo clean fluids

Filter elements and wire mesh are able to withstand pressure