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1. Analyse and formulate the requirements in the following questions.
a. In the process of designing an aircraft stability control system, you are tasked with
selecting the IMU (Inertial Measurement Unit) that is suitable to satisfy the following
requirements: “The aircraft shall be capable of measuring its roll and pitch with an accuracy
of 0.01° and 95.4% confidence”. Refer to the IMU options in table Q1.1 and explain your
choice. [5 marks]

Table Q1.1: List of datasheet quoted accuracy for three Inertial Measurement Unit options.
IMU Accuracy Quoted Accuracy type
IMU1 0.009° 1-Standard Deviation
IMU2 0.01° Root Mean Square
IMU3 0.01° 3-Standard Deviation
b. Given a piston head diameter of 5 cm and a stroke of 0.5 m. What is the minimum
pressure and volume flow rate that should be used by the hydraulic system in order for the
piston to exert 10 kN of force while traversing the length of its stroke in 10 seconds.
Write the hydraulic system requirements for the pressure and flow rate. [5 marks]
c. Given the following mission statement: All models of car X have to be able to
automatically detect road markings and automatically stay in lane. Write 2 functional system
requirements that conform to this mission statement. [5 marks]
d. Select and justify the most appropriate fuel pump from table Q1.2 below to satisfy the
following requirements:
? The fuel pump shall be able to provide a constant displacement of 10 L/rotation.
? The fuel pump shall be able to operate at shaft speeds of up to 6000 RPM.
? The fuel pump should be able to operate at a pressure of 200 psi. [5 marks]

Table Q1.2: Performance data for three fuel pump options.
Displacement Rate
in L/revolution
Maximum rotation speed in
Revolution Per Minute (RPM)
Maximum
Pressure in psi
Pump1 10 7500 180
Pump2 9 8500 280
Pump3 10 5000 210
e. A satellite active thermal control system is using a 2 cm2
radiator with an emissivity of
0.95. In nominal operation the electronics components consume 250 mW of electrical
power. Assuming the satellite is eclipsed by the Earth (there are no solar or albedo
radiation affecting it) and consider the radiator is pointing towards Earth which has an
average temperature of 10°C. [5 Marks]
i. Assuming perfect heat transfer between the electronic components and the radiator,
and that all the energy consumed by the electronics is converted to heat, what is the
temperature of the electronics in nominal operation? Show your full calculation steps.
ii. The electronics maximum operation temperature is 160 °C; is this requirement met
when the satellite radiator is pointing towards Earth when passing in its shadow?
Ref: ME20214G74-5
MECH5765M01

2. Use the correct SysML (Systems Modelling Language) elements to draw the diagrams in
the following questions.
a. Draw a bdd (block definition diagram) for an electric FW UAV (Fixed-Wing Unmanned
Aerial Vehicle with wing-tail configuration) roll and pitch attitude control system including all
hardware and software subsystems, and components. [13 marks]
b. Draw an ibd (internal block diagram) for the FW UAV (Fixed-Wing Unmanned Aerial
Vehicle with wing-tail configuration) roll attitude control algorithm including all signals
from/to various components and subsystems including hardware and software subsystems,
and components. [12 Marks]
Ref: ME20214G74-5
MECH5765M01

3. Analyse the fault consequences and calculate the subsystem reliability in the following
questions.
a. Using the A320 hydraulic system diagram shown in Figure Q3.1 below analyse the
independent cases below: [8 Marks]
i. Case1: Engine 2 fails. Describe in detail all the possible alternative options for
powering the Rudder and Right Spoiler 4.
ii. Case2: The PTU fails and causes a leak in both the yellow and green lines. Write
down all control surfaces that are still available be used for controlling the roll of the
aircraft and specify the line and source of hydraulic power.
Figure Q3.1: A320 Hydraulic System.
Ref: ME20214G74-5
QUESTION CONTINUES ON NEXT PAGE
MECH5765M01
b. You are asked to consider the electric generation system for a twin-engine aircraft. Each
engine can drive up to two generators simultaneously. Table Q3 below shows the reliability
of 3 available electric generators and their cost.
Design a main electric generation system for the aircraft with the probability of failure of the
essential bus required to be at 1×10-9 per flight hour or better. You should minimise the
overall cost of the system. [17 Marks]
Note the following items:
? Ignore the APU, RAT, and batteries.
? Both engines should have the same generator configuration, e.g. in the case of
selecting one generator per engine, both engines will have the same selection.
Whereas when selecting two generators per engine (see Figure Q3.2) Generator 1
should be the same option as Generator 3 and Generator 2 should be the same
option as Generator 4.
? The architecture diagram in Figure Q3.2 shows the configuration of using a
maximum of 4 generators.
Your answer should include:
i. Proof that using one generator per engine will not meet the reliability requirement.
Show your full calculation steps and the relevant diagrams that aided in this
calculation.
ii. Select a combination of generators that will give the required reliability at the lowest
cost. Justify your design decisions.
iii. Draw a Fault Tree Analysis (FTA) diagram of the designed configuration to support
your analysis and justification.
iv. Write down your calculations for the total reliability of the system.
Ref: ME20214G74-5

Table Q3: Failure rates and Costs of power generation system components.
Component Failure rate per flight hour Cost (￡)
Engine 1.0×10-7 N/A
Generator Control Unit (GCU) 5.0×10-4 N/A
Generator A 8.0×10-3 5,000
Generator B 4.0×10-4 15,000
Generator C 5.0×10-9 40,000
MECH5765M01
Figure Q3.2: Power Generation Architecture.

4. Electric Aircraft Subsystem Design
a. Design a cruise speed control system for the twin-engine electric aircraft shown in Figure
Q4. [8 Marks]
i. Draw the architecture of the cruise speed control system.
ii. Explain how the architecture works.
b. Select the most appropriate type of actuator to deploy the primary control surfaces of this
aircraft. [10 Marks]
i. Identify the appropriate actuator type.
ii. Justify your decision.
iii. Explain the principle of operation of the chosen actuator.
c. Given that the primary electric power source on-board this aircraft is a bank of 270 V DC
batteries and that the main fan engine motors run on 115 V AC. Draw the simplest power
distribution system that allows you to power 115 V AC loads, 28 V DC loads, and 270 V DC
loads. [7 Marks]
Ref: ME20214G74-5

Figure Q4: Twin Engine electric aircraft with conventional configuration