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MECH5725M Aerospace Systems Engineering Assignment 2
Full Mark: 100%
(This is 60% of the final mark of the module.)
Submit your final report in pdf format through Minerva.
Your submission must be written with an Arial 11pt font, using single line spacing
and be no more than 10 pages, excluding the title page. Include all Simulink block
diagrams.
This is an individual assessment, and you are not allowed to discuss or share any
codes, program, diagrams, etc, directly related to the term project assignment.
Similarities in the programming & diagram are to be checked and copies of any part
of source code/diagrams from others are considered as plagiarism.
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The category for this assessment is RED so GenAI tools cannot be used. By
submitting work you confirm that GenAI tools were not used for this assessment.

Part 1
1)
a) At what point in the development process would you begin to define the
requirements [2 marks]
b) What happens to the requirements documents at the End of Life of a
product [4 marks]
c) At what point in the development process are engineering drawings
produced [2 marks]
d) At what point in the development process are systems verified [2 marks]
2) In the process of designing an aircraft cruise speed control system, you are
tasked with selecting the best Airspeed Sensor that is suitable to satisfy the
following requirements: “The aircraft shall be capable of measuring its airspeed with
an accuracy of 0.03 m/s and 95.4% confidence”. Refer to the Airspeed Sensor
options in Table 1 and explain your choice. [5 marks]
Table 1: List of datasheet quoted accuracy for three Inertial Measurement Unit
options.
IMU Accuracy Quoted Accuracy type
Airspeed Sensor 1 0.025 m/s 1-Standard Deviation
Airspeed Sensor 2 0.025 m/s 2-Standard Deviation
Airspeed Sensor 3 0.025 m/s Root Mean Square

Part 2
Use the correct SysML (Systems Modelling Language) elements to draw the
diagrams in the following questions. For this task, you can use the Modelio software
to draw SysML diagrams.
Modelio (https://www.modelio.org/) is a freeware and can be installed on your
computer. You can also use any other SysML drawing software that you may have
access to.
Figure 1: Twin Engine Fuel System Diagram.
1) Draw a bdd (block definition diagram) for the hardware of the fuel system
presented in Figure 1. [10 marks]
Figure 2: Electric Power diagram.

2) Draw an ibd (internal block diagram) for the electric power distribution system
presented in Figure 2, including all signals from/to various components and
subsystems. [10 Marks]
3) Draw the activity diagram (act) for the operation of a fuel jettison system for an
aircraft. [10 Marks]
The jettison system requirements are given as:
The flight crew shall be able to jettison excess fuel in an emergency
situation in order that the aircraft may land under the maximum landing
weight.
The flight crew shall be able to jettison down to a preselected fuel quantity.
The flight crew shall be given indications that fuel jettison is underway.
The flight crew shall be given indications that fuel jettison is completed.
School of Mechanical Engineering, University of Leeds 2024 Page 5 of 9
Part 3
1) You are asked to consider the electrical system in Figure Q2. Each generator is
driven by one Engine and controlled by its own Generator Control Unit (GCU).
Considering that the failure condition of the AC Sync Bus is classified as
Hazardous/Severe, verify whether or not the proposed components in Table 2 allow
the system to meet its safety requirements (i.e. failure rate requirements)
[10 Marks]
Note the following items:
Ignore the availability of a RAT.
Each Generator has its own Generator Control Unit (GCU).
Ignore Circuit Breakers (e.g. APB, GCBs), Tie Breakers (e.g. BTBs) and
Electronic Load Control Unit (e.g. ELCU) failures.
Your answer should include in any logical order that serves your answer:
i. Draw a Dependency Diagram to support your analysis and justification.
ii. Write down your calculations for the total failure rate of the AC Sync Bus.
iii. Does the probability of failure of the AC Sync Bus meets the required safety
objectives
Table 2: Failure rates of electrical system components.
Component Failure rate per flight hour
Engine 1.0×10-7
Generator Control Unit (GCU) 2.0×10-4
Generator 1 (Gen 1) 3.0×10-4
Generator 2 (Gen 2) 4.0×10-4
APU 5.0×10-3

2) You are asked to consider the hydraulic system in Figure 3.
Figure 3: A320 Hydraulic System.
Select the combination of components so that the probability of failure of the Green
Line (i.e. loss of hydraulic power on the Green line) is at 1×10-9 per flight hour or
better. You should minimise the overall cost of the system. [15 Marks]
Table 3 below shows the reliability of hydraulic system components and their costs.
Note the following assumptions:
Each engine can drive one hydraulic pump.
Both engines should have the same engine pump option.
Ignore failures due to leaks.
Ignore Accumulator failures.
Ignore failures due to other hydraulic loads on the hydraulic lines.
The hand-pump is only used on the ground and is not part of this analysis.

Focus on the failures of hydraulic power generation and power transfer
components.
Your answer should include in any logical order that serves your answer:
i. Draw a Fault Tree Analysis (FTA) diagram to support your analysis and
justification.
ii. Select a combination of components that will give the required reliability at the
lowest cost. Justify your design decisions.
iii. Write down your calculations for the total failure rate of the Green line and the
total cost of the components.
Table 3: Failure rates and Costs of hydraulic system components.
Component Failure rate per flight
hour
Cost (￡)
Engine 1.0×10-7 N/A
AC Power 1.0×10-7 N/A
Engine Pump A 2.0×10-4 5,000
Engine Pump B 2.0×10-6 15,000
AC Pump A 5.0×10-4 5,000
AC Pump B 5.0×10-6 10,000
PTU A 1.0×10-4 10,000
PTU B 1.0×10-6 20,000

Part 4
1) Aircraft Subsystem Design
Figure 4: Diagram of heat exchange between aircraft systems.
(i) How can the transition from hydraulic to more electric systems in aircraft
design (i.e. replacing all hydraulic systems with electric ones) impact other
systems shown in Figure 4, and (ii) what steps should designers take to maintain
the desired operational performance of the remaining systems
If additional systems or components are necessary, briefly describe what they
are, how they are powered, and how they would function, using an appropriate
method to explain your proposed architecture. Please provide a response for
both parts (i) and (ii) of the question. [10 Marks]
School of Mechanical Engineering, University of Leeds 2024 Page 9 of 9
2) Design an attitude control system for the twin-engine electric aircraft shown in
Figure 5. [20 Marks]
Figure 5: Twin Engine electric aircraft with conventional configuration.
a) Draw an architecture of the roll and pitch control system. [6 Marks]
b) Explain how the architecture works. Present simple scenarios for how each
subsystem in the architecture functions and interacts with other subsystems
indicating signals, forces, information, etc. [5 Marks]
c) Draw an ibd (internal block diagram) for only the roll attitude control algorithm
including all signals from/to various components and subsystems including
hardware and software subsystems, and components. [6 Marks]
d) Write, using the correct requirement formulation statement structure, 2
functional system requirements for the attitude control system you
proposed. [3 Marks]