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.

Generative AI (Gen AI)

There is a three-tier traffic light categorisation for using Gen AI in assessments: red, amber and green. The Categories of assessments information, provides further details. This includes information on taking a critical approach to the use of any output from a Gen AI tool. The strengths and weaknesses of Gen AI guidance provides further information.

The category for this assessment is RED unless an exception is explicitly mentioned in the question. 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? [1 mark]

b) What happens to the requirements documents at the End of Life of a product? [2 marks]

c) At what point in the development process are engineering drawings produced? [1 mark]

d) At what point in the development process are systems verified? [1 mark]

2)

What are the main challenges encountered in Model-Based Systems

Engineering (MBSE) according to recent literature? Support your analysis with references from the last five years. Additionally, propose a simple and effective tool or method to address one of these challenges.

(Limit your response to one page.) [10 marks]

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. [5 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.

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 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	1.0x10-7
Generator Control Unit (GCU)	2.0x10-4
Generator 1 (Gen 1)	3.0x10-4
Generator 2 (Gen 2)	4.0x10-4
APU	5.0x10-3

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 1x10-9  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	1.0x10-7	N/A
AC Power	1.0x10-7	N/A
Engine Pump A	2.0x10-4	5,000
Engine Pump B	2.0x10-6	15,000
AC Pump A	5.0x10-4	5,000
AC Pump B	5.0x10-6	10,000
PTU A	1.0x10-4	10,000
PTU B	1.0x10-6	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]

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,

functional system requirements for the attitude control system you proposed. [3 Marks]