Aerospace systems (copy)

Systems

A set assembled from a number of subsystems or individual components connected to each other, and capable of treating physical matter, energy, or information, in order to meet the purpose or number of purposes

Systems Engineering

A holistic interdisciplinary management process, aimed at evolving a lifecycle balanced set of system solutions which satisfy customer needs.

Pyramid of systems (Fill in blanks from top to bottom)

Enterprise, System of Systems, System, Subsystem, Components

Factors influencing system design

Advancement in technologies, Competition, Specialization

Principle of systems thinking (two terms)

Hierarchy, Viability

System engineering problem solving STEP 1

Understand the Problem context

System engineering problem solving STEP 2

Identify and Understand the problem

Structure of Systems Engineering 1

SE Management

Structure of Systems Engineering 2

Requirements and Architecture definition

Structure of Systems Engineering 3

Development of subsystems

Structure of Systems Engineering 4

System integration and Verification

Lifecycle

The evolution with time of a System from idea to disposal

Lifecycle Stage

An identified Objective in the Life of a system, used to manage the resources and activities of a project

Lifecycle proccess

A squence of tasks needed to achieve a defined goal, within the objectives of a lifecycle phase

Generic process model (1st one)

Waterfall model

Process interdependencies in V model (one example)

Systems architecture and system integration

System Design Methodology (3points)

Initiation of creative processes, Envisage all elements needed for system design, Assurance that the design has appropriate consequences on environment and society

Two types of Customer needs

Direct, Latent

Types of Systems Architecture (two types)

Integral, Modular

Two methods used for Concept design

Traditional Brain storming, Brain ball method

Aerospace system

Systems used on board and aircraft or spacecraft

on-board Aerospace system (4)

Hydraulic, Pneumatic, Electrical, Landing gear

How do we classify Aerospace systems? (from perspective of safety)

Primary, Secondary, Auxiliary

What are the design specs for Aerospace Systems? (+ give an example)

Qualitative and quantitative definition of system functions, Definition of environmental characteristics, Maintainability. Example = Temperature

What are the most important constraints for the design of the Aerospace systems? (example)

Weight, Available Volume (in terms of fuel systems)

What does a Functional diagram represent?

It represents the functions performed by system components

Name a technical drawing type

Drawing of parts

Name all the quantities defining power

Mechanical (velocity), Mechanical (Angular velocity), Electrical (Voltage), Fluid-Hydraulic (Pressure), Fluid-Gaseous (specific Enthalpy)

Name an on-board system and the type of power it consumes

On-Board lights, electrical

What is the viscosity of a fluid?

Represents the fluids resistance to flow

What is dynamic viscosity?

Measure of a fluids resistance to flow when an external force is applied to it

What is kinematic viscosity?

Dynamic viscosity per unit density

What is vapour pressure?

a measure of the volatility of a liquid

What is the 'Flash point' of hydraulic fluid or fuel?

the lowest temperature where a fluid evaporates enough to burn if ignited

What is 'Auto-ignition point'?

the lowest temperature when flame is generated in presence of air, with no external ignition.

What is compressibility of fluid

the property of a fluid to change volume when subjected to changing pressure

What is the bulk modulus? (give the unit)

a measure of compressibility, Psi

What is 'effective bulk modulus?'

Bulk modulus that considers gas in the system

Define Pascal's Principle

pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of the container

What is the 'pressure drop' phenomenon?

when a fluid flows in a pipe of constant section and height, with no exchange of energy with the external world, it anyway decreases its pressure

What is Reynolds number?

a dimensionless number used in fluid mechanics to indicate whether fluid flow past a body or in a duct is steady or turbulent

What is the 'hydraulic diameter'?

the cross-sectional area of the channel divided by the wetted perimeter

For turbulent flow, friction coefficient is a function of which parameter?

mean flow velocity

What is the 'loss coefficient'?

measures the minor loss to the change in velocity due to friction through pipes, fittings, and valves

What is the purpose of hydraulic systems?

Transformation, distribution and utilization of mechanical energy through the use of incompressible fluid at high pressures

What type of hydraulic device generates and maintains pressure inside hydraulic system?

pumps, valves, hydro-accumulators

What are the main positive aspects of Hydraulic Systems? (3 points)

high efficiency of the power transmission, ability to withstand overloads without damage, high reliability

Which aircraft systems are powered by hydraulics? (2 examples)

Flight controls, Airbrakes

What are the advantages of high pressure hydraulic installations?

smaller size of actuator/cylinders for the same level of power/force required, less weight

Which types of pump works on fluid-dynamic principle? (2 examples)

centrifugal, axial

Which type of volumetric-positive displacement pump you know? (2 examples)

rotary, reciprocating

What is the required number of pistons for smooth operation of piston pump? (numerical range)

7-9

How operating pressure affects the flow capacity of positive displacement pumps?

Flow rate decreases due to loss of volumetric efficiency as the pressure increases (variation is small)

Why should we keep pressure constant in hydraulic systems?

the system control is based on regulating the constant pressure in the installation

What are the methods of flow regulation for volumetric pumps?

Pump with constant delivery with a regulator valve, Pump with variable flow delivery

What is the purpose of piping in on-board aerospace hydraulic systems?

Distribution of flow and pressure

What is the role of hydraulic accumulator?

short emergency operation, damping of pressure fluctuations

What types of hydraulic accumulator you know?

Spring, Direct gas-fluid, gas-piston, gas-diaphragm, gas-bladder

Name two types of hydraulic actuators?

Spring, gas-piston

What is purpose of heat exchanger in hydraulic system?

control temperature, and therefore viscosity

What is function of relief valve?

control pressure in a system

What is function of check valve?

Prevent backflow

What is purpose of hydraulic distributor?

Regulate the flow of a fluid

Which on-board systems use pneumatics? (2 examples)

Air conditioning, defrosting

What is the main source of air for pneumatics, and where it comes from?

Bleed air (air from jet engine)

What is purpose of a compressor, explain how compressor works?

Transforms mechanical energy into potential energy (air pressure). Uses kinetic energy of the rotor to slow the flow of a fluid and therefore increase pressure

What is purpose of a turbine, explain how turbine works?

extracts energy from fluid flow and converts it into useful work. airflow moves the turbine blades which transfers energy to a rotor

How should we start a main aircraft jet-engine with pneumatic system?

with a burst of compressed air on the jet-engine turbine

What is purpose of wheels in lending gear assembly?

Support for the tire, connections for bearings axle and brakes

What is purpose of brakes in wheel assembly, and how they function?

Provide slowdown and stopping of the aircraft during landing and taxiing

What type of brakes you know? (2 types)

Drum brakes, disc brakes

What are the main components of Disk Brakes?

Rotor disc, Stator disc

How disk brakes functioning?

The brakes act by introducing a friction torque which tends to slowdown the rotation of the wheel

What materials are used for making disk brakes rotors and stators?

combination of steel and composite carbon base materials

How brakes Anti-Blocking System (ABS) works on aircraft?

avoid wheel locking by modulating the braking system pressure

What are the main parameters we should know in order to estimate how much airplane kinetic energy on lending is dissipated by the brakes?

riving torque, brake torque, tangential or horizontal force on the ground, friction torque

Which aircraft systems use the electrical power as the energy source?

Navigation instruments, cabin lighting, navigation lights, anti-ice protection

What are the electrical power sources on board of the aircraft? (6 sources)

Main aircraft engines, A.P.U, connection with ground network, Pneumatic engines, R.A.T, batteries

How we can convert AC to DC?

AC to DC conversion with Transformer Rectifying Unit TRU

How we can convert DC to AC?

DC to AC conversion with static inverters

How we can store electrical power on board of the aircraft?

Batteries

What types of the batteries you know? (4 types)

Pd, Ni-Cd, Ag-Zn, Li-Ion

How we can prevent electrostatic charges to damage the aircraft? (3 points)

establish electrical continuity between all the external structural elements of the aircraft, introduce electrical charge sinks, aircraft grounding at landing

What is stands for "Ram Air Turbine"?

a small turbine that is installed in an aircraft and used as an alternate or emergency hydraulic or electrical power source

Name one component of Aircraft Electrical System: Generation

Stator

Name one component of Aircraft Electrical System: Regulation

Alternator

Name one component of Aircraft Electrical System: Distribution

Cabling

Name one component of Aircraft Electrical System: Auxiliary Systems

Terminals

Name one component of Aircraft Electrical System: Utilization

Switches

What is the voltage + frequency of AC current used on aircraft?

115/270V, 400Hz or variable

What is the voltage of DC current used on aircraft?

28V

What does IDG stand for?

Intergraded drive generator

Name the flight control surface required to produce pitch

Elevators

Name the flight control surface required to produce yaw

Rudder

Name the flight control surface required to produce roll

Ailerons

What are the Primary Flight controls?

Control of aircraft movement around the principal axes of inertia

What are the Secondary Flight controls?

Flaps, spoilers, airbrake, engine control-thrust reversers, landing gear extraction-retraction

Which combination of the control surfaces represents: Elevon?

Elevator, Aileron

Which combination of the control surfaces represents: Flaperon?

flaps, ailerons

Which combination of the control surfaces represents: Taileron?

Elevator+ Aileron on tail