Aerospace System Flashcards
quizzes quesions
What’s the definition of a
system?
Its a set, assembled from a number of sub-systems
or individual components, capable of treating
physical matter , energy or information in order to
meet a specific purpose.
What’s the definition of systems
engineering?
Systems engineering is a holistic, interdisciplinary
management process aimed at evolving system
solutions to satisfy consumer/user needs.
What is the Pyramid of Systems
Hierarchy?
A visual pyramid diagram describing how systems
are created.
An ‘enterprise’ at the top
‘Systems of systems’ near the top
‘System’ in the middle
‘Components/subsystems’ at the bottom
Name some factors which
influence the development of
systems engineering:
1.) Advancement in technology: Creates new
opportunities but also induces more development
risk
2.) Competition: Drives seeking superior solutions,
often at trade offs too.
3.) Specialization: Requires breaking a system into
components corresponding to user needs.
Name any two principles of
systems thinking:
Hierarchy, viability, completeness, emergence,
boundary, holism
Name any two systems
engineering problem solving
steps:
1.) Understand the problem context
2.) Identify and understand the problem
3.) Generate potential solution options
4.) Implement the chosen solution
5.) Review the success of said system
Name all four elements that
make the ‘’ Structure of
Systems Engineering’’ :
S.E Management (planning / organization )
Requirements and architecture definition
Development of sub-systems
System integration and verification
What is the 1. Lifecycle 2.
Lifecycle stage and 3. Lifecycle
process?
- Lifecycle : Evolution of a system through time.
From concept to disposal entirely. - Lifecycle stage : An identified objective within the
systems life, used to manage resources and
activities of a project. - Lifecycle process : A sequence of tasks needed
to achieve a defined goal WITHIN a lifecycle phase.
Name any generic process
model.
Waterfall model
v- model
Spiral model
Spiral to circle model
What is the difference between
Process order and Process
dependency , when applied to
a lifecycle model?
Process order = The order processes must occur
when designing a successful system
Process dependency = What a process depends on
for its design
What are the process
interdependencies contained
within the ‘ V ‘ Model?
(user testing) Requirements and concepts <—–> Demonstration
and validation.
(system testing) Architecture and specification <— > Integration and
verification.
(Integration system)Design <——> Testing
Discuss the difference between
a lifecycle stage and lifecycle
process
A stage is an identified objective within the lifecycle,
whilst a process contains the sequence of tasks
needed to reach a goal, within a lifecycle stage.
Discuss the difference between
a technical process and a
project process
Technical processes relate to the application of
system problem solving, whilst project processes
ensure viability of a lifecycle stage.
Discuss the difference between
a lifecycle model and a project
A lifecycle model aims to deal with problems which
affect the lifecycle , whilst a project is the
overarching idea and work needed to achieve
everything.
What is the relationship
between system levels and
project relationships.
System levels show the connected order of system
design, and project relationships are used to define
these system levels
What is ‘’ System design
methodology’’
Its a path needed to achieve 3 primary objectives :
1.) Initiation of creative processes for achieving
novel and innovative solutions of lasting relevance
2.) Envisage all necessary system design elements
3.) Assurance that design has appropriate
consequences on the environment and society
throughout its lifecycle
Name any two types of
Customer needs:
Direct needs
Latent needs
Constant needs
Variable needs
General needs
Niche needs
What represents the ‘’ House of
Quality ‘’?
A ‘ product planning matrix’ which shows how
customer requirements relate to ways /methods
designers can achieve those requirements.
What types of system
architecture can we
recognize?
Integral type : Each tool performs one task
Modular: Architecture contains sub-structures which
correspond to subsets of the system functional
model.
Name any two methods used
for concept design?
Brain storming
Brain ball method
C-Sketch/ 6-3-5 method
TRIZ ( Theory of inventive problem solving )
Morphological analysis
Define the meaning of an
Aerospace System
A collection of components which connect substructures together to fill a specific task. Eg Landing
gear, air conditioning, flight controls, emergency
systems, fuel systems, hydraulic/pneumatic systems.
Name any 4 on board
aerospace systems
Landing gear, air conditioning, flight controls,
hydraulic/pneumatic systems
From the perspective of safety
and mission success, how can
we classify aerospace
systems?
Primary systems -Failure can lead to safety
compromises
Secondary systems: Failure can degrade
performance but doesn’t compromise safety
What are the design
specification for aerospace
systems. Give an example too
A design specification is a parameter you need to
keep in mind when designing your system.
Example : Fuel systems requires fuel volume
knowledge, pressure and flow knowledge too
What are the most important
constraints for the design of an
Aerospace system?
Weight is #1 constraint.
Center of gravity, available volume, material limits
What represents the ‘’
Functional Diagram’’ of the
system?
A block diagram representing the function
performed by system components , and the
processes to make that function happen
Name any type of Technical
drawing?
Part, component, system or sub-system assemblies.
Name all quantities defining
power (mechanical, electrical,
fluid-hydraulics, fluid pneumatics) , and provide the
equations.
Velocity (mechanical) : P=vF
Angular velocity (mechanical) P=omega*M
Voltage (Electrical) P=IV
Pressure ( Fluid hydraulic ) P=pQ
Specific enthalpy ( Fluid- gaseous ) P=h * dm/dt
Name any On-board
Aerospace system and which
type of power it consumes.
Fuel system- Uses Electric and Pneumatic systems
What is fluid Viscosity?
The fluids resistance to flow.
What is dynamic viscosity
measure of the molecular “stickiness” between
layers of a fluid
What is vapor pressure?
a measure of the force exerted by a gas above a
liquid
What is the flash point of fuel?
The lowest temperature when if ignited, a fluid
evaporates enough to burn a flame.
What is the Auto-ignition
point?
Auto-ignition point is the lowest temperature when
flame is generated in presence of air, with no
external ignition.
What is compressibility?
a measure of how much the volume of matter
decreases under pressure
What represents the Bulk
modulus and what’s its units?
How resistant to compression a substance is .
(Pascals)
What is the effective bulk
modulus?
This is the bulk modulus, but also considering
concentrations of air/vapor within the substance
too
Define pascals principle:
Pressure applied to a fluid in a closed container is
transmitted equally to every point of the fluid and to
the walls of that container (Nelly the dinosaur from
fluid mechanics year 1)
What is kinematic viscosity?
ratio of dynamic viscosity to density
Whats the pressure drop
phenomenon?
Due to frictional forces, the pressure doesn’t remain
constant through pipes.
What is Reynolds number?
A unitless number indicating whether flow is
laminar or turbulent.
Whats the hydraulic diameter
4A/P , A = area of pipe, P = perimeter
What’s the friction coefficient?
A coefficient accounting for frictional losses in
pipes
For fully turbulent flow, the
friction coefficient is a function
of which parameter?
Reynolds number, but also relative roughness
What represents the ‘(head)
loss coefficient’
Losses of energy due to sudden sharp geometry
changes.
Describe the phenomenon of
‘‘Water hammer’’
Its an overpressure caused by the rapid closure of
valves
Whats 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?
Pumps and valves
What are the main positives of
hydraulic systems?
high reliability
ease of control
reduced maintenance requirements
What aircraft systems are
powered by hydraulics?
Airbrakes, flaps, rudder, elevators, ailerons
What are the advantages of
high pressure hydraulic
instalations?
You can use smaller actuators and cylinders
Reduced component weight
Smaller component volume
Name some types of
volumetric positive
displacement pump
gear pumps, lobe pumps, membrane pumps
Which types of pump work on
the fluid-dynamic principle
centrifugal, axial, hydraulic shock pumps
How many pistons are needed
for a smooth piston pump?
7-9
How does operating pressure
affect the flow capacity for a
positive displacement pump?
As pressure increases, flow decreases.
Why should we keep pressure
constant in hydraulic systems?
Sizing of the actuators is based on constant
pressure
No interference between multiple hydraulic
motors/actuators.
Name a method of flow
regulation for volumetric
pumps?
A variable flow delivery to the pump
Whats the purpose of hydraulic
systems piping
Distribution of flow and pressure from
generators(pumps) to consumers (actuators or
hydraulic motors).
Whats the role of a hydraulic
accumulator
Used to damp pressure fluctuations
Name some types of hydraulic
accumulator
Spring, gas fluid, gas piston, gas bladder
Name 2 types of hydraulic
cylinders-actuators?
Single acting, unbalanced
Double acting, unbalanced
Tandem, balanced
Telescoping
Whats the purpose of a heat
exchanger in a hydraulic
system?
To transfer heat from the high temp pressure area,
elswehere
Whats the function of a relief
valve?
Opens in case of excess pressure, stopping system
damage
Whats the function of a check
valve?
Allows one directional flow
Whats the purpose of a
hydraulic distributor?
They determine the flow direction within a hydraulic
system.
Which on-board systems use
pneumatics?
Aircon
De-icing
Defrosting
Fuel transfer
Fuel tank ventilation
Wha’ts the main source of air
from pneumatics, and where
does it come from
Bleed air from the jet engine compressor. Air is
taken from the 2nd, 5th and 6th compressor stages
What is the purpose of a
compressor and explain how it
works
Theyre used to increase the pressure and
temperature of the air, before the combustion
chamber stage.
What is the purpose of a
turbine and explain how it
works.
Turbines extract energy from the fluid flow, and
converts it to useful work out.
How should we start a main
aircraft jet-engine with a
pneumatic system
A burst of compressed air on the jet engine turbine
from the APU starts the cycle. Batteries are used to
work the APU.
Name all landing gear
components which
absorb/dissipate impact
energy upon landing
Tires
Wheels
Brakes
Wheel assembly bogie
Strut and shock absorber
What are the limits for
permissible vertical
component for landing gear
speed?
around 2m/s
Describe the working principle
of a landing gear shock
absorber
They essentially convert kinetic energy to thermal
energy, and then dissipate that to the atmosphere.
Basically oil pumps, where pistons work against
hydraulic fluid to form pressure
Name some types of shock
absorber
Coil spring type
Rubber pad type
Deformable leg leaf spring type
What are the values for landing
gear shock absorber stroke
2-8 inches typically, depending on aircraft size
Whats the purpose of wheels
in the landing gear assembly?
They support the tire
Whats the purpose and
function of landing gear brakes
They slow down and stop the aircraft during taxiing
What are the main components
of disc brakes and how do disc
brakes function
Rotor disc
Stator disc
Brake assembly
Friction occurs between the rotor and stator disc,
and hence creates braking torque.
What materials are used for
making disk brake rotors and
stators
Combination of steel and composite carbon based
materials.
Used to be beryllium alloys and steel
How much energy is typically
absorbed by the brakes?
Multiple millions of Newton-Meters worth of energy
How can you estimate the
kinetic energy dissipated by
the brakes
MCvdT/dt
Mass of brake
Specific heat capacity of brakes material
Temperature of brakes
How does the ABS work on an
aircraft?
If a wheel within the braking system is locking up,
the ABS releases that pressure momentarily so each
each wheel remains the same speed.
which aircraft systems use
electrical power as the energy
source?
Lighting
Navigation instruments
Fuel pumps
What types of circuits are used,
and what are their Voltage and
frequency levels
DC compatible circuits use 28V ( 0 frequency since
its DC)
AC can be variable or constant frequency. 115-200V
and ~400Hz
Name some aircraft electrical
power sources
Engines
APU
Ground network connections
Batteries
R.A.T (Ram Air Turbine)
How can we control frequency
in power generation?
Alternators convert variables into constant
frequency outputs
What does IDG stand for?
Integrated Drive Generator
What does CSD stand for?
Constant Speed Drive
What does VSCF stand for
Variable Speed Constant Frequency
What does VFG stand for
Variable Frequency Generator
How can we convert AC to DC
ATransformer Rectifying unit ( TRU) results in wave
rectification
How can we convert DC to AC
Uses a system comprised of an oscillator, phase
shifter, and transformer
How can we store electrical
power onboard
Batteries
Name some types of aircraft
batteries
Lead
Nickel-Cadmium
Silver-Zinc
Lithium-Ion
How can we prevent
electrostatic charges from
causing damage
Discharge rods dissipate static energy
What is the ‘‘Ram Air Turbine’’
In case of an emergency, the R.A.T is an external
energy generator, comprised of a turbine which is
moved by fast flowing air outside the fuselage.
Name all flight control surfaces
for pitch, yaw and roll
Elevators ( pitch )
Rudder (Yaw)
Ailerons ( Roll )
Name primary and secondary
flight controls
Primary - Roll, pitch and yaw based systems
Secondary - Flaps, spoilers, airbrakes, landing gear
retraction, reverse thrusters
What control surface
combination makes an Elevon
Elevator +Aileron
What control surface
combination makes a Flaperon
Flaps + Ailerons
What control surface
combination makes a Taileron
Aileron + Rudder
What control surface
combination makes a
Ruddevator?
Rudder + Elevator
Name all 4 methods for
actuating flight controls
Manual
Electric
Pneumatic
Hydraulic
Whats the purpose of a
balance tab on the control
surface
Provides aerodynamic balance and makes it easier
for the pilot to move the controls
Whats the difference between
power assisted and power
operated flight controls?
Power assisted allows for reversible controls
Power operated has no reversibility.
What are the main
characteristics of Fly-By-Wire
systems?
Replaces manual flight control with an electronic
interface
What are Fly by wire systems
advantages?
Reduced weight and pilot workload
Less chance of errors
What is the Fly-By-Wire weak
point?
The control software
Which types of aircraft cant fly
without Fly-By-wire
Unstable aircrafts - B-2 bomber
Forward swept wing aircrafts - SU-47
Thrust vector controlled aircraft - Sukohoi T-50
Manoeuvring difficulties aircraft - Harrier jet
Name all helicopter flight
controls and functions.
Collective pitch control/ Throttle - Changes AOA of
main rotor - Lateral movement
Cyclic pitch control - Horizontal directional control
Pedals- Yaw
Name 6 basic flight instruments
Airspeed indicator
Attitude indicator
Altimeter
Turn indicator
Heading indicator
Vertical speed indicator
What instrument tells about
pitch and bank angle?
The Attitude indicator
Whats the principle of pitotstatic instruments?
It compares static and ram( impact) pressures
How does the altimeter work?
Aneroid wafers expand and contract as
atmospheric pressure changes
How does the airspeed
indicator work?
Compares ram air from pitot tube with static air
from static port.
How do Angle of Attack
sensors work?
As the floating vane rotates due to airflow, its
position is transformed to an electrical output
Name some types of Angle of
attack sensors
Slotted probe
Floating vane sensor
Name some types of stall
sensors
Reed- type stall sensor
Switch type stall sensor
How does a stall sensor work?
As the angle of attack approaches its maximum, the
stall sensor warns so. It does this via vibrations and
sound.
Name any giro instrument
Attitude indicator
What instrument indicates your
turns
Turn and heading indicators
What types of heading
indicators are there?
Ring laser gyro
Fiber optic gyroscope
How does the magnetic
compass work?
Magnets mounted on the compass card align
themselves parallel to the Earth’s lines of magnetic
force.
What is the Glass cockpit?
An airplane cockpit that features electronic
instrument displays
What is autopilot?
A computer which can fly an airplane on its own.
Typically used to maintain flight rather than
land/take’off however these functions are possible
too.
How does radar work?
Radar is an electronic system that uses a pulse
transmission of radio energy to receive a reflected
signal from a target (echo).
What is GPS?
Global Positioning System. A system that determines
one’s exact location on Earth.
How does GPS work?
A GPS receiver determines a three-dimensional
position in space by calculating multiple ranges
from at least four satellites.
What is ILS?
Instrument Landing System. Assists in landing
What is reliability?
the consistency with which the same event is
repeatedly measured.
What is maintainability?
The probability a device which has failed will be
restored to operation within a given time
What is availability?
The proportion of system Up-Time over its lifetime.
What is the Mean Time To fail
(MTTF)?
Mean time until the first failure after entering
surface
what is mean time between
failures? (MTBF)
Measures the average time between failures of a
device
What is the mean time between
repair ( MTBR)
Mean time to restore the device to operating
condition
Name some types of
redundancy
Active redundancy and Standby Redundancy
What is the fuel system
purpose
To supply engines with fuel required for flight
What do we need to know to
size an aircraft fuel system
Required fuel volume
Limitations in shifting center of gravity
Min and max fuel flow rate
What % of MTOW is fuel for the
passenger aircraft
30-45%
Name some types of fuel tanks
Rigid reservoirs
Flexible reservoirs
Integral reservoirs
What is the purpose of a ‘tip’
tank, and where are they
located. What motion is most
affected by tip tanks?
Fuel tanks at the wing tips. Roll is affected most by
these.
What are advantages and
disadvantages of fuel tanks in
airplane wings?
Advantages- there’s lots of free space.
Easy to feed to the engines from here
Disadvantages - combat aircraft provides
dangerous challenges putting it there
Can also affect roll movement
How can we refuel an airplane
External fuel vehicles connect to the underside of
the wings
Air/vapor needs to be bled from the system prior to
refuelling
You can also fuel mid flight too
What do you do with excess
fuel during an emergency
landing
Dump it
What aircraft sub-system
handles fuel surplus?
Fuel jettison system
How can we measure fuel
levels in airplane tanks
Integration of the fuel flow to the engines gives a
rough idea..
Ultrasound or floating type with potentiometer
works well though
Describe how a fuel level
probe works
Ultrasound waves work by emitting high frequency
acoustic waves which are reflected and detected by
the sensor
What is the purpose of the
Environmental control system
It ensures the environment of the cabin/cockpit is
safe for passengers and comfortable too
What is the use of ECS on
board aircraft?
It manages cabin air pressure, air quality and cargo
ventilation/heating
What is ‘‘equivalent altitude’’ for
cabin pressure
Its the equivalent altitude pressure the cabin is kept
at ( ~ 8000ft )
What is the source of cabin air?
Air from the pneumatic system
Name one type of
thermodynamic cycle for
supply of cabin air
Bootstrap cycle
or
Refrigeration cycle
How can we control the
oxygen supply for passengers
in normal conditions
Increase air total pressure through the Air con
system
How can we control the
oxygen supply for passengers
in emergency conditions
Emergency oxygen masks and oxygen tanks drop
from above
