Aeronautical Engineering Flashcards
First successful flight
1903 by the Wright brothers, made from wood and muslin, aluminum engine case
- lightweight, yet not able to withstand much flight
Ways to increase carbon efficiency in airplanes
Efficient jet fuel, additive manufacturing (e.g. 3D printing), more lightweight (fuel efficiency)
- have more passengers per flight (less individual flights)
- sustainable alternatives to fuels (biofuels, battery powered, hydrogen)
Henry Farman
added ailerons to control the ROLL
Developments during WW1
Material developments: first metal frame with canvas material on wings (red barons)
Between WW1 developments
Southern Cross: uses a plywood covering the skin on the wings (first aircraft to cross the Pacific)
Dornier Do X: highly inefficient and low range.
The Hindenburg distastor
Hydrogen-filled blimp, attempted to land, caught alight and exploded.
- exploration into different modes of transport
- used durallium: hard, lightweight (alloys begging to be used)
When were alloys beginning to be added
Around the 1930s
Range and endurance of aircrafts
How long it can travel, how long it can spend in the air
WW2 Plane developments and two planes (Mosquito, Spitfire)
Aircraft being designed for HIGH performance, combat: high altitudes and higher speeds
De Havilland’s Mosquito: bomber, the last wooden plane remaining
Supermarine’s Spitfire: Battle of Britain,
- wing designed with two ellipses joined together
- carburetor issues: when flipped upside down, fuel could not reach the engine. Solved by adding a ring.
Vampire: back stabiliser
(Boeing B-29) Superfortress:
- Heavy bomber, used in WW2 and the Korean war
- high altitudes, drops atomic bomb
End of WW2 developments:
Switch from carburetor engines to jet engines
Korean War Developments
North American F86 Sabre
- shape of wings: swept back wings (good maneuverability)
MIG-15:
- outmaneuvered Sabre (better pilot training and expereince)
- still used in North Korea
De Havilland Comet
1950s, commercial airline, issues with pressurisation in the cabin, windown and fuselabe
North American X-15
1960s, Supersonic plane
Supersonic issues
Noise pollution
Vietnam War Planes
General Dynamics F-111 Aardvark
- swept-back wings, wings closer up: generates more lift (can take-off in a shorter runway)
- stronger development in aerodynamics
Stalling in aircraft
As the angle of attack approaches over 16 degrees, this may not allow airflow to continue over the wing and flip it over
- not generating enough lift to counteract lift
Boeing 707
1960s, most significant commercial aircraft of its time.
- engine placed under wings
- larger take-off weight
- wider fuselag3
Boeing 747 (Jumbo Jet)
1960s, intially for military use
- carried 397 passangers (almost double the amount
- more economic
Saab AJ37 Thunderbolt
1970s:
- strange dual wing design: has ‘stol’ capabilities
- fast jet (could intercept other aircraft)
- PROBLEMS: did not have retractable wings, so couldn’t afford swept back winds
- increase of speed seen
Harrier Jump Jet
1970s, has vertical take-off capabilities (used on carrier ships)
- this can only be done at less then its maximum load weight, so is often used with a short take-off
- this is more used with landing.
Concorde
1970s:
- fatal incident, loud: noise pollution
- high attitude (difficulty landing, low visibility when landing)
Boeing 777
Modern
- extensive use of composites
Turbo-fan engines
- Twin jet
- wide-bodies
- aluminium and titanium for airframe
-
Advancements of electronics
Greater role in control of the airplane
- flight control computers, screens
- uses mechanisms e.g. actuators
- automation of flight
Airbus A380
Double Decker
- 61% made of aluminium alloys, 10% composites, etc
- first to use CFRP (carbon fibre reinforced plastics): lightweight (1.5 tonnes vs most aluminum alloys
-525 passengers: increase in passenger numbers
Boeing 787 Dreamliner
- dependent of composite materials
Carbon Fibre Reinforces Polymer (CFRP benefits)
lightweight, and so increased fuel efficiency
High Bypass engines
Wing shape
Reduces drag
Modern developments
materials (composite materials e.g. CFRP): reducing weight for fuel efficiency
More aerodynamic design: reduce drag
Modern winglets benefits
Reduces wingtip vortices (turbulence), greater fuel efficiency,
RAKED wingtips (give % increase to wing efficiency in Boeing 787)
Developments in wing materials
Fabric -Steel - alloys/composite materials
Titanium is used in US military, however is highly expensive
Improving aircraft safety
Autopilot: reduces human error, allows holding of altitude, and follows a set navigation plan.
Materials: stronger, lighter, more durable: less risk of failure
More ‘redundancies’/analogue backups: uses difference in pressure to calculate rate of climb, altitude, etc: allows this to be still measured in case of electrical failure
- precedence of backup battery
Glare
A combination of laminated Al alloy and glass fibre/expoxy (Airbus A380)
CFRP
Larger widows
Composite benefits
Do not corrode (less maintenance, longer lasting)
Light weight (increases fuel efficiency)
Advanced composite or Ti turbine blades
Reduced mass of engine, fuel efficiency, noise pollution
3D printing in airplanes
Quicker, less expensive process
- lighter
Chevrons
Parts on engines that reduce engine noise
LED impacts in planes
Longer lasting and reduces minimal heat: passenger comfort
Window technology advncements
Dimmable windows: gel layer that can be darkened by passing through voltage (Dreamliner)
2014: concept for windowless plane (lined with video display panels): reduces weight by reducing reinforcement structures
Electric systems in planes
used for brakes, drives for hydraulics (replace air-bleed systems)
- much easier to monitor for health, less maintenance
- reduced fuel rate
- lower life-cycle costs
Work health and Safety
Work Health and Safety act (2011): minimum standards
- monitor and improve work health and safety
Safety issues in aviation
Chemical hazards
- resins used in composites, paints, etc
Noise
- Jet engine: constant exposure leads to damage
Fibre dust
Fumes entering aircraft cabins
- e.g. carbon monoxide: can be monitored with a carbon patch
- VENTILATION is imporant
Societal impacts
Less travel time: used to take 6 weeks to sydney and london, now within 24 hours (more accessible, better postal)
- connect families and culture, tourism good for economy
Regional Australia: Royal Flying doctor service brings medical facilities
- regional areas gain quicker access to emergancy services, communication
Farmers use helicopters and light planes for monitoring land, herding and crop sprating
Aircraft used for geological surveying and cartographic services
Military purposes: drones, potentially autonomous
Environmental Impacts
Air pollution (piston and turbine engines with exhaust gases), fuel dumping (plane has to circle to burn fuel to reduce risks)
- more research into alternative fuels
Noise pollution:
- urban areas: has impact for people living in that area.
- curfews
- new turbine designs to reduce noise.
Aviation carbon costs
Only 2% of the total carbon emissions
Military impacts
Drones for medical supplies.
Aileron
Controls Roll, (z axis)
Rudder
Controls Yaw, at back of plane
Elevator
Controls the Pitch
Forces on an aircraft
- Weight v
- Lift ^ (upward for on wing to overcome weight)
- Drag < (air resistance)
- Thrust > (must overcome drag to increase speed)
Angle of attack
Controlled by pitch/elevator
Types of Airfoils
Early airfoils: significant undercamber, modern subsonic are more symmetric
Supersonic aircraft require different foil shapes
Venturi effect (Fluid dynamics)
Venturi effect: an incompressible fluid/s velocity must increase as it passes through a constriction (principle of mass cont.)
Bernoulli’s principle
increase of the speed of fluid occurs simultaneously with a decrease in static pressure.
Incorrect lift theory
- when air meats leading edge, airflow splits. This causes
- Newton’s 3d lay
- must be an equal force pushing foil upwards - Venturi theory
Correct lift theory
Flow turning
1. Speed is faster over top surface: lower pressure region on upper surface
2. Lower surface of the airfoil turns flow of air (but so does top surface: this is why planes can fly upside down.
Lift is related to
Drag types
Induced drag and parasitic drag
Induced drag
Pilot input The faster the plane, the lower the drag
Parasitic drag: graph shape and types
Increases exponentially as speed increases
3 types:
- form
- skin friction
- interference (e.g. wingtip vortexes)
Reducing drag
- Reducing frontal area
- Using smoother skin materials
- Adding winglets to disrupt vortices
- Reducing weight.
Laminar vs Turbulent Flow
Laminar: airflow is smooth, follows shape closely (streamlined). Kostly for small angles of attack
Lift-Drag ratio
Indication of aerodynamic efficiency
- higher ratio = more fuel efficient (powered) or with gliders, can fly long distances
When experiences no thrust (steadily descending): relates to angle of glide
- L/D = 1/tan(alpha)
Hydraulic systems
- operate undercarraige, flaps, and brake system.
Poarts:
- pump, regulator, reervoir, relief valve, filters, plumbing, oil, control valves, actuators, and an acccumulator
How is Hydraulic systems controlled
Moves control valve, directing hyrdraulic fluid to the actuator,
This pressure then moves the actuator, mechanically operating the service
control valve -> actuator
Air Pressure Types
Absolute Pressure: absolute vacumn
Atomospheric pressure: hydrostatic pressure caused by the weight of air: usually measured at sea level
Gauge Pressure: relative to atmospheric pressure. Positive for pressures above atmospheric, negative for pressures below.
Static pressure: Sum of gauge and atmospheric pressure
Dynamic pressure/velocity: additional pressure caused by movement of aur
Total: sum of dynamic and static
Flight instrument categories
- Pressure instruments
- Gyroscopic
- Compass
3 types of pressure instruments
- Airspeed indicator
- Altimeter
- Vertical Speed indicator
Pitot Tube and Airspeed indicator
Usually located below the wings, measures dynamic + static pressure.
Alternate Static Source
Side of the aircraft: away from airflow
Pitot Heater Switch
If too cold: becomes blocked by icing. Thus, the heater heats the pitot tube
Static Port
Allows in only the current atmospheric pressure
4 Stages of Combustion engine
- Intake: piston moves down, creating a vacuum to suck in air
- Compression: squeezes the air and makes it highly combustible
- Power: The spark plug ignites the mixture of gas, forcing the piston downwards
- Exhaust: exhaust gasses are released
Valves open and close the different chambers.
Early ice engines:
- Water-cooled, used in early aircraft
- Wright 6-70 inline 6 engine (1913)
Inline engines reached peak in WW1
The Curtiss B-8 V-8:
After 1908: water cooled
Rotary engines (what, pros and cons)
PROPELLOR engine
Have a large, usually odd number of cylinders: arranged around a crank case
- the whole engine rotates
PROS:
- more compact design, lighter, less machine parts
CONS:
- inefficient: requires more oil and lubrication (more moving parts)
-releases more emissions
- Lower thermal efficiency: doesn’t handle higher temperatures as well.
Radial Engines
Similar to rotary engines, however only the propellor rotates
- entered development even before Wright brothers
- liquid cooled: lighter then inline engines
- more reliable: run smoother
HOWEVER, large frontal area creates drag
- have to taxi in a S shape, as it reduces visibility
Planes using the Radial engine
Messerschmitt Me 163 Komet (up to 1130km/h)
Turbojet stages
- Intake: air enters inlet at high speed.
- Compression: Compressor blades force air into an increasingly narrow chamber
- Combustion: Air mixed with fuel and ignited
- Exhausted is vented out of the nozzle, providing thrust + spinning shaft.
How does a Jet Engine work
Mechanically simple system, generates high thrust by combustion, expelling an air-fuel mixture at high speeds.
Turbojet engines pros and cons
Fuel: inefficient, high noise pollution
BUT achieves high speeds
Afterburner
Additional fuel is sprayed into the jet pipe: ignites a second, fuel-inefficient burst of thrust
- achieve high thrust: military planes
Turbprop engines
High speeds achievable by turbojet engines: not good for passenger planes: used for regional, short-haul aircraft
- combines high power and low maintenance of a turbojet with the cruising speeds of a piston engine,
- done through gear reduction: between turbine shaft and propellor shaft
- quieter
Turbofan engines
Used for high altitude, long-haul flights
aka. bypass engines: produces 80% of the thrust.
Bypass air: high volume, low velocity = quieter, more efficient
CONS: size
Ramjet vs scramjet engines
Ram:
Air-breathing jet engine without rotary compression: do not work at low speeds, and often need a secondary propulsion system to achieve this speed. (doesn’t work above Mach 1)
- experimental military aircraft
Scramjet:
Above Mach 5 (used for missiles, etc.)
Rocket Propulsion
Exhaust fumes released by explosive chemicals are pushed out of the nozzle at high speed: generating thrust
- using them in space: need a chemical called and oxidant
- types of rocket propulsion
Solid:
Liquid:
- multiple steps allows for more control over turning it on/off: better performance
Applications of rockets
Military aircraft, missiles and satellite launches
German aircraft
Didn’t have mass manufacture capabilities: LESS planes
Comparison of Titanium. Aluminium and Magnesium
Density: Ti-> Al -> Mg
Ti: excellent creep resistance and strong + ductile, yet scare + expensive
Al and Mg alloys are more susceptible to creep at lower temperatures: not good for inside of crafts
v.s. Ti alloys and Steel
Alclad
A composite sheet, plate, etc. which a thin layer of almost pure Al. has been metallurgically bonded: hot-rolled into the surface.
- provided a corrosion resistant later.
Developed around late 1920s: used for skin on airframes.
Advantages of Alclad
High corrosion resistance
High fatigue resistance and strength
Relatively shiny finish
HOWEVER:
Heaver then unclad Al
Difficult to weld
Requires care when cleaning and polishing
Titanium Properties
moderate density
maintain mechanical properties up to 500 (can’t be used in induction part of the engine: more exhaust of fan.)
high strength
long fatigue life
good touchness
resistance to corrosion and oxidisation
Titanium uses in aero
airframes, langding gear and jet engines: good more military uses
Ti-6Al-4V
4x yield strength then steel
- Very high cost from titamium
Nickel Superalloys uses and properties
At least 50% nickel and up to 10 other elements (e.g. Cr, Al and Mb and Mb)
Used in jet turbine engines: turbine blandes and discs, furnace parts
- maitnain strength and creep resistance at high termpartautres
- long fatigue life.
BUT: high density so very heavy - its usage is minimised.
eg. Inconel
Creep
Plastic deformation process:
- load below the elastic limit for a long time, elevated temperature
- leads to permanent extension and failure
e.g. turbine blades: eventually extends them to hit the turbine casing.
Cobalt Alloys
Usually in the combustion stage of the engine (temperatures up to 1100)
- contains high level of Cr
Grain size impacts
Better properties occur with smaller grain size, however, creep resistance decreases: failure occurs at grain boundaries
- Thus: for turbines, advanced manufacturing techniques are developed to reduce grain boundaries.
Plywood in Aeornautial
In early aircraft fuselages, propellers and airframes
First introduction of composites (commercial)
1958: Boeing
- fibreglass skins used to cover aluminum honeycomb cores on secondary control surfaces (2% of external surface area)
- now: modern Boeing 787 dreamliners is 50% composites
Boron
Lightweight composite, mostly used for military applications
Boron fibres
boron fibres with a tungsten fore in a titanium matrix
Fibre metal laminates and types
Alternating layers of metals and composites
Good fatigue resistance
GLARE
ARALL
CARALL
Dreamliner construction
Constructed in several peices and places
Final assembly in Washington
WINGs and FUSELAGEL composite materials e.g. Torayca 3900-series CFRP prepreg tapes
Wing construction
Build box structure, supports large loads eperienced during flight: wings can be used for fuel storage
- Prepreg is laid onto a cure table
- Resin is cured in prepreg: baking it through heat or pressure
- Panel is trimmed to size
THEN ASSEMBLY:
1. automated drilling and fastening of upper and lower panels
2. Electrical systems and hydraulics are installed
3. Wing is shipped to Washington, control surfaces and wing tips then fitted.
primary vs secondary control system
control yaw pitch vs flaps, etc
Causes of corrosion in aircraft
Water, bad weather
- the environments: damn coastal areas, air pollution
- concentration cells in small crevices and between sheets of metal, fasteners
Dissimilar metal contact
Aviation fuel and exhaust gases
