Which Aeronautical advancement was the most significant?

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Contents FOREWORD .................................................................................................................................. 3

INTRODUCTION ............................................................................................................................ 4

THE AGE OF GLIDERS .................................................................................................................... 5

The Works of Sir George Cayley 1773-1857 ................................................................................ 5

Otto Lilienthal-The Glider Man (1848-1896) ............................................................................... 6

Aeronautics came to the USA- Octave Chanute 1832-1910 .......................................................... 7

Summary.................................................................................................................................. 8

THE JET ENGINE REVOLUTION ....................................................................................................... 9

Engine Propulsion ..................................................................................................................... 9

Problems ................................................................................................................................ 10

Improvements and New Problems ........................................................................................... 11

Performance........................................................................................................................... 12

Summary................................................................................................................................ 14

MATERIALS................................................................................................................................. 15

Before the Jet Engine .............................................................................................................. 15

After the Jet Engine................................................................................................................. 16

High Temperature Materials.................................................................................................... 16

High Pressure Materials .......................................................................................................... 17

High Tensile Strength Materials ............................................................................................... 17

Summary................................................................................................................................ 18

CONCLUSION.............................................................................................................................. 19

BIBLIOGRAPHY ........................................................................................................................... 20

Internet sources ..................................................................................................................... 20

Books and Journals ....................................................................... Error! Bookmark not defined.

Audio-visuals .......................................................................................................................... 21

FOREWORD

Aeronautics, as I define it, means to move in the air, with Aero meaning ‘air’ and nautic

meaning ‘to move' or 'to navigate’. To be an aeronautical engineer is to be able to effectively design and mentor the manufacturing of machines which move in the air; such as an aeroplane.

However, does that mean building and flying a kite makes you an aeronautical engineer? Well

no, to be an accomplished engineer, the machines and systems you build must be for the forwarding of mankind and life on Earth.

Aeronautics is something which has interested me for many years. My interest in this subject

blossomed during a family holiday in 2011, sitting by the window seat in a Boeing 787; I observed how the wing shape changes during the various stages of flight. When I saw the flaps

of the wing extend down, increasing the wing area during takeoff, and the flaps come up during

landing, I was fascinated to say the least. This Extended Project Qualification (EPQ) allowed me to explore my interest in aerodynamics, and other aspects of aeronautical engineering too. I

have come to admire the complexity and creativity of engineering and respect how aeronautics benefits mankind.

The purpose of this EPQ is to present to you the journey of my first glimpse into the subject I

wish to study at University and hold as my profession. Visiting libraries to access different types

of books and accessing information on the internet, introduced me to the basics of aeronautical engineering. My EPQ also touches upon the historical aspect of aeronautics because of my own

separate passion for history, which I believe is naturally intertwined with a passion for science. It is very interesting to see how our technology and understanding of the forces and

mechanisms around us have advanced and strengthened through the years.

I decided to choose the question 'Which technical advancement in the history of Aeronautical

Engineering was the most significant and beneficial?' as my guide. I thought it was a question which would involve less reading and copying from books, and more thought and evaluation.

I hope you enjoy this brief project.

INTRODUCTION

Flying has always been seen as a miraculous spectacle. Even today, scientists still actually

ponder how a change in pressure across the wings, or some theoretical application of Newton’s laws, allows something to become airborne. It was this principle of flight, founded by the fathers

of aeronautics, which allowed the skies to become our highways. From the onset of the

pioneering age, key figures such as George Cayley, Otto Lilienthal and the Wright Brothers edged us closer and closer to finally fulfilling the dream etched into the minds of mankind,

sustainable flight.

The need to advance and ease human travel is what shapes the designs of our aeroplanes today and it is what drives our engineers to improve this exciting method of transportation. For

example, cargo planes should be made to have larger wings, a passenger plane should be built to

be more fuel efficient, and a fighter jet's structure should be designed to be more agile and to travel further on the same fuel. This essay is centred around the various improvements in

aeronautical history from the very first powered flight, which opened up the doorway to the pioneering age of discovery and luxury, to the most significant advancement of them all, the jet

engine, which separated the old from the new and the archaic from the modern.

The jet engine, could deliver so much thrust it required a rethink and redesign of every aspect of

the aeroplane. The aerodynamics of the aeroplane had to survive the higher speeds and altitudes which could not be achieved with an internal combustion engine. New materials were

needed to cope with the pressure changes and drop in temperature which came with flying at the altitudes which had not been reached before, but materials also needed to cope with the

higher temperatures of the powerful jet engines. It was this new powerful method of propulsion which began the exponential growth of aeronautical technology and allowed our global travel

market to be what it is today.

THE AGE OF GLIDERS

From the dawn of human intelligence, the idea of flying was etched into the minds of all those

yearning to take the sky and join the birds in their flight. The first attempts in taking the sky was a very primitive one; simple bird imitations would for some centuries be the ideal method of

conquering the sky and of course would always end in failure. However, it is wrong to think that

imitating birds is an absolute waste of time and effort when in fact much of our highly advanced aeroplanes today use mechanisms which evolve around the imitation of birds.

By the end of the 18th century, one man would change the concept of flight and aeronautics

forever. Inspired by Leonardo Da Vinci, George Cayley would come to change the pathway of aeronautics by inventing the modern airplane in 1799. Cayley’s experiments and designs would

come to inspire a chain of ambitious aeronautical engineers and flight enthusiasts, such as Otto

Lilienthal and Octave Chanute. Through their individual works they paved the way for one of mankind's greatest achievements of the 20th century; powered and controlled flight.

The Works of Sir George Cayley 1773-1857

Cayley completely abandoned the concept of “wing flapping” as his basis of flight; imitating

birds had been the main concept for centuries. Instead, Cayley envisaged that flight would only

be successful by separating lift and propulsion completely. He introduced horizontal and vertical stabilizers in the tail for flight stability and came up with the concept of fixed wings.

Cayley was also the first to state that lift was generated by low pressure on the upper surface of the wing. By this Cayley opened the door to modern aeronautical science and earned his title as

the "Father of aviation". 18

Fig 1.0 Cayley's invention of the first modern aeroplane in 1799 Source: Introduction to flight p1-35 (18)

Sir George Cayley's first design of the glider was also the first design of the modern aeroplane,

which would inspire generations that later culminated into the Wright Brothers success. Figure 1 shows the first model designed, built and flown by 1804; it was the first to have a fixed wing

and also had an adjustable tail.

However the aeroplane was too young of a technology and flight using balloons (First achieved

by Montgolfier in 1783)25 was much more experienced and suitable to the premature industry of the time.

George Cayley maintained his efforts to produce an airplane, and in 1849, he built and tested the first full size aeroplane, the infamous Boy Carrier.

Fig 1.1 George Cayley's Boy Carrier, Source: Introduction to flight p1-35 (18)

The “boy carrier "was a triplane; Cayley was the first to suggest this sort of idea of wings fixed

on top of each other mainly as a caution in case one wing broke. This concept perpetuated into the early 20th century and laid the foundation of aerostructures, such as bi-planes, in the late

19th and early 20th century.

This aircraft was made with:

A fixed wing at an angle of incidence for lift

An adjustable tail for horizontal and vertical stability

A pilot operated elevator and rudder

A fuselage in the form of a car

What was special about this model is the fact that it contained a pilot operated elevator and

rudder, the first of its kind and a technology which is still being used today. Nonetheless, flight was still very immature in the mind 19th century and Cayley was forced to revert back to using

flappers for propulsion, simply due to one glaring problem; a suitable engine was simply too heavy for effective lift. This problem, which encased the mind of every aeronautical engineer,

was finally solved in 1903 by the Wright Brothers.

Otto Lilienthal-The Glider Man (1848-1896)

Otto Lilienthal was the first human to sustainably fly before the invention of powered and

controlled flight in 1903, which respectfully earned him the title of 'Glider Man'. In 1891, Otto Lilienthal literally jumped into the air with his monoplane glider and flew in a fairly controlled

fashion.

Lilienthal was very much influenced by the works of Leonardo Da Vinci and George Cayley,

however his methods of research and investigating were unique compared to other early aeronautical engineers. He focused very precisely on the anatomy of bird wings as the basis of

the structure of his monoplane glider and combined that with the fixed wing idea proposed by Cayley. In 1889 Lilienthal published a book titled “Bird flight as the basis of aviation” 18.

Lilienthal would also come to have a philosophical impact on aeronautics for the next couple of

years since he believed that the best way to study flight was by getting up into the air and experimenting yourself.

“One can get a proper insight into the practice of flying only by actual flying experiments…The manner in which

we have to meet the irregularities of the wind, when soaring in the air, can only be learnt by being in the air

itself…”

Fig 1.3 Otto Lilienthal's Philosophy on aeronautical research, Source: Introduction to flight p1 -35 (18).

Lilienthal took his own advice and in 1894 and made the first successful non-powered flight

with his monoplane hang-glider.

Fig 1.4 Lilienthal’s flight attracted large audiences, Source: secret of flight (8)

Lilienthal’s No.11 glider was the most reliable one he built, made from willow branches and

English shirting material, this device made its first flight in 1894, flying hundreds of metres.

Lilienthal made over 2000 flights with his gliders and his inventions became imperative to the future of flight. The main concept learnt from Lilienthal was that flight could be maintained

without putting in any effort, contrasting previous ideas of looking at flight in a brute force manner. Lilienthal's work was quintessential to understanding flight stability.

Aeronautics comes to the USA- Octave Chanute 1832-1910

For the decades between the 1850's and 1890's, Britain and Europe where at the centre of the

early aeronautical advancements. In contrast, throughout this time the United States was busy consolidating its new government and expanding its frontiers. There was not much interest in

aeronautics at the time however, in 1875, a French-born US citizen named Octave Chanute intensively researched the works of previous pioneers' work on aeronautics and aviation, and

built his famous Biplane Hand Glider in 1896.

Of all the gliders built by Chanute, this Biplane was the most successful. Its outstanding feature

was the use of vertical struts and wire cross-bracing to make the wing structure,

which was the same cross bracing method used in railway bridges at the time.

Weighing only 14kg, this system combined

strength and lightness so effectively that it

was to become the standard for biplanes ever since and be the standard structure

for the Wright Brothers' airplane. Most importantly the biplane was so safe that

Chanute allowed journalists to fly it.

Fig 1.5 Chanute's biplane hand glider, , Source: Smithsonian National Air and Space Museum (9)

Summary

The advancements of pioneers of the late 19th century were small, but precious. Sir George

Cayley opened the door to modern aeronautics with his design of the fixed wing aeroplane. Otto

Lilienthal's wing design, inspired by birds, would also lay the foundations of monoplane wing design. Finally, Octave Chanute's cross-bracing would be the basis of wing design for biplanes; a

short-lived but a substantial era of aeronautics where aeroplanes would play a greater role.

Gliders broke us away from the idea of flapping like birds to fly and brought closer to controlled

and sustained flight. With the revolutionary flight in Kill Devil Hills in 1903, the beginning of the 20th century was full of an adventurous zeal for flying; the world witnessed the first insight into

a method of transportation which would revolutionize our travel, global connectivity and warfare.

However, the advancements which these pioneers contributed to aeronautics were not the most significant. Although their designs lay vital foundations of understanding, new challenges

emerged such as making flight safe, increasing flight ranges so that flight can be commercialized and making flight more sustainable. Their works unfortunately did not perpetuate through the

decades, but planted the seed for fixed wing aircraft. New evolutionary advancements in aerostructures replaced their designs.

THE JET ENGINE REVOLUTION

In the year 1903, the Wright brothers revolutionized aeronautics with the first engine

propelled flight. Aeroplanes could fly further, faster and higher. Likewise, in the mid 1940's another propulsion revolution occurred with the invention of the first practical jet engine,

which made high-speed flight possible with aeroplanes reaching speeds, altitudes and flight

distances that could not be achieved using piston engines. Jet engines also opened the world to safe, reliable and efficient travel. However, this revolution of propulsion would come to induce

another much needed upgrading of the material industry, since with greater altitude and speed comes a much greater performance requirement from the aircraft materials. Also, the

aerodynamics of aeroplanes had to be adapted to cope with these new speeds. This remaining chapter begins by firstly discussing the difference in engine performance

between the early piston engines and the jet engine. As engine performance came to be at the centre of aircraft modernization and overall enhancement, this is followed by how the jet engine

has affected aerodynamics and material performance.

Engine Propulsion

Propulsion before the invention of the jet engine was mainly produced from internal

combustion engines and propellers.

Propellers use aerodynamic force to generate thrust; a method widely used in the internal

combustion era due to inefficient engine performance. The illustration shows that these propellers have a cross section similar to aerofoil sections, however unlike wings; the aerofoils

are not in the same direction. The propeller is twisted so that at the root nearest to the hub, the chord line is parallel to the relative wind, while at the tip it is almost perpendicular. The shear

stress and pressure distribution over the propeller blade creates an aerodynamic force; however these forces act in different directions (vectors) due to the twisted blade. These two

forces are lift and drag, where the resultant is the net thrust.

Fig 3.0 Diagram of a standard propeller, Source: Introduction to flight p475 -449 (18)

The basic operation of internal combustion engines is a piston moving back and forth, which

powers a machine with a typical four stroke cycle as illustrated below18:

a) INTAKE STROKE: the intake valve is opened and the piston moves

down and the gasoline enters the cylinder. As the volume is increased,

its pressure stays the same since the valve is open.

b) COMPRESSION STROKE: The intake valve closes and the piston

compresses the gasoline liquid, increasing the pressure of the cylinder. At the end of this, the mixture is ignited usually by an electric spark,

drastically increasing the pressure while the volume is constant. The energy let off by the ignition leads to the next stroke.

c) POWER STROKE: The energy of the gasoline ignition forces the piston downwards, releasing the pressure and turning the crankshaft

which drives the propeller to produce thrust.

d) EXHAUST STROKE: As the piston is forced down, the pressure

decreases. Then the exhaust valve opens and the ignited gasoline is

forced out by the piston in another stroke. The pressure of the cylinder is returned to how it was during the intake stroke, and the

cycle begins again.

Fig 3.1 Series of diagrams on the sequence of piston engine strokes Source: Introduction to flight p449 -479 (18).

Problems

The main problem with both the propeller and the combustion engine was the efficiency of

their power output. The piston engine is on average 15% efficient. Energy is lost in many ways,

mainly through friction in the components and heat transfer. It is this low efficiency which means piston engine aircraft could fly no faster than 300 km/h. In addition to the hindrance in

speed, these factors affect the engines power output, which directly affects the power output of

propellers. Maintenance of Piston engine aircraft was also more intensive than Jet engines, with Piston engines requiring maintenance approximately every 2000 hours, due to more moving

parts13.

Jet engines were being developed in the mid 1940's by both British and German engineers

during the Second World War, with both countries vying to be the supremacy of the skies. The invention of the Jet engine by Frank Whittle and Hans van Ohain was an example of how war

can be a driving stimulus for scientific and technological breakthroughs. Nonetheless, the Jet engine was revolutionary due to its impact on the world of aircraft, military and civil.

The way the Jet engine produces thrust is an example of Newton's third law. However, another

way the jet engine produces thrust is similar to how propellers produce thrust. The result of the

high pressure in the engine forces the hot air out similar to the pressure described previously in the cylinder of a piston engine. The following paragraphs look at the Newtonian aspect of thrust

generation of jet engines, using Turbofan engines as the example since the power the majority of planes today.

Turbofans work similarly to Turbo Jets; air is sucked in, pressurized and rapidly depressurises

when it is blasted out through the nozzle at a much greater velocity than when it entered. The

force of the exhausted air against still air particles is what thrusts the aircraft forward, hence Newton's third law; however with Turbofans the engine is fitted with a powerful front-end fan,

which sucks in more air and creates a second stream to cool down the engine. The following is

the sequence of how turbofans produce thrust;

1. The large fan, which is a large diameter encased propeller at the front of the engine, accelerates a primary airflow through the various components of a typical turbofan engine. The

secondary airflow passes only through the fan and cools the engine; this airstream is also exhausted in the exhaust assembly.

2. The air passes through the low and high pressure compressors, which gradually increase the pressure of the air. The temperature in the compressor chambers can reach as high as 450oC.

3. The pressurised air then enters the combustion chamber, jet fuel is mixed with air and

ignited; the temperature reaches up to 1700oc.

4. The accumulated energy from the increase in pressure is converted in the stages of the

turbine chamber; the pressure of the air drops as it expands and passes through the turbines making them spin. This concentric spinning of the turbines within one another operate the fan

and the compressor fans. The Turbofan is therefore a flow cycle engine, since the turbines operate the fan and compressors.

5. Finally, the hot air is forced out of the exhaust assembly, which is narrowed to maximize the speed of the exhausted air, generating more thrust.

Source: CFM International 26

Fig 3.2 Diagram of a turbofan engine Source: Introduction to flight (18).

Improvements and New Problems

Due to the jet engine having fewer parts the flight hours before maintenance is approximately

3000 hours, which is much longer than the older internal combustion engines. So, although jet engines are more expensive to build, their maintenance costs are much lower. They are also

lighter compared to a piston engine which produces the same thrust12. The jet engine has made flight much more affordable and sustainable, which greatly expanded the air travel sector and

allowed businesses to invest more in global air travel. Jet engines are also far more efficient.

Efficiency is greater when the velocity of the exhausted air is closer to the velocity of the aircraft, which is why jet aircraft flying at greater altitudes are more efficient. At a greater

altitude, the atmosphere is thinner, so there is less drag. ;This means that less energy is required for an aircraft flying at a higher altitude than an aircraft flying at the same speed, but a lower

altitude, or, the same amount of energy will see an aircraft at higher altitude fly faster that an aircraft at a lower altitude.

More precisely;

Where c is the exhaust speed, v is the aircraft velocity and ηp is the efficiency. (Source: http://en.wikipedia.org/wiki/Propulsive_efficiency)13. More specifically:

Fig 3.3 Graph highlighting how an increase in Mach number of aircraft increases efficiency of engine. Source: Propulsive efficiency ( 13).

The Mach number is defined as the ratio of the speed of the object to the speed of sound. Bypass ratio is the ratio of the air sucked in by the fan into the second stream to that used in the combustion sequence. Therefore, as the speed/mach number increases, the efficiency of the engine increases.

Performance

Before the jet engine there was still a great deal of research being conducted in finding the

most effective aerofoil to increase the area of laminar flow and even today there is a great deal

of research and experimentation being conducted to achieve as close to 100% laminar flow on wings as possible. The maximum speed of aircraft steadily increased during the age of

propellers and piston engines; the maximum speed achieved in 1920 was 125 mph to nearly 450 mph during WW2. The highest maximum speed shown is for the P-51D aircraft which had a

speed of 437 miles per hour at 25,000 feet. Late in the war, a Republic P-47J achieved a speed in level flight of 507 miles per hour at 34,000 feet. The maximum speed is reliant on the engine

power, which also steadily increased in the pre-jet era16.

Before the jet engine was invented progress in creating more powerful engines was relatively

slow. Therefore, a great deal of research went into designing new aerofoils and aero structures which would reduce drag so that higher speeds were achieved with the same engine. .

However, with the design of the jet engine and with more thrust being generated, there was an urgent need to refine the wing design and body structure of aircraft to minimise the drag created by the fast moving wind. A new design was needed for the structure to survive these speeds and enhance performance.

Today a common design used for aeroplanes to endure these new speeds is with swept and

delta wings.

Nearly all modern high speed aircraft have swept and delta wings, but why? The benefit lies in how this design allows the aircraft to reach greater speeds. When the wings are swept back,

only a component of the oncoming airflow would contribute to the induced drag. There is an alternate explanation to why a swept wing increases the maximum speed; a swept wing will

decrease the thickness ratio of the wing thus reducing drag and allowing the Mach number to increase.

Fig 3.5 The French Dassault-Breguet Mirage 2000c is an excellent example of effective delta wings, Source: Introduction to flight p182-226 (18) Fig2.6 Vectors involved in swept wing design Source: Introduction to flight p182-226 (18)

After the invention of the jet engine, flaps on wings became much more common. An aeroplane usually experiences its slowest speeds during take-off and landing. The slowest speed in which an aircraft can fly at level flight is called the stalling speed. Stalling speed must be as small as possible for vital safety reasons, so that during take-off or landing (where stall speed is almost reached) the pilot would not lose control of the aeroplane. To decrease the stalling speed, the maximum coefficient of lift must be increased. Flaps are used to "artificially" enhance the lift properties of a wing; flaps increase the coefficient of lift as; 1. When using a flap the camber of the wing is increased; the more camber an aerofoil has at a given angle of attack, the higher the lift coefficient. 2. When the flap is deflected downwards it constitutes a chord line which causes an increase in the angle of attack.

Fig 3.7 Different designs and variations of flaps that artificially increase the coefficient of lift, Source: Introduction to flight p182-226 (18).

Summary

Before the Jet engine revolution a great range of aero structures did not exist; all

advancements in aerodynamics before WW2 were evolutionary and were only feeding off the slow evolution of internal combustion engines. However, even without the introduction of the jet engine the performance of aircraft was enhanced with the introduction of the modern aerofoil shape and moving away from the wing design of biplanes. The Jet engine however, had such a significant impact on aerodynamics, (due to the higher level of thrust produced which allowed aircraft to reach speeds never achieved before). Higher speeds meant that the aerodynamics of high speed aircraft had to be redesigned. The jet engine opened a gateway to various new wing designs and aero structures, such as swept forward/back wings, delta wings and winglet design, cementing its significance in the advancement of aeronautical engineering.

MATERIALS

The De Havilland DH 106 comet was the first jet powered commercial aircraft. However, a year

into service the aircraft suffered catastrophic metal fatigue in the airframes with three of its

aircraft breaking up in mid-flight completely ruining this aircrafts prospects in the commercial travel business. This is an example of how the aerospace industry of the 1950's was still

immature and was not ready to cope with fast high altitude flight made possible by jet engines. Nonetheless, the jet engine had a drastic effect on aerospace materials.

The demand for more advanced aerospace materials was introduced with the invention of the jet engine; the importance of structural integrity and material performance became integral to

aircraft advancements.. Although the performance of aerospace materials has changed, from the very first fabrics, to the advanced alloys and composites used today, one important aspect

regarding aerospace materials has remained the same; the need to use environmentally friendly and cost effective materials. As stated by the institute of physics in the introduction of their

book, “Aerospace materials”

“It is essential that the supply chain in the industry faces the prime drivers of cost (initial and life cycle), to-to-

market and platform performance. Aerospace materials and associated design and manufacturing processes

must be optimized in an integrated manner so as to deliver product competitiveness. The demands of

increasing environmental constraints enforced by local and worldwide legislations must also be addressed.

These challenges will only be met if the platform suppliers and material and semi-product manufacturers

collaborate effectively in strong partnerships to deliver the goals of minimum cost and maximum performance

in the required time-scales.”

Fig 3.8 Source: Institute of physics: Materials science and Engineering: Aerospace materials

Important definitions for understanding material properties are;

Specific strength: The specific strength is otherwise known as the strength-to-weight

ratio, the units are 𝜌

𝑘𝑔/𝑚3 .

Ultimate tensile strength: UTS is the ultimate stress a material can withstand before

breaking, where stress is defined as 𝐹

𝐴.

Yield strength: Yield strength is the stress point at which a material begins to plastically deform; plastic deformation being the point where a material deforms out of shape to

never return to its original form.

Ductility: Ductility is the materials ability to stretch while under a stretching force and return to its original form.

Malleability: Malleability is a materials ability to perform under a compressive force and return to its original position.

Before the Jet Engine

The first aerospace materials used where organic and from naturally occurring resources.

Although primitive compared to the materials used today, the materials selected had to be of the

highest quality. These included such materials as timber for wing structures

with fabric and dope to cover them; the timber would carefully selected14.

With the First World War the age of pioneering was ground to a halt and the aeroplane was quickly transformed into a war machine. With the new demand of fighter aircraft the British

National Physical Laboratory was responsible for "one of the first deliberately designed aerospace material"14. This material, the Y-alloy, was the first of a series of high strength, high

temperature HiDuminium alloys. The name HiDuminium is derived from high duty aluminium

alloys18.

Before the Jet engine advancement of material technology was used mainly in refining the manufacturing process with new evolutionary breakthroughs. The manufacturing process and

aircraft performance was steadily made more efficient with new composite materials and coatings being discovered.

A great deal of research also went into aircraft engine materials which benefitted from improvements in the car industry. The use of refractory alloys with very high melting points

made aircraft engines much more reliable, increasing the range of flight.

After the Jet Engine

The advancement of alloys and other materials was intertwined with the advancement of

aeroplane engines. For instance, with the invention of turbine engines by Frank Whittle and Van

Ohain, there was a demand for high-temperature materials which would survive inside combustion chambers and the nozzle. Similarly, with new speeds being achieved by aeroplanes

pressure resistant materials were now in high demand.

Historically, the advancements in materials technology have been evolutionary. However, with

the Jet engine revolution under-way, new revolutionary materials were required to maintain the performance of jet aircraft. Composites were the fundamental basis of these new

revolutionary materials; they are materials made from a combination of elements whether it be different metals making up an alloy or different orientations of carbon fibre or glass fibre, to

combine and improve the properties of the individual elements

Even now there is a high demand for stronger, tougher, but lighter materials as commercial aeroplanes continue to become bigger to maintain the booming global air travel market. This is important as we don't want aircraft to become heavier with increased toughness, since this would result in greater fuel consumption.

High Temperature Materials

Increasing the temperature of the atmosphere a material is in has many effects; it reduces the

strength, increases the rate of corrosion and oxidisation of materials. High temperature

materials are at the core of material engineering. It is the science of maintaining material

properties to as high of a temperature as possible.

Carbon Composites are used extensively in modern aircraft due to their high specific strength. The ability to withstand high temperatures without increasing in size makes it an effective high

temperature material. However, carbon composites, in their natural form, are susceptible to significant oxidisation (rusting) at temperatures above 500℃. To address this problem a layer

of Silicon raises the limit to approximately 2200℃.

Ceramic is another example of a good high temperature material; used extensively in the nose

caps of space shuttles to withstand soaring temperatures of atmospheric re-entry. They are also used as coating layers for turbine blades20.

High Pressure Materials

As previously mentioned, carbon fibres have useful high temperature properties. Although

being expensive, their excellent strength-to-weight ratio makes them the ideal material for

aeroplane structures20.

fig. 3.9 Carbon fibre wings used in the A350 XWB. Source: Airbus Official Website.

High Tensile Strength Materials

Hybrid composites are materials which are constituted with three materials, with at least one

of them being a metal. These Hybrid composites, otherwise known as Metal Matrix Composites

(MMC) are more advanced compared to most composites.

Titanium-Aluminium Alloys are an example of MMC; they have very high tensile strength and

they can withstand oxidisation to temperatures up to 1600℃. They also have a very high melting point making them ideal for use in landing gear systems, as they are able to withstand

shock and impact and the high frictional temperature20.

Fig 3.91 The Landing gear of a Boeing 777-300 Source: Wikipedia: Landing gear (11).

Summary

Material advances can be linked back to how the jet engine was at the core of the

revolutionary aeroplane redesign. Materials were gradually improving before the 1940’s, with advancements in melting points and tensile strength. But, with the catastrophe of the De

Havilland in 1954 it was made clear that new, advanced materials were required for use on aeroplanes. The jet engine's impact on flight required revolutionary materials designed to

handle the higher altitudes, greater changes in pressure, new extreme temperatures (hot and cold), increased forces and stresses; it was composite materials which would be at the core of

modern aircraft design.

CONCLUSION

Both the first powered flight in 1903 and the invention of the jet engine were revolutionary

advancements. However, in my opinion, the invention of the Jet engine was more significant for

many reasons; their impact on propulsion allowed aeroplanes to fly much faster, travel longer distances and to provide thrust far more efficiently. Standard aerodynamic designs of

aeroplanes had to be entirely rethought in order for the aeroplane to survive these speeds, and new materials had to be invented to withstand the soaring pressures and temperatures of jet

flight. Not only that, but the jet aircraft has allowed flight to become commercialized, due to the efficiency of this new technology; as a consequence our world is more interlinked than ever

before, and flying is now regarded as a common form of transportation within our global

society.

From what I learnt from my research, by the end of the 18th century, the mind-set of the first aeronautical engineers was a more adventurous one. Even after 1903, flying was regarded as an

adventure and a luxury. The pioneering age following 1903 involved a great deal of racing and bizarre records, such as playing tennis on a flying aeroplane. This comes to show that the

technology of flight was still not taken very seriously; it was regarded as a luxury and only small

advancements took place with nothing strikingly advancing the technology of flight. The only major leap before the jet engine was leaving the biplane wing design introduced by Octave

Chanute. The last Biplane to be mass produced was the Italian Fiat CR.42 Falco in May 193824.The evolution from biplane to monoplane wing design was also a product of war

demand, with the Spanish civil war underway and the Second World War at hand, European nations and the USA were racing to evolve their aircraft and were vying for supremacy of the

skies.

In the intense aerial combat of the Second World War there was a huge demand for new cutting

edge aeroplanes, with the Messerschmitt and the spitfire as prime examples of how war can be the most pressing demand for aeronautical engineers. Unsurprisingly, the jet engine was

invented in the heat of the Second World War. This revolutionary invention, which mixed efficiency and power so well, would change flight forever.

Today our global air travel market is one of the most technologically advanced of them all with amazing new aeroplanes such as the A380 and the Boeing 787 being invented. We are entering

an age of exponential growth and advancement, however with new breakthroughs come new challenges. In our age, fuel efficiency, noise reduction, reduced maintenance and building costs,

increased safety and efficient propulsion are at the core of our thinking. Is the next revolutionary invention- an eco-friendly, economical, super-efficient, sustainable, but powerful

propulsion system? With our depleting natural resources, it looks like it must be.

BIBLIOGRAPHY

Internet sources

1.Wikipedia (updated 2014) Propulsive efficiency-Mechanical Efficiency, http://en.wikipedia.org/wiki/Propulsive_efficiency

2. Wikipedia (Updated 2014) Aerospace materials-History, http://en.wikipedia.org/wiki/Aerospace_materials 3. Britannica Encyclopaedia website (2014), Leonardo Da Vinci Gallery,

http://www.britannica.com/EBchecked/media/95182/Leonardo-da-Vincis-plans-for-an-ornithopter-a-flying-machine 4. History of Airships and Balloons, First Flight and the Montgolfier brothers,

http://inventors.about.com/od/astartinventions/ss/airship_2.htm 5. Hargrave: The Pioneers, Aviation and Aeromodelling Interdependent Evolutions and Histories, http://inventors.about.com/od/astartinventions/ss/airship_2.htm

6. Aerospaceweb.org, Origins of Control Surfaces, http://www.aerospaceweb.org/question/history/q0103.shtml

7. Elsecretodelospajaros, El-Boy Carriers, https://elsecretodelospajaros.wordpress.com/2013/03/09/el-boy-carrier/

8. The Secret of Flight, Understanding why it is possible to fly, http://secretofflight.wordpress.com/gliders-2/ 9. Smithsonian National Air and Space Museum, The Breakthrough Concept,

http://airandspace.si.edu/exhibitions/wright-brothers/online/fly/1899/breakthrough.cfm 10. Aviastar, Langley Aerodrome, http://www.aviastar.org/air/usa/langley_aerodrome.php

11. Wikipedia Official Website, Landing Gear, http://en.wikipedia.org/wiki/Landing_gear 12. Shoreline Aviation( 2011) , Piston engine aircraft vs. Turboprop engine aircraft, http://www.shorelineaviation.net/news---events/bid/50442/Piston-Engine-Aircraft-vs-

Turboprop-Engine-Aircraft 13. Official Wikipedia Website, Propulsive efficiency, http://en.wikipedia.org/wiki/Propulsive_efficiency

14. Official Wikipedia website, Aerospace materials, http://en.wikipedia.org/wiki/Aerospace_materials

Books and Journals

15. Yoseph Bar-Cohen (2014) HT materials, CRC PRESS: High Temperature Materials and

Mechanisms, p.5-7

16. Laurence K. Loftin Jr. (1985) The age of propellers, Quest for performance: The Evolution of modern aircraft, p. 103-110, 152-153

17. Rowland White (2013), The first Bird Imitations, In. Bobby Birchall (des.) TRANSWORLD PUBLISHERS The Big book of flight, p. 8-15.

18. John D. Anderson (2011), Chapter 1: The First Aeronautical engineers, Chapter 5: Aerofoils, wings and other aerodynamics shapes, Chapter 9: Propulsion. In. Anne T. Brown, Lyn Beamesderfer and Scott Amerman (eds.) Mc Graw Hill Introduction to flight , p. 1-35, 182-226,

475-499. Eric Brown (2007), 19. It is utter nonsense to believe flying machines will ever work, In. Amber Tokeley, and

Sarah Sherlock (eds.)DK: The colour encyclopaedia of incredible aeroplanes, P. 6-8 Airbus Official Website, A350 XWB, http://www.a350xwb.com/advanced/wing/#first-in-

composite-wing.

20. Types of Super Alloys (2013), Ed. Sam Zhang, Dongliang Zhao, Aerospace Materials

Handbook.

21. Chapter 7 Materials Developments in Aeroengine gas turbines (2001), Ed. David Clark,

Steve Bold, Aerospace materials

22. History of the Airbreathing Jet engine (2014), Saeed Farokhi, Aircraft Propulsion

23. History of Engines (2008), Saeed Farokhi, Aircraft propulsion and gas turbine engines

24. Early Fighters (2000), Christopher Chant, ISLAND BOOKS, The world's greatest aircraft, p

12-62

25. Richard Holmes (2013), KNOPF DOUBLEDAY, Falling upwards: How we took the air

Audio-visuals

26.CFM International, How does a turbofan CFM567 engine work, https://www.youtube.com/watch?v=_LaKlE2h3Jw 27. Mohammad Tawfik (2014), Airfoils and Wings: Thickness Ratio,

https://www.youtube.com/watch?v=qgJBIZABWeM