AVIATION – EVOLUTION FROM CONCEPTS TO REALITY.

HOW AIRPLANES FLY?

• Lift is the force that acts perpendicular to the relative motion of an object moving through a fluid, such as air. It’s primarily experienced in aviation, where it allows aircraft to overcome gravity and stay airborne.
• DRAG is the resistance offered by the air to the movement of the object through a fluid in this case which is air
• THRUST is the force that makes the plane move forward, thrust is generated by the engine of the airplane which propels it forward.
• WEIGHT is the mass of the plane that pulls it down because of gravity, the more the mass the greater the pull of gravity.

To fly the LIFT must be greater then WEIGHT and the THRUST far greater than DRAG. THIS EQUATION MUST BE RIGHT IN ORDER TO FLY.

EARLY CONCEPTS IN AVIATION

Leonardo da Vinci (1452–1519) was a Renaissance polymath known for his mastery in art, science, and engineering. His famous works include the “Mona Lisa” and “The Last Supper.” He designed innovative inventions like flying machines and armoured vehicles, showcasing his visionary thinking. Leonardo’s diverse talents and contributions continue to inspire creativity and innovation to this day.

LEONARDO’S CONTRIBUTION TO AVIATION

ORNITHOPTER

The ORNITHOPTER was a flying machine designed to imitate bird flight, conceptualized by Leonardo da Vinci. It failed to achieve sustained flight due to limitations in materials, power sources, and engineering technology of the time. The complexity of the flapping mechanism and the lack of suitable engines hindered its practical realization during Leonardo’s era.

HELICAL AIR SCREW

The helical air screw, designed by Leonardo da Vinci, was an early attempt at a helicopter-like device. Its principle involved a twisted screw-like blade rotating to generate lift and thrust. However, it failed due to limitations in materials, power sources, and engineering knowledge of the time. The lack of suitable engines, structural strength, and understanding of aerodynamics prevented its successful realization during Leonardo’s era.

PARACHUTE

Leonardo da Vinci designed a parachute concept around 1485. The parachute design consisted of a pyramid-shaped canopy made of linen cloth stretched over a wooden frame. The design was intended to slow down the descent of a person or object dropped from a height.

While Leonardo’s parachute design was innovative for its time, it was never tested during his lifetime. The concept lacked a means of deployment and a clear understanding of aerodynamics. As a result, it remained a theoretical design and did not lead to a functional parachute.

THE FATHER OF AERONAUTICS

Sir George Cayley (1773–1857) was an English engineer, inventor, and pioneer in aviation. He is often referred to as the “Father of Aeronautics” for his groundbreaking contributions to the science of flight. Cayley’s work laid the foundation for modern aeronautical engineering and established key principles that would shape the development of aviation.

• Concept of the Modern Aeroplane: Cayley conceptualized the modern aeroplane as a fixed-wing aircraft with separate systems for lift, propulsion, and control. He developed the idea of a streamlined fuselage, horizontal and vertical stabilizers, and a separate propulsion system, which became fundamental principles in aircraft design
• Aerodynamics: Cayley conducted pioneering research into aerodynamics, identifying the principles of lift, drag, and thrust. He studied the properties of air foil shapes and their effects on lift generation, laying the foundation for understanding how wings generate lift.
• Model Gliders: Cayley built and experimented with model gliders, using them to test different wing shapes, control mechanisms, and stability systems. His work with model gliders demonstrated the feasibility of heavier-than-air flight and the importance of aerodynamic stability.

THE WRIGHT BROTHERS

The Wright brothers, Orville (1871–1948) and Wilbur (1867–1912), were American aviation pioneers credited with inventing, building, and flying the world’s first successful powered airplane. Their historic achievement on December 17, 1903.

Design and Construction: Orville and Wilbur developed innovative design concepts for their aircraft, including a three-axis control system for pitch, roll, and yaw. They built their own lightweight 4-cylinder petrol engine and meticulously crafted the components of their aircraft for maximum efficiency.

First Powered Flight: On December 17, 1903, the Wright brothers achieved the first controlled, sustained, powered flight in history. Orville piloted the Flyer I, staying aloft for 12 seconds and covering a distance of 120 feet on its first flight. Later that day, Wilbur piloted a flight lasting 59 seconds and covering 852 feet.

FURTHER ADVANCEMENTS IN AVIATION

WORLD WAR-I

During World War I, propeller planes underwent significant development due to the urgent military demand for aerial reconnaissance, air combat, and bombing missions.

Engineers and designers experimented with various configurations to improve aircraft performance, manoeuvrability, and firepower.

Advancements in engine technology led to the introduction of more powerful and reliable engines, such as the rotary engine and the inline engine.

Aerodynamic improvements, including the use of air foils and streamlined designs, enhanced the speed and agility of propeller-driven aircraft.

The synchronization of machine guns with propeller blades, pioneered by Anthony Fokker with the Fokker Eindecker, allowed for more effective air-to-air combat.

Notable aircraft from this era include the Sopwith Camel, the Fokker Dr.I Triplane, and the SPAD S.XIII, among others.

World War I served as a catalyst for rapid innovation in aviation technology, laying the groundwork for subsequent developments in propeller plane design and production.

THE WORKING PRINCIPLE OF PROPELLER POWERED AIRPLANES

Propeller planes, also known as piston-engine aircraft, work on the principle of converting rotary motion into thrust. Here’s a basic overview of how they operate:

• Engine: Propeller planes are powered by piston engines. These engines burn aviation fuel (usually gasoline or avgas) in cylinders. As the fuel burns, it produces expanding gases that drive pistons up and down in the cylinders.
• Propeller: Connected to the engine is a propeller, which consists of two or more blades mounted on a hub. The rotating motion of the engine is transferred to the propeller.
• Thrust Generation: The propeller spins rapidly, creating a pressure difference between the front and back surfaces of its blades. This pressure difference generates thrust, pulling the aircraft forward.
• Lift and Flight: As the propeller generates forward thrust, the wings of the aircraft generate lift by creating a pressure difference between the upper and lower surfaces. This lift, combined with the thrust from the propeller, enables the aircraft to take off and maintain flight.

WORLD WAR-II

The evolution of aircraft during World War II saw rapid advancements in technology, resulting in the development of more capable and versatile planes. Here are some key aspects of this evolution:

• Engine Technology:
  • World War II witnessed significant advancements in aircraft engine technology. Radial engines, such as the Pratt & Whitney R-2800 Double Wasp and the Wright R-1820 Cyclone, powered many Allied aircraft, providing high power output and reliability.
  • The development of more powerful and efficient inline engines, like the Rolls-Royce Merlin and the Daimler-Benz DB 601, contributed to improved performance and speed in fighters and bombers.
• Aerodynamics:
  • Aircraft designs became more streamlined and aerodynamically efficient during World War II. Engineers focused on reducing drag and improving stability and control.
  • Advances in wing design, including the adoption of elliptical wings (as seen in the Supermarine Spitfire), helped enhance manoeuvrability and performance.
• Materials and Construction:
  • The use of lightweight yet durable materials such as aluminium alloys and stressed-skin construction became more widespread. This resulted in aircraft that were both strong and relatively lightweight, improving performance and range.
  • The introduction of new manufacturing techniques, such as spot welding and flush riveting, enabled more efficient production of aircraft in larger quantities.
• Armament and Avionics:
  • Aircraft were equipped with more sophisticated armament and avionics systems. Machine guns were supplemented or replaced by cannon armament, and technologies like radar and gyroscopic gun sights improved accuracy in combat.
  • The development of air-to-air rockets, guided bombs, and aerial torpedoes expanded the capabilities of aircraft in attacking ground and naval targets.

ERA OF JETS

Frank Whittle is often credited as the father of the jet engine. In 1930, at the age of 23, he patented the concept of a turbojet engine, which he had been developing as an RAF officer.

Whittle’s engine design featured a centrifugal compressor, combustion chamber, and turbine, and it operated on the principle of sucking in air, compressing it, mixing it with fuel, igniting the mixture, and then expelling it at high velocity to produce thrust. He faced numerous technical and financial challenges in developing his engine.

THE WORKING PRINCIPLE

Newtons third law states that every action has a equal and opposite reaction, jet engine works the same way,

The air is sucked in with and is left out at high velocity creating a trust which propels the plane. It is explained in three steps

• Air Intake and Compression:
  • The process begins with the intake of air. Air is drawn into the engine through the intake.
  • Once inside, the air passes through a series of compressor blades. These blades compress the air, increasing its pressure and reducing its volume.
  • The compressed air is then directed into the combustion chamber.
• Combustion:
  • In the combustion chamber, fuel is injected and mixed with the compressed air.
  • The mixture is ignited by a spark plug or other ignition source.
  • This ignition causes a rapid expansion of gases, creating a high-temperature, high-pressure exhaust stream.
• Exhaust and Thrust Generation:
  • The high-speed exhaust gases are expelled from the combustion chamber through a nozzle at the back of the engine.
  • As the gases are expelled at high velocity, they create a reactive force in the opposite direction according to Newton’s third law of motion (action and reaction are equal and opposite).
  • This reactive force is what propels the aircraft forward, generating thrust.
  • The cycle repeats continuously, with air continuously being drawn in, compressed, mixed with fuel, ignited, and expelled as exhaust, providing continuous thrust to the aircraft.

EVOLUTION OF JET ENGINE

• Early Turbojet Engines (1930s-1940s):
  • Frank Whittle and Hans von Ohain independently developed the turbojet engine concept. These early engines featured a centrifugal compressor, combustion chamber, and axial-flow turbine.
  • They were relatively simple compared to modern engines, with low compression ratios and limited power output. However, they demonstrated the feasibility of jet propulsion in aircraft.
• Axial-Flow Turbojets (1950s):
  • Advances in aerodynamics and materials led to the development of axial-flow turbojets, which featured multiple stages of axial compressors and turbines.
  • These engines offered higher compression ratios and improved efficiency, resulting in increased thrust and better performance.

• Turbofans (1960s):

• The introduction of turbofan engines revolutionized jet propulsion, especially in commercial aviation. Turbofans feature a large fan at the front of the engine that bypasses a significant portion of air around the core.
  • By increasing the bypass ratio (the ratio of air bypassing the core to that passing through it), turbofans improved fuel efficiency and reduced noise levels compared to pure turbojets.
• High-Bypass Turbofans (1970s-Present):

• High-bypass turbofan engines became the standard for modern commercial aircraft. These engines have very high bypass ratios, sometimes exceeding 10:1.
  • They are characterized by their efficiency, reliability, and quiet operation, making them ideal for long-range and passenger-carrying aircraft.

JET ENGINES IN MILITARY PLANES

1. Turbojet Engines:

• Turbojet engines were the first type of jet engines to power fighter aircraft.
  • They consist of a compressor, combustion chamber, turbine, and nozzle.
  • Turbojet engines operate by compressing incoming air, mixing it with fuel, igniting the mixture, and then expelling the hot exhaust gases through a nozzle to produce thrust.
  • Turbojet engines were predominant in early jet fighters such as the Me 262, Gloster Meteor, and F-86 Sabre.

• Turbofan Engines:

• Turbofan engines became more prevalent in modern fighter aircraft, offering improved fuel efficiency and lower noise levels compared to turbojets.
  • A large fan at the front that bypasses a significant portion of air around the engine core.They operate similarly to turbojets but have additional thrust generated by the fan airflow.
  • Many modern fighters, such as the F-15 Eagle, F-16 Fighting Falcon, and Eurofighter Typhoon, are powered by turbofan engines.

• Afterburning Turbofans:

• Afterburning turbofan engines, also known as “reheat” engines, are a variation of turbofans that feature an afterburner section behind the main engine.
  • Afterburners inject additional fuel into the exhaust stream downstream of the turbine, where it ignites and produces a significant increase in thrust.
  • This allows fighter aircraft to achieve supersonic speeds and enhances performance during combat manoeuvres.
  • Aircraft like the F-14 Tomcat, F-15 Eagle (in some variants), and MiG-29 Fulcrum utilize afterburning turbofan engines.

• Turbo-Prop Engines:

• Turbo-prop engines use a gas turbine to drive a propeller, combining features of jet and propeller propulsion.
  • While less common in modern high-performance fighter aircraft, turbo-prop engines are used in some specialized roles such as maritime patrol and ground attack.
  • Aircraft like the A-29 Super Tucano and the OV-10 Bronco utilize turbo-prop engines for close air support and reconnaissance missions.

• Ramjet and Scramjet Engines:

• Ramjet and scramjet engines are air-breathing engines that rely on high-speed airflow to compress incoming air without the need for a compressor.
  • While not commonly used in traditional fighter aircraft, experimental aircraft and hypersonic missiles may incorporate ramjet or scramjet propulsion for high-speed flight.
  • Examples include the X-51 Wave rider experimental aircraft and the BrahMos supersonic cruise missile.