Principles of Flight: Wright Brothers & Aerodynamics

• Aerodynamics and Flight Characteristics is module 644-1
• Lectures are on Mondays and Thursdays, 4. DS (01:00 - 02:30) in room POT 051
• Exercises are on Mondays and are embedded within the lectures
• The written exam is 180 minutes and the use of calculators is permitted if they are not PDA or handheld
• Contact [email protected] for further inquiries
• Consultation time is Wednesdays, 9:20 – 10:50
• Course details: https://tu-dresden.de/bu/verkehr/ila/ifl/studium/lehrveranstaltungen/aerodynamik
• Registration and scripts available via OPAL

Definitions

• Flight mechanics describes the behavior of bodies moving in the atmosphere using aerodynamics.
• Aerodynamics is the part of fluid dynamics describing bodies' behavior in compressible fluids like gases.
• Flight controls are systems controlling aircraft around three spatial axes.
• Aeroelasticity is the umbrella term for physical processes on structures where aerodynamic loads interact with elastic structures (not a focus of this course).

Course Overview

• Introduction
• General aerodynamics
• Aerodynamics - Aerofoil
• Flight mechanics - Basics
• Controls
• Stability

Introduction: Historical Overview

• Around 1500, Leonardo da Vinci created "engineering" designs for flying machines.
• Around 1670, Francesco Lana di Terzi suggested airships using the "lighter than air" principle.
• Francesco Lana de Terzi (1631-1687, Lombardy) was an Italian Jesuit priest, mathematician, naturalist, and aeronautics pioneer and Professor of physics and mathematics at Brescia
• He developed the first sketched concept for a vacuum airship and has been referred to as the Father of Aeronautics having written the book "A theory of aerial navigation verified by mathematical accuracy"
• In 1709, Bartolomeu de Gusmao made the first model of a hot air balloon, with a paper balloon rising 4 meters before the King of Portugal.
• On 21.11.1783, the first ascent of a Montgolfier hot-air balloon in Paris occurred with two people onboard
• On 07.01.1785, the first crossing of the English Channel happened in a hot-air balloon, however a problem existed for the the lack of direction control.
• Sir George Cayley developed aerodynamic flight and made a glider model of 1.6 meters in 1804 and completed the first unmanned flight in 1809
• In 1809/1810, Cayley published his findings from experiments under the title "Aerial Navigation" in Nicholson's Journal stating, "The whole problem of flight is within the following limits: 1. A surface must be made load-bearing for a given weight by applying a force against the resistance of the air. 2. The pitched wing - equipped with a propulsion mechanism - that is the true principle of aviation."
• In 1889, Otto Lilienthal published "Bird flight as the basis of the art of flying" by carrying out systematic gliding flight investigations, compiling data on the aerodynamic shape of wings, and elaborating on lift and drag development
• Otto determined that curved wings are better suited than flat wings for "lifting power"
• In first gliding experiments: wingspan was 6 to 10 m, wing area of approx. 14 m², standing exercises against the wind and jumps from the springboard in his garden
• On 9 August 1896, Lilienthal crashed from about 15 meters due to a "solar gust" (a thermal detachment)
• The Wright Brothers created the first functioning triaxial control system (Dreiachssteuerung):
  • Rudder (Seitenruder) to control yaw movement.
  • Elevator (Höhenruder) to control the angle of attack and longitudinal flight path (climb or descent).
  • Lateral control (Quersteuerung) via wing twisting (roll motion).
• The Wright Brothers powered maiden flight was on 17.12.1903 for 260m at 16km/h
• 5.10.1905 Flyer 3 already flew for 39 minutes
• In October 1900, the Wright brothers tested gliding with a biplane glider
• In the summer of 1901 they accomplished manned gliding flights up to 100 m using up to 35 km/h headwind with the pilot operating the apparatus lying down with poor stability with regard to the aileron and yaw axix
• Theoretical approaches to flight came about as insights were not gained from theoretical predictions and therefore practical verifications were needed for the transferal of natural principles, such as bird flight
• From approx. 1890 (Lilienthal), the goal was to Develop a theoretical foundation for lift, controllability and stability
• There was an example of aerofoil Joukowski transformation
• In 1909, the First lectureship in aviation occurred when Ludwig Prandtl taught in Göttingen
• Aircraft test tracks of the DVL in 1915 carried out preliminary tests with models in the Göttingen wind tunnel where as in 1916, Tower car with DVL Berlin-Adlershof aircraft were measured for air resistance.
• The Messerschmitt Bf 109 (Me 109) was in the Braunschweig wind tunnel during 1939 and achieved 755 km/h and 1800 PS
• In 1989, the Grumman F9F-2 Bearcat was tested, reaching 850 km/h and 4000+ PS
• Hugo Junkers did industrial research with fundamental considerations on design and material properties,
• He investigated the construction of efficient and profitable transport aircraft with the idea coming about for wing- only aircraft (thick, cantilever (freitragender) wing)
• In 1910, Junkers patents a physical design of the wings
• The thick wings can accommodate tanks, engines or cargo
• The 1915 Development of the first was the all-metal aircraft J1: powered by 88 kW (120 PS) which achieved 170 km/h and a take-off mass of 1080 kg with a length of 8.6 meters and a wingspan 13 meters and a maden flight occurign on 12.12.1915

Wing

• National Advisory Comitee for Aeronautics was a state organisation, the predecessor for NASA performing Basic research in aviation
• There is a conflict between drag (thickness of the airfoil, angle of attack), lift (curvature of the airfoil) and aeroelasticity (stability) of the airfoil

Classification of aircraft - Lift

• Aircraft with static lift - Lighter than air:
  • FLStat = (Pair – Pgas) * V * g
  • Pair...air density [kg/m³], V...Volume [m³], g... gravitational constant= 9.81m/s²
  • Hydrostatic pressure depends on the height of the location p=p g h
  • aerostatic Buoyancy = weight force of the deformation of the fluid (liquid, gas)
• On a body immersed in fluid with density rho, buoyancy force
  • F₁=ρgV
  • V...the volume displaced by the body,
  • ρν...the mass of the fluid displaced by the body
  • pg V...its weight force
• As soon as the weight force of the body is smaller than the lift force, the body rises
• Shape of the body does not matter (hydrostatic paradox)
• Quantity of surrounding fluid does not matter, but there must be fluid bellow the body (Archimedes' principle
• Aircraft with dynamic lift:
• FL,dyn = CL * ρ/2 * v² * Awing
  • An airfoil is a streamlined shape that can generate significantly more lift than drag vs a flat plate which can generate lift, however has somewhat higher drag
  • The flow over the upper surface is faster than the flow over the lower surface
  • The curved upper surface acts as an obstacle forcing streamlines to pinch closer, making streamtubes narrower
  • If streamtubes become narrower, conservation of mass requires that flow speed must increase
  • Reduced upper-surface pressure and upward lift follow from Bernoulli's principle
• Bernoulli's principle:
  • An increase in the speed of a fluid occurs simultaneously with a decrease in static pressure and also a decrease in the fluid's potential energy
  • Can be derived from the principle of conservation of energy where, in a steady flow, the sum of all forms of energy in a fluid is the same at all points
  • This requires that the sum of kinetic energy, potential energy and internal energy remains constant
  • -> an increase in the speed of the fluid occurs with a simultaneous decrease in the sum of potential energy including static pressure and internal energy

Aircraft

• Can be classified by:
  • If it employs aerostatic lift i.e. Airships, Free Balloons and Captive Balloons
  • If it employs aerodynamic lift i.e. Powered Helicopters, Gyrocopters or Non-Powered Gliders
  • By how it generates lift i.e. Rotorcraft such as Helicopters and Gyrocopters or Fixed-wing aircraft

Definition - Aerodynamics:

• Is the study of physical laws applying to the flowing, compressible gases and bodies around it and also encompasses air resistance and lift
• Considers the laws of flow, magnitude, direction, point of application and dependence on influencing variables
• Invesitgates forces and moments acting on the body, derives Laws and calculates the magnitudes and directions as a function of influencing variables to generate "lift and thrust" and and overcome "wieght force" and "resistance to movment
• Dependent on physical properties of air:
  • Dependance on pressure, density, temperature, compressibility and vicosity
  • Geometric shape of the aircraft components
  • Shape of the airflow
  • Speed, angle of attack and angle of sideslip

Definition – Flight mechanics

• It describes the movements of aircraft in the air during flight, and on the ground during taxiing
• Investigates conditions under considering laws of motion where the aim is to present fundamental relationships of movement
• Presentation of fundamental relationships of the movement of aircraft in two groups: -Flight performance in terms of efficiency such as horizontal speed, service ceiling, and angle of climb, -Flight characteristics (operational behavior), a measure of safety (e.g. stability, stall behavior)

Explore the Wright brothers' flight control system and aerodynamics. Understand key concepts of flight mechanics and the differences between aerodynamics and fluid dynamics. Learn about aeroelasticity and the development of early aircraft.