1. Basic Aeronautics and Aerodynamics

2. Forces of Flight

3. Four Forces of Flight
4 fundamental forces act in an aircraft in flight
Forces have a magnitude and direction which makes them “vectors”
Vectors can be added and subtracted to give resultant or net force
When forces add to zero, aircraft is in steady flight
When a force is unbalanced, aircraft accelerates in direction of net force

4. All Forces Balance in Steady Flight

5. Forces in a Turn

6. LIFT

7. Showed that pressure of a fluid decreases as velocity increases
Daniel Bernoulli ( )
His work described the relationship between pressure and velocity in a fluid
Bernoulli did the pioneering work on fluid dynamics which forms the basis for aerodynamics
Showed that pressure of a fluid decreases as velocity increases

8. Airfoil Design

9. How an Airfoil Works
The shape of an airfoil generates lift when air flows over it
Relatively low pressure force downward
Higher speed flow (relatively low pressure)
Lower speed flow (relatively high pressure)
Relatively high pressure force upward

10. Wingtip Vortices

11. Vortices From Large Aircraft Are Very Dangerous

12. THRUST

13. Propellers

14. Propellers Convert Engine Revolutions to Thrust
Increasing speed
Notice the pitch decreases further away from the hub
This keeps the load even
The faster moving tip doesn’t need as much pitch as near the hub
A propeller is a spinning airfoil
Spinning propeller produces thrust
First successful aircraft propeller invented by the Wright Brothers

15. DRAG

16. Drag is Air Resistance to Motion
Flat plate
Sphere or Cylinder
Which has the most drag?
Which has the least drag
Airfoil

17. Laminar Flow Laminar flow is smooth
Turbulent flow has a lot of swirling and mixing
Laminar flow is desirable for aircraft as it has lower drag than turbulent flow
however there are other considerations we shall see later

18. Turbulence Notice how strings are not in straight lines
Turbulent flow results when airflow is no longer laminar and becomes “swirly”
Straight streamlines become unsteady and mix
BUT turbulence isn’t all bad……it “sticks” to a surface better than laminar flow

19. Highly Turbulent Becomes Separated Flow
Separated flow is highly turbulent flow that is no longer “attached” to the surface
Separated flow results in a HUGE increase in DRAG
In the case of an Airfoil it results in a STALL

20. Stalls Stall occurs when flow over wing separates
Separated flow results in high pressure
Result is loss of lift (and life if not corrected!)

21. Using Turbulence for Advantage
Turbulent flow remains “attached” better than laminar flow
Sometimes it’s better to have a turbulent flow than a laminar flow
For example, do you know why a golf ball has dimples??

22. Aircraft in Motion

23. Center of Gravity
The center of gravity is the average location of the weight of an object. In flight, both airplanes and rockets rotate about their centers of gravity.

24. Aircraft Move in 3 Axes

25. Longitudinal (Roll) Axis
Roll controlled by ailerons on the wings

26. Vertical (Yaw) Axis
Yaw controlled by the rudder on the vertical stabilizer

27. Lateral Axis
Pitch controlled by the elevator on the horizontal stabilizer

28. Flight Maneuvers Use all Three Axes

29. Aircraft Engines

30. Reciprocating Engines
Reciprocating engines are used in many aircraft
Same type of engine used in cars and trucks
Based on 4 stroke cycle also known as Otto cycle
1 power stroke for every 4 strokes
Nicolaus Otto
Germany

31. #1 Intake Stroke Valves Fuel/air mix
Intake valve opens and piston drops down and sucks in a mixture of air and fuel
Start

32. Valves close and piston moves upward compressing the fuel/air mixture
#2 Compression
Valves close and piston moves upward compressing the fuel/air mixture

33. #3 Ignition and Power Spark plug fires at top of compression stroke
Exploding gas pushes piston downward

34. Exhaust valve opens and piston pushes burned gases out of the cylinder
Hot exhaust gases
Exhaust valve opens and piston pushes burned gases out of the cylinder

35. Review
Can you follow the four stroke cycle??

36. Turbine Engines

37. Why Turbines?? Turbines (jets) are: Simpler (higher reliability)
Recip TBO 1500 to 2000 hrs
Jet TBO hrs
Smoother running
Produce much higher thrust at high speed
Capable of very high speeds (much higher than propeller engine)
Props loose efficiency at high speeds due to tip speed approaching Mach 1
Much higher power per unit weight (as much as almost 4:1)
But
Require special high temperature materials
High fuel consumption
Not efficient for low speed operations
Very loud (environmental issue)

38. A Quick Comparison Pratt & Whitney JT-9 Wright 3350 Characteristic
A Quick Comparison
Pratt & Whitney JT-9
Wright 3350
Characteristic
Lockheed 1049G
Boeing 747
Weight, W, lb
Speed, V, mph
330
530
Altitude, ft
23 000
35 000
Lift-drag ratio, L/D 15 16
Number of engines 4
Total cruise power, hp
6 585
59 934
Power per engine, hp
1 646
14 984
Dry engine weight, lb
3 675
8 600
Power to weight ratio
0.45
1.74

39. Turbojet Engines

40. Turbofan Engines
Turbofan has some of the good properties of a propeller engine such as better low speed efficiency but retains high speed jet performance

41. Turboprop Engines
Turboprop is more like a propeller engine with high low speed efficiency but lower top speed compared to pure jet

42. Ramjets and Scramjets
Instead of compressor turbines, ramjets use the “ram” pressure of inlet air for compression
Ramjets are very simple with no moving parts
But they can only operate at very high speeds

43. Structures and Other Systems

44. Fuselage Structure 3 main types of aircraft structures:
Truss
Monocoque
3 main types of aircraft structures:
Truss (used in early fabric covered airplanes)
Semi-monocoque
Loads carried by frame and skin
Monocoque
Loads carried by skin
Semi-monocoque

45. Landing Gear Conventional (“Tail dragger”) Tricycle Tandem
Fixed and Retractable - why is retractable gear a good thing??

46. Fuel Systems Fuel usually stored in wings Fuel “Feed” Gravity
Force (pumped)
Wing higher than engine
Fuel tanks in wings
Wing lower than engine