Theory of Flight Part 1 PDF

Theory of Flight 8.3 - Theory of Flight 1 Introduction 8.3 - Theory of Flight 2 Four Forces of Flight 8.3 - Theory of Flight 3 Vectors 8.3 - Theory of Flight 4 Lift 8.3 - Theory of Flight 5 Weight 8.3 - Theory...

Theory of Flight 8.3 - Theory of Flight 1 Introduction 8.3 - Theory of Flight 2 Four Forces of Flight 8.3 - Theory of Flight 3 Vectors 8.3 - Theory of Flight 4 Lift 8.3 - Theory of Flight 5 Weight 8.3 - Theory of Flight 6 Centre of Gravity 8.3 - Theory of Flight 7 Centre of Gravity 8.3 - Theory of Flight 8 Center of Gravity 8.3 - Theory of Flight 9 Center of Gravity 8.3 - Theory of Flight 10 Adverse forward Center of Gravity 8.3 - Theory of Flight 11 Adverse rear Center of Gravity 8.3 - Theory of Flight 12 Effect of Stall Speed on Centre of Gravity 8.3 - Theory of Flight 13 Imbalanced Centre of Gravity 8.3 - Theory of Flight 14 Effect of forward Centre of Gravity on Aircraft Performance and Stability 8.3 - Theory of Flight 15 Effect of Aft Centre of Gravity on Aircraft Performance and Stability 8.3 - Theory of Flight 16 Lifting Forces 8.3 - Theory of Flight 17 Lifting Forces 8.3 - Theory of Flight 18 Lifting Forces 8.3 - Theory of Flight 19 Lifting Forces 8.3 - Theory of Flight 20 Center of Gravity Limits 8.3 - Theory of Flight 21 Straight and Level Flight 8.3 - Theory of Flight 22 Forces in a climb 8.3 - Theory of Flight 23 Forces in a descent 8.3 - Theory of Flight 24 The Glide 8.3 - Theory of Flight 25 Glide Angle 8.3 - Theory of Flight 26 Aircraft Glide 8.3 - Theory of Flight 27 Aircraft Glide Ratio This explains why minimizing drag is so critically important. Because drag varies with airspeed, the glide ratio must also vary with airspeed. A glide polar shown in the Figure 3–15 is a graph, normally provided in a glider’s flight manual, that details the glider’s still air sink rate at airspeeds within its flight envelope. The glide ratio at a particular airspeed can be estimated from the glide polar using: 8.3 - Theory of Flight 28 Aircraft Glide Ratio Airspeed and sink rate must both be in the same units. The minimum sink speed is the airspeed at which the glider loses altitude at the lowest rate. It can be determined from the polar by locating the point on the graph with the lowest sink rate and reading off the corresponding airspeed. 8.3 - Theory of Flight 29 Aircraft Glide Ratio The best glide speed is the airspeed at which, in still air, the glider achieves its best glide ratio. It is also known as the best lift/drag (L/D) speed. This can be determined from the polar by drawing a line from the origin that is tangential to the curve (e.g., just touching). The point of contact is the best glide speed; the glide ratio at this speed can be calculated as previously described. In still air, the glider should be flown at this speed to get from A to B with minimum height loss. 8.3 - Theory of Flight 30 Aircraft Glide Ratio Increasing the mass of a glider by adding water ballast, for example, shifts the glide polar down and to the right. The minimum sink rate is therefore increased, so as expected, the extra weight makes it harder to climb in thermals. However, the best glide ratio remains approximately the same, but now occurs at a higher airspeed. Therefore, if the thermals are strong enough to compensate for the poor climb performance, then water ballast allows a faster inter-thermal cruise. This results in greater distances being traveled per time interval. 8.3 - Theory of Flight 31 Glider Fly 8.3 - Theory of Flight 32 Gliding Flight Power-off glide (T=0) Power-off Flight path angle (Glide angle) Airplane in power-off gliding flight (No thrust) Equations of motion for power-off glide Forces parallel to the flight path (6.54) Forces perpendicular to the flight path (6.55)  (6.54) (6.55) Eq. (6.54) / Eq. (6.55) Therefore (6.56) The higher the L/D, the shallower the glide angle (θ) Example The maximum L/D for the CP-1 is 13.6. Calculate the minimum glide angle and the maximum range measured along the ground covered by the CP-1 in a power- off glide that starts at an altitude of 10,000 ft. Solution (6.56) As shown in Figure on the right (6.56) Example 2 Repeat Example 1 for the CJ-1, for which the value of (L/D)max is 16.9 Solution 2 (6.56) Centrifugal Force 8.3 - Theory of Flight 40 Centripetal Force 8.3 - Theory of Flight 41 Aircraft Turn 8.3 - Theory of Flight 42 Turning Flight 8.3 - Theory of Flight 43 Turning Flight 8.3 - Theory of Flight 44 Sideslip 8.3 - Theory of Flight 45 Skidding 8.3 - Theory of Flight 46 Sideway Landing 8.3 - Theory of Flight 47 Cross Wind landing 8.3 - Theory of Flight 48 Balanced Turn 8.3 - Theory of Flight 49 Balanced Turn 8.3 - Theory of Flight 50 Turning Flight and The V-n Diagram Radial acceleration Curved flight path No Turning flight Change in the altitude 1 Level turn (Coordinated turn) Constant 2 Pull-up Increase 3 Pull-down Decrease 1. Level turn (Coordinated turn) Constant altitude Constant altitude Level turn (Coordinated turn) Symbol Physical meaning Resultant force Turn radius Bank angle (Angle of bank) Level turn Symbol Physical meaning Turn rate Turn radius Level turn 1. The lift vector is inclined at bank angle to the vertical. 2. The component of the lift in the vertical direction exactly equals the weight. Maintain constant altitude Level turn Resultant force (Fr) (Pythagorean theorem) (6.114) Load Factor 8.3 - Theory of Flight 57 Level Turn Load factor 1. The ratio between lift and weight. (L/W) 2. Usually quoted in terms of “g’s”. 3. 5G maneurver L/W=5 (6.115) (6.115) Load Factor 8.3 - Theory of Flight 59 Load Factor 8.3 - Theory of Flight 60 Load Factor During a Turn 8.3 - Theory of Flight 61 Load Factor Angle of Bank 8.3 - Theory of Flight 62 Load Factor Angle of Bank 8.3 - Theory of Flight 63 Load Factor Angle of Bank 8.3 - Theory of Flight 64 Wing Loading 8.3 - Theory of Flight 65 Wing Loading 8.3 - Theory of Flight 66 Wing Loading Stalling Speed 8.3 - Theory of Flight 67 “g” Limit 8.3 - Theory of Flight 68 How to survive high G force? 8.3 - Theory of Flight 69 “g” Limit from V-n diagram 8.3 - Theory of Flight 70 V-n diagram V-n diagram Maneuver point Structural limit + Corner velocity - Structural limit V-n diagram Low speed is a function of (limited by stall) V-n diagram (Low speed) Structural limit Structural limit Low speed is a function of (limited by stall) V-n diagram (High-speed) Structural limit Structural limit High speed is limited by structural design of the airplane Maneuver point Maneuver point Structural limit Structural limit 1. & are simultaneously at their highest possible values. 2. The smallest possible turn radius (R) & the largest possible turn rate (ω). Corner velocity Maneuver point Structural limit Corner velocity Structural limit 1. The velocity correspond to maneuver point. Corner velocity (6.134) 8.3 - Theory of Flight 79