Theory of Flight – Part 2 PDF

Theory of Flight – Part 2 8.3 - Theory of Flight 1 Lift Augmentation 8.3 - Theory of Flight 2 Lift Augmentation 8.3 - Theory of Flight 3 Lift Augmentation - Slats 8.3 - Theory of Flight 4 Lift Augmentation - Sla...

Theory of Flight – Part 2 8.3 - Theory of Flight 1 Lift Augmentation 8.3 - Theory of Flight 2 Lift Augmentation 8.3 - Theory of Flight 3 Lift Augmentation - Slats 8.3 - Theory of Flight 4 Lift Augmentation - Slats 8.3 - Theory of Flight 5 Lift Augmentation 8.3 - Theory of Flight 6 Deflection of flap Increase in lift The increase in lift is due to 1. An effective increase in camber 2. A virtual increase in angle of attack  The impact of high lift device 1. is increased. 2. is shifted to more negative value. 3. The lift curve shifts to the left. 4. is decreased 5. (lift slope) remains unchanged. Aerodynamics Effect of Types of flap models Two figures of merit that are used to judge the quality of a given airfoil 1. L/D (The lift to drag ratio) - Represent aerodynamic efficiency. - Important for flight performance. - The range of the aircraft is directly proportional to L/D. 2. (The maximum lift coefficient) - determines the of the aircraft. - affects the field performance. (Take off & landing) Flaps Theory and Types Effect of Flaps Types of Flaps Plain flap Split flap Slotted flap Multi-element Fowler flap Slat Slat Example 1: Consider the Lockheed F-104 shown in the photograph below. With a full load of fuel, the airplane weights 10,258 kgf. Its empty weight (without fuel) is 6,071 kgf. The wing area is 18.21 m2. The wing of the F-104 is very thin, with a thickness of 3.4 %, and has a razor-sharp leading edge, both designed to minimize wave drag at supersonic speeds. A thin wing with a sharp leading edge, however, has very poor low-speed aerodynamic performance; such wings tend to stall at low angle of attack, thus limiting the maximum lift coefficient. The F-104 has both leading-edge and trailing edge flaps; but in spite of these high-lift devices, the maximum lift coefficient at subsonic speeds is only 1.15. Calculate the stalling speed at standard sea level when the airplane has (a) a full fuel tank and (b) an empty fuel tank. Compare the results. Lockheed F-104G (Luftwaffe) Solution (a) A full fuel tank From section 2.4 Therefore At sea level Stall speed Solution (b) An empty fuel tank Weight Stall speed Weight Vstall Empty Fuel tank 68.11 m/s Full Fuel tank 88.53 m/s Solution The trailing edge flap of Boeing 727 Streamline patterns over the Boeing 727 airfoil Example 2: Consider the Boeing 727 trijet transport shown in the photograph below. This airplane was designed in the 1960s to operate out of airports with relatively short runways, bringing jet service to smaller municipal airports. To minimize the takeoff and landing distances, the 727 had to designed with a relatively low Vstall. From Eq. (5.71), a low Vstall can be achieved by designing a wing with a large planform area (S), and / or with a very high value of CL,max. A large wing area, however, leads to structurally heavier wing and increased skin friction drag-both undesirable features. The Boeing engineers instead opted to achieve the highest possible CL,max by designing the most sophisticated high-lift mechanism at that time, consisting of triple-slotted flaps at the wing trailing edge and flaps and slots at the leading edge. With these devices fully deployed, the Boeing 727 had a maximum lift coefficient of 3.0. For a weight of 160,000 lb and a wing planform area of 1,650 ft2, calculate the staling speed of the Boeing 727 at standard sea level. Compare this result with that obtained for the F-104 in previous Example 1 Boeing 727 trijet Solution Trailing edge flap A portion of the trailing-edge section of the airfoil that is hinged and which can be deflected upward and downward. As the flap is deflected downward, the lift curve simply translates to the left Trailing edge flap Camber + More positive Increased More negative - More negative decreased More positive is a function of the amount of camber. TE flap deflection changes the camber of wing. (camber modifier) 1. At a given , the is increased by an amount. 2. The actual value of is increased. 3. is slightly decreased High Lift Device Flap hinge The flap hinge fairing of a slotted flap (DC-10) Extended flap - B727 Flap track fairing (A340-600) Flap track fairing Fuel dumping port Flap track fairing (A340-600) Leading-edge high-lift device 1. A thin, curved surface that is deployed in front of the leading edge. 2. Increase yields a higher Leading Edge High-lift Devices The effect of leading edge slat (NACA 4412) The effect of leading-edge slat defection 1. The lift curve is simply extended to a higher. 2. There is no change in. The Effect of High Lift Devices The effect of high lift devices The Effect of High Lift Devices The effect of high lift devices (DC-9) Leading Edge slat / leading-edge droop/ leading-edge flap General constraints on the design of high-lift multi-element airfoil sections Three Configurations of High-lift Devices No deployment of high-lift devices Partially deployed (thrust: maximum) Fully extended (thrust: idle) The driving mechanism of slat The driving mechanism of slat Leading edge high lift devices A380 B747 Leading edge high lift devices Kruger Flap – B737 Kruger flap (B737) Kruger Flap VS Fowler Flap Kruger flap Fowler flap Slat driving mechanism (using slat track) Conclusion 8.3 - Theory of Flight 43 8.3 - Theory of Flight 44