When it is lowered a slot is also formed between the

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When it is lowered a slot is also formed between the leading edge of the flap and the trailing edge of the wing. Air will flow and accelerate up through the two slots, reducing turbulence over the flap and over the wing generally. This type of flap will increase lift by 100% on that part of the wing where the flap is fitted. It also causes a large rearward movement of the centre of pressure. This type of flap may be found on propeller driven types.
Figure 36 Double Slotted Extension Flap
Aircraft Aerodynamics, Structures & Systems Module 13 B2, Book 1 of 9 ________________________________________________________________________________ ________________________________________________________________________________ Issue No. 0 Page 41 Date: January 09Figure 37 Slotted Extension Flaps fitted to a Propeller driven Aircraft Slat and Slotted Extension Flaps By adding a slat to the leading edge of the wing the lift can be further increased. Using a slat and double slotted extension flap will increase the lift of the basic aerofoil by 120%. The slat will also prevent the large rearward shift of the centre of pressure caused by extension flaps.
Aircraft Aerodynamics, Structures & Systems Module 13 B2, Book 1 of 9 ________________________________________________________________________________ ________________________________________________________________________________ Issue No. 0 Page 42 Date: January 09Figure 39 Leading Edge Slat Vane and Auxiliary Flap in Landing Position Figure 38 Slat and Double Slotted Extension Flap
Aircraft Aerodynamics, Structures & Systems Module 13 B2, Book 1 of 9 ________________________________________________________________________________ ________________________________________________________________________________ Issue No. 0 Page 43 Date: January 09Figure 40 Triple Slotted Flap in various positions Figure 41 The effects of Flaps and Slots on Maximum lift coefficient and Stalling Angle
Aircraft Aerodynamics, Structures & Systems Module 13 B2, Book 1 of 9 ________________________________________________________________________________ ________________________________________________________________________________ Issue No. 0 Page 44 Date: January 09General The high lift required for the take-off and landing of large jet transports is normally provided by the combined effect of leading edge high lift devices and trailing edge flaps. Propeller driven types do not normally use leading edge high lift devices. Sufficient lift is provided by trailing edge flaps and the propeller slipstream over the mainplanes. For take-off the flaps are lowered to a small angle. This gives extra lift and a small increase in drag. For landing, the flaps are lowered too much larger angles to increase lift and drag which will help to slow the aircraft on the landing approach. Figure 42 Propeller Slipstream Increases Wing Lift Leading edge slats normally have two extended positions, take-off and landing. In the take-off position the slat is extended without forming a slot. Krueger flaps and variable camber flaps are either retracted of fully extended. They have no intermediate position. An aircraft will always take-off into wind, in order to reach flying speed with the shortest ground run. It will also land into wind so that it can touch down with the lowest ground speed. This will allow it to stop in the shortest distance.
Aircraft Aerodynamics, Structures & Systems Module 13 B2, Book 1 of 9 ________________________________________________________________________________ ________________________________________________________________________________ Issue No. 0 Page 45 Date: January 09Figure 43 Layout of High Lift Devices
Aircraft Aerodynamics, Structures & Systems Module 13 B2, Book 1 of 9 ________________________________________________________________________________ ________________________________________________________________________________ Issue No. 0 Page 46 Date: January 09Figure 44 Trailing Edge Devices Protection of High Lift Devices

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