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Design

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Design

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  1. Design Chapter 8 Second half

  2. Landing Gear Configuration • Tailwheel • PROS • simple to make & install • added very little weight and drag • CONS • complicates landing & taxiing operations • yawing tendency is amplified

  3. Landing Gear Configuration • Tricycle • PROS • CG is ahead of the main gear & adds stability on pitch & yaw motion • hard impact on nose gear causes a pitch down motion decreasing lift • yawing motion is counteracted by the forward CG • improved handling qualities • greater visibility

  4. Landing Gear Configuration • Tricycle • CONS • Nose gear has to withstand considerable impact • Its size and location add a fair amount of drag • The main gear is fairly aft and complicate attachment to the rest of the plane

  5. Tail Design • The purpose of the tail surfaces is to provide adequate stability and control. • The horizontal tail provides longitudinal stability and control • The vertical tail give the same qualities in the directional sense • The total horizontal tail surface provides longitudinal stability • The elevator provides pitch control • Rudder for yaw stability

  6. Tail Design • Conventional vertical tail • the single vertical fin mounted above the horizontal stabilizer • a large fin can result in significant rolling moment from rudder deflection • Twin vertical fin • two smaller fins and contribute to directional stability • endplate effect on the horizontal stabilizer make it more efficient

  7. Tail Design • T-Tail • purpose/advantage • to place it out of the wing’s downwash • downwash reduces the stabilizing effect of the horizontal tail & this is greater at high angles of attack • at full stall the downwash ceases and the wing’s wake flows directly aft.

  8. Tail Design • T-Tail Disadvantages • The T-tail experiences a sudden loss of effectiveness and a rapid pitch-down motion results in a deep stall. • T-tail also has the additional weight required for heavier structure necessary to support the horizontal tail in this position

  9. Tail Design • V-Tail • A single surface on either side of the centerline is canted upward to provide horizontal and vertical tail effects • the vertical projection provides longitudinal stability • the horizontal projection provides directional stability • This arrangement reduced the drag slightly over the conventional tail arrangement

  10. Tail Design • V-Tail • CONS • The main objection is the extremely complex control system required to get pitch and yaw control from a single control surface. • The V-tail is also susceptible to Dutch roll tendencies

  11. V-Tail & T-Tail • Both popular on sailplanes to keep the tail surfaces high to keep from being damaged in landing • Both also have good spin recovery characteristics

  12. First Estimation • Weight • best place to start is gross weight; so many other parameters depend on this value • figure 8-15 p. 235, Table 8-1 p.236 • Wing • wing loading or weight to wing area ratio

  13. First Estimation • Power • power required, horsepower • Range • fuel consumption

  14. Initial Estimation Example • Page 240-243 • Payload • Cruise • Range • Certifiable under FAR part 23

  15. Computer-Aided Design • Aerodynamic engineers use computers to model flow patterns. • Panel Method: • Three-dimensional bodies can be molded as a collection of flat panels and fluid flow relations applied to each of these panels. • Figure 8-17 p. 245 • Finite element methods simulate large structure with small elements connected by nodes.

  16. Quiz on Chapter 8 Take out a sheet of paper Include today’s date and your name

  17. Quiz on Chapter 8 • Compare and contrast the t-tail and the v-tail. • Why do aerodynamic engineers use Computer aided design (CAD)?