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Design. Chapter 8 Second half. Landing Gear Configuration. Tailwheel PROS simple to make & install added very little weight and drag CONS complicates landing & taxiing operations yawing tendency is amplified. Landing Gear Configuration. Tricycle PROS

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Design l.jpg

Design

Chapter 8

Second half


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Landing Gear Configuration

  • Tailwheel

    • PROS

      • simple to make & install

      • added very little weight and drag

    • CONS

      • complicates landing & taxiing operations

      • yawing tendency is amplified


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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


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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


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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


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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


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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.


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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


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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


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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


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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


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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


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First Estimation

  • Power

    • power required, horsepower

  • Range

    • fuel consumption


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Initial Estimation Example

  • Page 240-243

  • Payload

  • Cruise

  • Range

  • Certifiable under FAR part 23


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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.


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Quiz on Chapter 8

Take out a sheet of paper

Include today’s date and your name


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Quiz on Chapter 8

  • Compare and contrast the t-tail and the v-tail.

  • Why do aerodynamic engineers use Computer aided design (CAD)?