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aircraft:tmd:propeller

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Propeller

A propeller rotates around a spinning driveshaft which acts a torque onto the propeller. In the Aerofly FS 2 there are two kinds of propellers: the propeller class implements a propeller behavior in a rotating reference frame, attached to a rotating PropellerBody (rigidbody) whilst an aeropropeller uses a stationary Body and rotates itself. In all default Aerofly FS 2 aircraft only the propeller class is used.

Attributes

Body and EngineRotationSpeed

A propeller object will use the velocity of its Body (rigidbody) and the EngineRotationSpeed from the driveshaft and calculate a thrust value from that and a torque value to create that amount of thrust. It then adds that force and torque onto the Body which will accelerate/decelerate the body and speed it up or slow it down over time.

R0, X0, Y0, Z0

The position of the propeller hub is defined by the R0 position vector.

  • X0 is the local forward,
  • Y0 is the local left,
  • Z0 is the local upwards direction.

In the example of the Extra 330 LX below the propeller is slightly angled to the right (side thrust).

Airfoil

The same airfoil class is used for the aerowing and the propeller class. Using the properties of the AirfoilPropeller it is possible to fine-adjust the torque and thrust produced by the propeller. A typical propeller airfoil is designed for a lift coefficient of about 0.5.

Radius

The Radius of the propeller class is the physical radius of the actuator disk in meters. When converting from inches to meters simply multiply the radius in inches by 0.0254 m/inch. The radius of the propeller is of course half the diameter, which is usually given in the specifications.

Radius = 0.5 * Diameter

Pitch

The pitch of a propeller is roughly the blade angle at 75% of the radius. The pitch is the distance in meters that the propeller corkscrews through the air in one full rotation (geometrically). If a propeller pitch is given in inches multiply that figure by 0.0254 m/inch to convert it to the meter length unit used here. With a given blade angle (alpha) and a radius ® the blade pitch is calculated to:

Pitch = 2 * pi * r * tan(alpha)

PitchControl

The name is self-descriptive here. A input can be given to change the pitch of a propeller. That way a constant speed propeller can be controlled by a governor, reversed into beta or reverse thrust or feathered.

AspectRatio

The AspectRatio of a propeller is a factor that can be used to influence the rotationspeed - velocity relation ship. Physically it describes the ratio of the blade radius and the mean chord length of a blade.

Example Code

Simple Fixed Propeller

        <[string8][object][propeller]
            <[string8][Name][Propeller]>
            <[string8][Body][PropellerBody]>
            <[string8][EngineRotationSpeed][DriveShaft.GetRotationSpeed]>
            <[string8][DamageOnCrash]      [Engine.Damage]>
            <[tmvector3d][R0][0.0 0.0 0.0]>
            <[uint32][NumberBlades][2]>
            <[float64][Radius]      [1.00]>
            <[float64][Pitch]       [1.50]>
            <[string8][PitchControl][0.32]>
            <[float64][AspectRatio] [7.00]>
            <[float64][CutOut]      [0.20]>
            <[float64][LateralDragCoefficient] [0.005]>
            <[float64][LateralForceCoefficient][1.000]>
            <[float64][TorqueReduction][0.0]>
        >

Extra 330 LX - Constant Speed Propeller

Requires an airfoil object with the name AirfoilPropeller and a governor object with the name Governor
        <[string8][object][propeller]
            <[string8][Name][Propeller]>
            <[string8][Body][PropellerBody]>
            <[string8][Airfoil][AirfoilPropeller]>
            <[string8][EngineRotationSpeed][DriveShaft.GetRotationSpeed]>
            <[string8][DamageOnCrash]      [Engine.Damage]>
            <[tmvector3d][R0][1.9004   -0.0037    0.0064]>
            <[tmvector3d][X0][0.990279 -0.069798  0.000000]>
            <[tmvector3d][Y0][0.069798  0.990279 -0.000000]>
            <[tmvector3d][Z0][0.000000  0.000000  1.000000]>
            <[uint32][NumberBlades][3]>
            <[float64][Radius]      [0.99]>
            <[float64][Pitch]       [1.80]>
            <[string8][PitchControl][Governor.Output]>
            <[float64][AspectRatio] [9.00]>
            <[float64][CutOut]      [0.20]>
            <[float64][LateralDragCoefficient] [0.005]>
            <[float64][LateralForceCoefficient][1.000]>
            <[float64][TorqueReduction][0.0]>
        >
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aircraft/tmd/propeller.1485207046.txt.gz · Last modified: 2017/01/23 22:30 by jh