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=== Notes === | === Notes === | ||
FGElectric models an electric motor based on the configuration file <power> parameter. The throttle controls motor output linearly from zero to <power>. This power value (converted internally to horsepower) is then used by FGPropeller to apply torque to the propeller. At present there is no battery model available, so this motor does not consume any energy. There is no internal friction. | FGElectric models an electric motor based on the configuration file <power> parameter. The throttle controls motor output linearly from zero to <power>. This power value (converted internally to horsepower) is then used by FGPropeller to apply torque to the propeller. At present there is no battery model available, so this motor does not consume any energy. There is no internal friction. | ||
== FGRotor== | |||
Models a helicopter rotor. | |||
=== Configuration File Format === | |||
<syntaxhighlight lang="xml"> | |||
<rotor name="{string}"> | |||
<diameter unit="{LENGTH}"> {number} </diameter> | |||
<numblades> {number} </numblades> | |||
<gearratio> {number} </gearratio> | |||
<nominalrpm> {number} </nominalrpm> | |||
<minrpm> {number} </minrpm> | |||
<maxrpm> {number} </maxrpm> | |||
<chord unit="{LENGTH}"> {number} </chord> | |||
<liftcurveslope Xunit="1/RAD"> {number} </liftcurveslope> | |||
<twist unit="{ANGLE}"> {number} </twist> | |||
<hingeoffset unit="{LENGTH}"> {number} </hingeoffset> | |||
<flappingmoment unit="{MOMENT}"> {number} </flappingmoment> | |||
<massmoment Xunit="SLUG*FT"> {number} </massmoment> | |||
<polarmoment unit="{MOMENT}"> {number} </polarmoment> | |||
<inflowlag> {number} </inflowlag> | |||
<tiplossfactor> {number} </tiplossfactor> | |||
<maxbrakepower unit="{POWER}"> {number} </maxbrakepower> | |||
<gearloss unit="{POWER}"> {number} </gearloss> | |||
<gearmoment unit="{MOMENT}"> {number} </gearmoment> | |||
<controlmap> {MAIN|TAIL|TANDEM} </controlmap> | |||
<ExternalRPM> {number} </ExternalRPM> | |||
<groundeffectexp> {number} </groundeffectexp> | |||
<groundeffectshift unit="{LENGTH}"> {number} </groundeffectshift> | |||
</rotor> | |||
</syntaxhighlight> | |||
LENGTH means any of the supported units, same for ANGLE and MOMENT. | |||
Xunit-attributes are a hint for currently unsupported units, so values must be provided accordingly. | |||
=== Configuration Parameters: === | |||
Brief description and the symbol frequently found in the literature. | |||
<diameter> - Rotor disk diameter (2x R). | |||
<numblades> - Number of blades (b). | |||
<gearratio> - Ratio of (engine rpm) / (rotor rpm), usually > 1. | |||
<nominalrpm> - RPM at which the rotor usally operates. | |||
<minrpm> - Lowest RPM used in the model, optional and defaults to 1. | |||
<maxrpm> - Largest RPM used in the model, optional and defaults to 2 x nominalrpm. | |||
<chord> - Blade chord, (c). | |||
<liftcurveslope> - Slope of curve of section lift against section angle of attack, | |||
per rad (a). | |||
<twist> - Blade twist from root to tip, (theta_1). | |||
<hingeoffset> - Rotor flapping-hinge offset (e). | |||
<flappingmoment> - Flapping moment of inertia (I_b). | |||
<massmoment> - Blade mass moment. Mass of a single blade times the blade's | |||
cg-distance from the hub, optional. | |||
<polarmoment> - Moment of inertia for the whole rotor disk, optional. | |||
<inflowlag> - Rotor inflow time constant, sec. Smaller values yield to quicker | |||
responses (typical values for main rotor: 0.1 - 0.2 s). | |||
<tiplossfactor> - Tip-loss factor. The Blade fraction that produces lift. | |||
Value usually ranges between 0.95 - 1.0, optional (B). | |||
<maxbrakepower> - Rotor brake, 20-30 hp should work for a mid size helicopter. | |||
<gearloss> - Friction in gear, 0.2% to 3% of the engine power, optional (see notes). | |||
<gearmoment> - Approximation for the moment of inertia of the gear (and engine), | |||
defaults to 0.1 * polarmoment, optional. | |||
<controlmap> - Defines the control inputs used (see notes). | |||
<ExternalRPM> - Links the rotor to another rotor, or an user controllable property. | |||
==== Experimental properties: ==== | |||
<groundeffectexp> - Exponent for ground effect approximation. Values usually range from 0.04 | |||
for large rotors to 0.1 for smaller ones. As a rule of thumb the effect | |||
vanishes at a height 2-3 times the rotor diameter. | |||
formula used: exp ( - groundeffectexp * (height+groundeffectshift) ) | |||
Omitting or setting to 0.0 disables the effect calculation. | |||
<groundeffectshift> - Further adjustment of ground effect, approx. hub height or slightly above | |||
(This lessens the influence of the ground effect). | |||
== Sources == | == Sources == | ||