<rotor name="main" 
        x="2.218" y="0.0" z="1.605" 
        nx="0.05" ny="0" nz="1"
        fx="0.99" fy="0" fz="-0.043" 
        ccw="1"
        phi0="45"
        maxcollective="13"
        mincollective="0.3"
        mincyclicele="-9.5"
        maxcyclicele="9.5"
        mincyclicail="-2.5"
        maxcyclicail="2.7"
        diameter="10.1"
        numblades="2"
        weightperblade="60"
        relbladecenter="0.5"
        dynamic="1"
        rpm="495"
        rellenflaphinge="0.2"
        delta3="0.0"
        delta=".25"
        pitch-a="10"
        pitch-b="15"
        flapmin="-13.0"
        flapmax="13.0"
        flap0="-2.0"
        flap0factor="0"
        notorque="0"
        dragfactor="0.30"
        translift-ve="20"
        translift-maxfactor="0.7"
        ground-effect-constant="0.1"
        twist="-8.5"
        taper="1"
        chord="0.18288"
        number-of-segments="8"
        number-of-parts="8"
        rel-len-where-incidence-is-measured="0.7"
        rel-len-blade-start="0.04"
        airfoil-lift-coefficient="5.67"
        airfoil-drag-coefficient0="0.01"
        airfoil-drag-coefficient1="0.05"
        incidence-stall-zero-speed="19"
        incidence-stall-half-sonic-speed="10"
        lift-factor-stall="0.18"
        stall-change-over="5.5"
        drag-factor-stall="2.0"
        cyclic-factor="1.0"
        rotor-correction-factor="0.9">
        <control-input axis="/controls/flight/aileron-trim" control="CYCLICAIL" split="true"/>
        <control-input axis="/controls/flight/fcs/roll" control="CYCLICAIL" src0="-1.0" src1="1.0" dst0="-1.0" dst1="1.0"/>
        <control-input axis="/controls/flight/elevator-trim" control="CYCLICELE" split="true"/>
        <control-input axis="/controls/flight/fcs/pitch" control="CYCLICELE" src0="-1.0" src1="1.0" dst0="-1.0" dst1="1.0"/>
        <control-input axis="/controls/engines/engine[0]/throttle" control="COLLECTIVE" src0="0.0" src1="1.0" dst0="1.0" dst1="-1.0"/>
 </rotor>

rotor:    A rotor. Used for simulating helicopters. You can have one, two
         or even more.
         There is a drawing of a rotor in the Doc-directory
         (README.yasim.rotor.png) Please find the measures from this drawing
         for several parameters in square brackets [].
         If you specify a rotor, you do not need to specify a wing or hstab,
         the settings for approach and cruise will be ignored then. You have
         to specify the solver results manually. See below.
         The rotor generates downwash acting on all stabs, surfaces and
         fuselages. For all fuselages in the rotor downwash you should
         specify idrag="0" to get realistic results.

         name:    The name of the rotor.
                  (some data is stored at /rotors/name/)
                  The rpm, cone angle, yaw angle and roll angle are stored
                  for the complete rotor. For every blade the position
                  angle, the flap angle and the incidence angle are stored.
                  All angles are in degree, positive values always mean "up".
                  This is not completely tested, but seem to work at least
                  for rotors rotating counterclockwise.
                  A value stall gives the fraction of the rotor in stall
                  (weighted by the fraction the have on lift and drag
                  without stall). Use this for modifying the rotor-sound.
         x,y,z:   The position of the rotor center
         nx,ny,nz: The normal of the rotor (pointing upwards, will be
                  normalized by the computer)
         fx,fy,fz: A Vector pointing forward, if not perpendicular to the
                  normal it will be corrected by the computer
         diameter: The diameter in meter [D]
         numblades: The number of blades
         weightperblade: The weight per blade in pounds
         relbladecenter: The relative center of gravity of the blade. Maybe
                  not 100% correct interpreted; use 0.5 for the start and
                  change in small steps [b/R]
         chord:     The chord of the blade its base, along the X axis
                    (not normal to the leading edge, as it is
                    sometimes defined). [c]
         twist:     The difference between the incidence angle at the
                    blade root and the incidence angle at the wing
                    tip.  Typically, this is a negative number so
                    that the rotor tips have a lower angle of attack.
         taper:     The taper fraction, expressed as the tip chord
                    divided by the root chord.  A taper of one is a
                    bar blade, and zero would be a blade ending
                    at a point.  Defaults to one. [d/c]
         rel-len-where-incidence-is-measured: If the blade is twisted,
                    you need a point where to measure the incidence angle.
                    Zero means at the base, 1 means at the tip. Typically
                    it should be something near 0.7
         rel-len-blade-start: Typically the blade is not mounted in the
                  center of the rotor [a/R]
         rpm:     rounds per minute.
         phi0:    initial position of this rotor
         ccw:     determines if the rotor rotates clockwise (="0") or
                  counterclockwise (="1"), (if you look on the top of the
                  normal, so the bo105 has counterclockwise rotor).
                  "true" and "false" are not any longer supported to
                  increase my lifespan. ;-)
         maxcollective: The maximum of the collective incidence in degree
         mincollective: The minimum of the collective incidence in degree
         maxcyclicele: The maximum of the cyclic incidence in degree for
                  the elevator like function
         mincyclicele: The minimum of the cyclic incidence in degree for
                  the elevator like function
         maxcyclicail: The maximum of the cyclic incidence in degree for
                  the aileron like function
         mincyclicail: The minimum of the cyclic incidence in degree for
                  the aileron like function
         airfoil-incidence-no-lift: non symmetric airfoils produces lift
                  with no incidence. This is is the incidence, where the
                  airfoil is producing no lift. Zero for symmetrical airfoils
                  (default)
         incidence-stall-zero-speed:
         incidence-stall-half-sonic-speed: the stall incidence is a function
                  of the speed. I found some measured data, where this is
                  linear over a wide range of speed. Of course the linear
                  region ends at higher speeds than zero, but just
                  extrapolate the linear behavior to zero.
         lift-factor-stall: In stall airfoils produce less lift. Without
                  stall the c-lift of the profile is assumed to be
                  sin(incidence-"airfoil-incidence-no-lift")*liftcoef;
                  And in stall:
                  sin(2*(incidence-"airfoil-incidence-no-lift"))*liftcoef*...
                  ..."lift-factor-stall";
                  Therefore this factor is not the quotient between lift
                  with and without stall. Use 0.28 if you have no idea.
         drag-factor-stall: The drag of an airfoil in stall is larger than
                  without stall.
                  Without stall c-drag is assumed to be
                  abs(sin(incidence-"airfoil-incidence-no-lift"))...
                  ..*dragcoef1+dragcoef0);
                  With stall this is multiplied by drag-factor
         stall-change-over: For incidence<"incidence-stall" there is no stall.
                  For incidence>("incidence-stall"+"stall-change-over") there
                  is stall. In the range between this incidences it is
                  interpolated linear.

         pitch-a:
         pitch-b: collective incidence angles, If you start flightgear
                  with --log-level=info, flightgear reports lift and needed
                  power for theses incidence angles
         forceatpitch-a:
         poweratpitch-b:
         poweratpitch-0: old tokens, not supported any longer, the result are
                  not exactly the expected lift and power values. Will be
                  removed in one of the next updates.directly.Use "real"
                  coefficients instead (see below) and adjust the lift with
                  rotor-correction-factor.

         The airfoil of the rotor is described as follows:
         The way is to define the lift and drag coefficients directly.
         Without stall the c-lift of the profile is assumed to be
                  sin(incidence-"airfoil-incidence-no-lift")*liftcoef;
         And in stall:
                  sin(2*(incidence-"airfoil-incidence-no-lift"))*liftcoef*...
                  ..."lift-factor-stall";
         Without stall c-drag is assumed to be
                  abs(sin(incidence-"airfoil-incidence-no-lift"))...
                  ..*dragcoef1+dragcoef0);
         See above, how the coefficients are defined with stall.
         The parameters:
         airfoil-lift-coefficient: liftcoef
         airfoil-drag-coefficient0: dragcoef0
         airfoil-drag-coefficient1: dragcoef1
                  To find the right values: see README.yasim.rotor.ods
                  (Open Office file) or README.yasim.rotor.xls (Excel
                  file). With theses files you can generate graphs of the
                  airfoil coefficients and adjust the parameters to match
                  real airfoils. For many airfoils you find data published
                  in the internet. Parameters for the airfoils NACA 23012
                  (main rotor of bo105) and NACA 0012 (tail rotor of bo105?)
                  are included.

         rotor-correction-factor:
                  If you calculate the lift of a heli rotor or even of a
                  propeller, you get a value larger than the real measured
                  one. (Due to vortex effects.) This is considered in the
                  simulation, but with a old theory by Prantl, which is known
                  to give still too large. This is corrected by this token,
                  default: 1
         flapmin: Minimum flapping angle. (Should normally never reached)
         flapmax: Maximum flapping angle. (Should normally never reached)
         flap0:   Flapping angle at no rotation, i.e. -5
         dynamic: this changes the reactions speed of the rotor to an input.
                  normally 1 (Maybe there are rotors with a little faster
                  reaction, than use a value a little greater than one.
                  A value greater than one will result in a more inert,
                  system. Maybe it's useful for simulating the rotor of the
                  Bell UH1
         rellenflaphinge: The relative length from the center of the rotor
                  to the flapping hinge. Can be taken from pictures of the
                  helicopter (i.e. 0 for Bell206, about 0.05 for most
                  rotors) For rotors without flapping hinge (where the blade
                  are twisted instead, i.e. Bo 105, Lynx) use a mean value,
                  maybe 0.2. This value has a extreme result in the behavior
                  of the rotor [F/r]
         sharedflaphinge: determines, if the rotor has one central flapping
                  hinge (="1") for the blades (like the Bell206 or the tail
                  rotor of the Bo 105), default is "0".
         delta3: Some rotors have a delta3 effect, which results in a
                  decreasing of the incidence when the rotor is flapping.
                  A value of 0 (as most helicopters have) means no change in
                  incidence, a value of 1 result in a decreases of one degree
                  per one degree flapping.
                  So delta3 is the proportional factor between flapping and
                  decrease of incidence. I.e. the tail rotor of a Bo105 has
                  a delta3 of 1.
                  In some publications delta3 is described by an angle. The
                  value in YASim is the atan of this angle
         delta:   A factor for the damping constant for the flapping. 1 means
                  a analytical result, which is only a approximation. Has a
                  very strong result in the reaction of the rotor system on
                  control inputs.
                  If you know the flapping angle for a given cyclic input you
                  can adjust this by changing this value. Or if you now the
                  maximum roll rate or ...
         translift-maxfactor: Helicopters have "translational lift", which
                  is due to turbulence. In forward flying the rotor gets less
                  turbulence air and produces more lift. The factor is the
                  quotient between lift at high airspeeds to the lift at
                  hover (with same pitch).
         translift-ve: the speed, where the translational lift reaches 1/e of
                  the maximum value. In m/s.
         ground-effect-constant: Near to the ground the rotor produces more
                  torque than in higher altitudes. The ground effect is
                  calculated as
                  factor = 1+diameter/altitude*"ground-effect-constant"
         number-of-parts:
         number-of-segments: The rotor is simulated in "number-of-parts"
                  different directions.
                  In every direction the rotor is simulated at
                  number-of-segments points. If the value is to small, the
                  rotor will react unrealistic. If it is to high, cpu-power
                  will be wasted. I now use a value of 8 for
                  "number-of-parts" and 8 for number-of-segments for the main
                  rotor and 4 for "number-of-parts" and 5 for
                  "number-of-segments" for the tail rotor.
                  "number-of-parts" must be a multiple of 4 (if not, it
                  is corrected)
         cyclic-factor: The response of a rotor to cyclic input is hard to
                  calculate (its a damped oscillator in resonance, some
                  parameters have very large impact to the cyclic response)
                  With this parameter (default 1) you can adjust the
                  simulator to the real helo.
         downwashfactor: A factor for the downwash of the rotor, default 1.
         balance: The balance of the rotor. 1.0: the rotor is 100% balanced,
                  0.0: half of the blades are missing. Use a value near one
                  (0.98 ... 0.999) to add some vibration.
         tiltcenterx:
         tiltcentery:
         tiltcenterz: The center for the tilting of the complete rotorhead/
                      mast. Can be used for simulating of the Osprey or small
                      autogyros.
         mintiltyaw:
         mintiltpitch:
         mintiltroll:
         maxtiltyaw:
         maxtiltpitch:
         maxtiltroll: The limits (in degree) for tilting the rotor head

         All rotor can have <control> subelements for the cyclic
         (CYCLICELE, CYCLICAIL) and collective (COLLECTIVE) input.
         and can have <control> subelements for the tilting the whole rotor
         head around the y-axis (TILTPITCH), the x-axis (TILTROLL) and the
         z-axis (TILTYAW). ROTORBALANCE is a factor for the balance.