fgdata/Docs/README.yasim

Coordinate system notes: All positions specified are in meters (which
is weird, since all other units in the file are English).  The X axis
points forward, Y is left, and Z is up.  Take your right hand, and
hold it like a gun.  Your first and second fingers are the X and Y
axes, and your upwards-pointing thumb is the Z.  This is slightly
different from the coordinate system used by JSBSim.  Sorry.  The
origin can be placed anywhere, so long as you are consistent.  I use
the nose of the aircraft.

XML Elements
------------

airplane: The top-level element for the file.  It contains only one
          attribute:
          mass: The empty (no fuel) weight, in pounds.

approach: The approach parameters for the aircraft.  The solver will
          generate an aircraft that matches these settings.  The element
          can (and should) contain <control> elements indicating pilot
          input settings, such as flaps and throttle, for the
          approach.
          speed: The approach airspeed, in knots TAS.
          aoa:   The approach angle of attack, in degrees
          fuel:  Fraction (0-1) of fuel in the tanks.  Default is 0.2.

cruise:   The cruise speed and altitude for the solver to match.  As
          above, this should contain <control> elements indicating
          aircraft configuration.  Especially, make sure the engines
          are generating enough thrust at cruise!
          speed: The cruise speed, in knots TAS.
          alt:   The cruise altitude, in feet MSL.
          fuel:  Fraction (0-1) of fuel in the tanks.  Default is 0.2.

cockpit:  The location of the cockpit (pilot eyepoint).
          x,y,z: eyepoint location (see coordinates note)

fuselage: This defines a tubelike structure.  It will be given an even
          mass and aerodynamic force distribution by the solver.  You
          can have as many as you like, in any orientation you please.
          ax,ay,az: One end of the tube (typically the front)
          bx,by,bz: The other ("back") end.
          width:    The width of the tube, in meters.
          taper:    The approximate radius at the "tips" of the fuselage
                    expressed as a fraction (0-1) of the width value.
          midpoint: The location of the widest part of the fuselage,
                    expressed as a fraction of the distance between A and B.
          idrag:    Multiplier for the "induced drag" generated by this
                    object. Default is one. With idrag=0 the fuselage
                    generates only drag.
          cx,cy,cz: Factors for the generated drag in the fuselages "local
                    coordinate system" with x pointing from end to front,
                    z perpendicular to x with y=0 in the aircraft coordinate
                    system. E.g. for a fuselage of a height of 2 times the
                    width you can define cy=2 and (due to the doubled front
                    surface) cx=2.

wing:     This defines the main wing of the aircraft.  You can have
          only one (but see below about using vstab objects for extra
          lifting surfaces).  The wing should have a <stall> subelement to
          indicate stall behavior, control surface subelements (flap0,
          flap1, spoiler, slat) to indicate what and where the control
          surfaces are, and <control> subelements to map user input
          properties to the control surfaces.
          x,y,z:     The "base" of the wing, specified as the location of
                     the mid-chord (not leading edge, trailing edge, or
                     aerodynamic center) point at the root of the LEFT
                     (!)  wing.
          length:    The length from the base of the wing to the midchord
                     point at the tip.  Note that this is not the same
                     thing as span.
          chord:     The chord of the wing at its base, along the X axis
                     (not normal to the leading edge, as it is
                     sometimes defined).
          incidence: The incidence angle at the wing root, in degrees.
                     Zero is level with the fuselage (as in an
                     aerobatic plane), positive means that the leading
                     edge is higher than the trailing edge (as in a
                     trainer).
          twist:     The difference between the incidence angle at the
                     wing root and the incidence angle at the wing
                     tip.  Typically, this is a negative number so
                     that the wing tips have a lower angle of attack
                     and stall after the wing root (washout).
          taper:     The taper fraction, expressed as the tip chord
                     divided by the root chord.  A taper of one is a
                     hershey bar wing, and zero would be a wing ending
                     at a point.  Defaults to one.
          sweep:     The sweep angle of the wing, in degrees.  Zero is
                     no sweep, positive angles are swept back.
                     Defaults to zero.
          dihedral:  The dihedral angle of the wing.  Positive angles
                     are upward dihedral.  Defaults to zero.
          idrag:     Multiplier for the "induced drag" generated by this
                     surface.  In general, low aspect wings will
                     generate less induced drag per-AoA than high
                     aspect (glider) wings.  This value isn't
                     constrained well by the solution process, and may
                     require tuning to get throttle settings correct in
                     high AoA (approach) situations.
          camber:    The lift produced by the wing at zero angle of
                     attack, expressed as a fraction of the maximum
                     lift produced at the stall AoA.

hstab:    These defines the horizontal stabilizer of the aircraft.
          Internally, it is just a wing object and therefore works the
          same in XML.  You are allowed only one hstab object; the
          solver needs to know which wing's incidence to play with to
          get the aircraft trimmed correctly.

vstab:    A "vertical" stabilizer.  Like hstab, this is just another
          wing, with a few special properties.  The surface is not
          "mirrored" as are wing and hstab objects.  If you define a
          left wing only, you'll only get a left wing.  The default
          dihedral, if unspecified, is 90 degrees instead of zero.
          But all parameters are equally settable, so there's no
          requirement that this object be "vertical" at all.  You can
          use it for anything you like, such as extra wings for
          biplanes.  Most importantly, these surfaces are not involved
          with the solver computation, so you can have none, or as
          many as you like.

mstab:    A mirrored horizontal stabilizer. Exactly the same as wing, but
          not involved with the solver computation, so you can have none,
          or as many as you like.

stall:    A subelement of a wing (or hstab/vstab/mstab) that specifies the
          stall behavior.
          aoa:   The stall angle (maximum lift) in degrees.  Note that
                 this is relative to the wing, not the fuselage (since
                 the wing may have a non-zero incidence angle).
          width: The "width" of the stall, in degrees.  A high value
                 indicates a gentle stall.  Low values are viscious
                 for a non-twisted wing, but are acceptable for a
                 twisted one (since the whole wing will not stall at
                 the same time).
          peak:  The height of the lift peak, relative to the
                 post-stall secondary lift peak at 45 degrees.
                 Defaults to 1.5.  This one is deep voodoo, and
                 probably doesn't need to change much.  Bug me for an
                 explanation if you're curious.

flap0, flap1, slat, spoiler:
          These are subelements of wing/hstab/vstab objects, and specify
          the location and effectiveness of the control surfaces.
          start:  The position along the wing where the control
                  surface begins.  Zero is the root, one is the tip.
          end:    The position where the surface ends, as above.
          lift:   The lift multiplier for a flap or slat at full
                  extension.  One is a no-op, a typical aileron might
                  be 1.2 or so, a giant jetliner flap 2.0, and a
                  spoiler 0.0.  For spoilers, the interpretation is a
                  little different -- they spoil only "prestall" lift.
                  Lift due purely to "flat plate" effects isn't
                  affected.  For typical wings that stall at low AoA's
                  essentially all lift is pre-stall and you don't have
                  to care.  Jet fighters tend not to have wing
                  spoilers, for exactly this reason.  This value is
                  not applicable to slats, which affect stall AoA
                  only.
          drag:   The drag multiplier, as above.  Typically should be
                  higher than the lift multiplier for flaps.
          aoa:    Applicable only to slats.  This indicates the
                  angle by which the stall AoA is translated by the
                  slat extension.

jet:      A turbojet/fan engine.  It accepts a <control> subelement to map a
          property to its throttle setting, and an <actionpt> subelement
          to place the action point of the thrust at a different
          position than the mass of the engine.
          x,y,z:          The location of the engine, as a point mass.
                          If no actionpt is specified, this will also
                          be the point of application of thrust.
          mass:           The mass of the engine, in pounds.
          thrust:         The maximum sea-level thrust, in pounds.
          afterburner:    Maximum total thrust with afterburner/reheat,
                          in pounds [defaults to "no additional
                          thrust"].
          rotate:         Vector angle of the thrust in degrees about the
                          Y axis [0].
          n1-idle:        Idling rotor speed [55].
          n1-max:         Maximum rotor speed [102].
          n2-idle:        Idling compressor speed [73].
          n2-max:         Maximum compressor speed [103].
          tsfc:           Thrust-specific fuel consumption [0.8].
                          This should be considerably lower for modern
                          turbofans.
          egt:            Exhaust gas temperature at takeoff [1050].
          epr:            Engine pressure ratio at takeoff [3.0].
          exhaust-speed:  The maximum exhaust speed in knots [~1555].
          spool-time:     Time, in seconds, for the engine to respond to
                          90% of a commanded power setting.

propeller: A propeller.  This element requires an engine subtag.
           Currently <piston-engine> and <turbine-engine> are
           supported.
           x,y,z:         The position of the mass (!) of the
                          engine/propeller combination.  If the point
                          of force application is different (and it
                          will be) it should be set with an <actionpt>
                          subelement.
           mass:          The mass of the engine/propeller, in pounds.
           moment:        The moment, in kg-meters^2.  This has to be
                          hand calculated and guessed at for now.  A
                          more automated system will be forthcoming.
                          Use a negative moment value for
                          counter-rotating ("European" -- CCW as seen
                          from behind the prop) propellers.
                          A good guess for this value is the radius of
                          the prop (in meters) squared times the mass
                          (kg) divided by three; that is the moment of
                          a plain "stick" bolted to the prop shaft.
           radius:        The radius, in meters, or the propeller.
           cruise-speed:  The max efficiency cruise speed of the
                          propeller.  Generally not the same as the
                          aircraft's cruise speed.
           cruise-rpm:    The RPM of the propeller at max-eff. cruise.
           cruise-power:  The power sunk by the prop at cruise, in horsepower.
           cruise-alt:    The reference cruise altitude in feet.
           takeoff-power: The takeoff power required by the propeller...
           takeoff-rpm:   ...at the given takeoff RPM.
           min-rpm:       The minimum operational RPM for a constant speed
                          propeller.  This is the speed to which the
                          prop governor will seek when the blue lever
                          is at minimum.  The coarse-stop attribute
                          limits how far the governor can go into trying
                          to reach this RPM.
           max-rpm:       The maximum operational RPM for a constant speed
                          propeller.  See above.  The fine-stop attribute
                          limits how far the governor can go in trying
                          to reach this RPM.
           fine-stop:     The minimum pitch of the propeller (high RPM) as a
                          ratio of ideal cruise pitch.  This is set to 0.25
                          by default -- a higher value will result in a
                          lower RPM at low power settings (e.g. idle, taxi,
                          and approach).
           coarse-stop:   The maximum pitch of the propeller (low RPM) as
                          a ratio of ideal cruise pitch.  This is set to
                          4.0 by default -- a lower value may result in a
                          higher RPM at high power settings.
           gear-ratio:    The factor by which the engine RPM is multiplied
                          to produce the propeller RPM.  Optional (defaults
                          to 1.0).
           contra:        When set (contra="1"), this indicates that the
                          propeller is a contra-rotating pair.  It
                          will not contribute to the aircraft's net
                          gyroscopic moment, nor will it produce
                          asymmetric torque on the aircraft body.
                          Asymmetric slipstream effects, when
                          implemented, will also be zero when this is
                          set.

piston-engine: A piston engine definition.  This must be a subelement
               of an enclosing <propeller> tag.
               eng-power:    Maximum BHP of the engine at sea level.
               eng-rpm:      The engine RPM at which eng-power is developed
               displacement: The engine displacement in cubic inches.
               compression:  The engine compression ratio.
               turbo-mul:    The turbo/super-charger pressure multiplier.
                             Static pressure will be multiplied by this
                             value to get the manifold pressure.
               wastegate-mp: The maximum manifold pressure.  Beyond
                             this, the gate will release to keep the
                             MP below this number. (inHG).  This value
                             can be changed at runtime using the
                             WASTEGATE control axis, which is a
                             multiplier in the range [0:1].
               turbo-lag:    Time lag, in seconds, for 90% of a power change
                             to be reflected in the turbocharger boost
                             pressure.

turbine-engine: A turbine engine definition.  This must be a subelement
                of an enclosing <propeller> tag.
                eng-power:   Maximum BHP of the engine at a suitable
                             cruise altitude.
                eng-rpm:     The engine RPM at which eng-power is
                             developed.  Note that this is "shaft" RPM
                             as seen by the propeller.  Don't use a
                             gear-ratio on the enclosing propeller, or
                             else you'll get confused. :)
                alt:         The altitude at which eng-power is developed.
                             This should be high enough to be lower (!)
                             than the flat-rating power.
                flat-rating: The maximum allowed power developed by
                             the engine.  Most turboprops are flat
                             rated below a certain altitude and
                             temperature range to prevent engine
                             damage.
                min-n2:      N2 (percent) turbine speed at zero throttle.
                max-n2:      N2 (percent) turbine speed at max throttle.
                bsfc:        Specific fuel consumption, in lbs/hr per
                             horsepower.


actionpt: Defines an "action point" for an enclosing jet or propeller
          element.  This is the location where the force from the thruster
          will be applied.
          x,y,z:  The location of force application.

gear:     Defines a landing gear.  Accepts <control> subelements to map
          properties to steering and braking. Can also be used to simulate
          floats. Although the coefficients are still called ..fric, it
          is calculated in fluids as a drag (proportional to the square
          of the speed). In fluids gears are not considered to detect
          crashes (as on ground).
          x,y,z:  The location of the fully-extended gear tip.
          compression:  The distance in meters along the "up" axis that
                        the gear will compress.
          initial-load: The initial load of the spring in multiples of
                        compression. Defaults to 0. (With this parameter
                        a lower spring-constants will be used for the
                        gear-> can reduce numerical problems (jitter))
                        Note: the spring-constant is varied from 0%
                        compression to 20% compression to get continuous
                        behavior around 0 compression. (could be physically
                        explained by wheel deformation)
          upx/upy/upz:  The direction of compression, defaults to
                        vertical (0,0,1) if unspecified.  These are
                        used only for a direction -- the vector need
                        not be normalized, as the length is specified
                        by "compression".
          sfric:        Static (non-skidding) coefficient of
                        friction.  Defaults to 0.8.
          dfric:        Dynamic friction.  Defaults to 0.7.
          spring:       A dimensionless multiplier for the automatically
                        generated spring constant.  Increase to make
                        the gear stiffer, decrease to make it
                        squishier.
          damp:         A dimensionless multiplier for the automatically
                        generated damping coefficient.  Decrease to
                        make the gear "bouncier", increase to make it
                        "slower".  Beware of increasing this too far:
                        very high damping forces can make the numerics
                        unstable.  If you can't make the gear stop
                        bouncing with this number, try increasing the
                        compression length instead.
          on-water:     if this is set to "0" the gear will be ignored if
                        on water. Defaults to "0"
          on-solid:     if this set to "0" the gear will be ignored if
                        not on water. Defaults to "1"
          speed-planing:
          spring-factor-not-planing:
                        At zero speed the spring factor is multiplied by
                        spring-factor-not-planing. Above speed-planing this
                        factor is equal to 1. The idea is, to use this for
                        floats simulating the transition from swimming to
                        planing. speed-planing defaults to 0,
                        spring-factor-not-planing defaults to 1.
          reduce-friction-by-extension: at full extension the friction is
                        reduced by this relative value. 0.7 means 30% friction
                        at full extension. If you specify a value greater
                        than one, the friction will be zero before reaching
                        full extension. Defaults to "0"
          ignored-by-solver: with the on-water/on-solid tags you can have more
                        than one set of gears in one aircraft, If the solver
                        (who automatically generates the spring constants)
                        would take all gears into account, the result would be
                        wrong. E. G. set this tag to "1" for all gears, which
                        are not active on runways. Defaults to "0". You can
                        not exclude all gears in the solving process.

launchbar: Defines a catapult launchbar or strop.
           x,y,z:      The location of the mount point of the launch bar or
                       strop on the aircraft.
           length:     The length of the launch bar from mount point to tip
           down-angle: The max angle below the horizontal the
                       launchbar can achieve.
           up-angle:   The max angle above the horizontal the launchbar
                       can achieve.
           holdback-{x,y,z}: The location of the holdback mount point
                             on the aircraft.
           holdback-length: The length of the holdback from mount
                            point to tip.  Note: holdback up-angle and
                            down-angle are the same as those defined
                            for the launchbar and are not specified in
                            the configuration.

tank:     A fuel tank.  Tanks in the aircraft are identified
          numerically (starting from zero), in the order they are
          defined in the file.  If the left tank is first, "tank[0]"
          will be the left tank.
          x,y,z:    The location of the tank.
          capacity: The maximum contents of the tank, in pounds.  Not
                    gallons -- YASim supports fuels of varying
                    densities.
          jet:      A boolean.  If present, this causes the fuel
                    density to be treated as Jet-A.  Otherwise,
                    gasoline density is used.  A more elaborate
                    density setting (in pounds per gallon, for
                    example) would be easy to implement.  Bug me.

ballast:  This is a mechanism for modifying the mass distribution of
          the aircraft.  A ballast setting specifies that a particular
          amount of the empty weight of the aircraft must be placed at
          a given location.  The remaining non-ballast weight will be
          distributed "intelligently" across the fuselage and wing
          objects.  Note again: this does NOT change the empty weight
          of the aircraft.
          x,y,z: The location of the ballast.
          mass:  How much mass, in pounds, to put there.  Note that
                 this value can be negative.  I find that I often need
                 to "lighten" the tail of the aircraft.

weight:   This is an added weight, something not part of the empty
          weight of the aircraft, like passengers, cargo, or external
          stores.  The actual value of the mass is not specified here,
          instead, a mapping to a property is used.  This allows
          external code, such as the panel, to control the weight
          (loading a given cargo configuration from preference files,
          dropping bombs at runtime, etc...)
          x,y,z:      The location of the weight.
          mass-prop:  The name of the fgfs property containing the
                      mass, in pounds, of this weight.
          size:       The aerodynamic "size", in meters, of the
                      object.  This is important for external stores,
                      which will cause drag.  For reasonably
                      aerodynamic stuff like bombs, the size should be
                      roughly the width of the object.  For other
                      stuff, you're on your own.  The default is zero,
                      which results in no aerodynamic force (internal
                      cargo).

solve-weight:
          Subtag of approach and cruise parameters.  Used to specify a
          non-zero setting for a <weight> tag during solution.  The
          default is to assume all weights are zero at the given
          performance numbers.
          idx:    Index of the weight in the file (starting with zero).
          weight: Weight setting in pounds.


control-input:
          This element manages a mapping from fgfs properties (user
          input) to settable values on the aircraft's objects.  Note
          that the value to be set MUST (!) be valid on the given
          object type.  This is not checked for by the parser, and
          will cause a runtime crash if you try it.  Wing's don't have
          throttle controls, etc...  Note that multiple axes may be
          set on the same value.  They are summed before setting.

          axis:  The name of the double-valued fgfs property "axis" to
                 use as input, such as "/controls/flight/aileron".
          control: Which control axis to set on the objects.  It can have
                   the following values:
                  THROTTLE - The throttle on a jet or propeller.
                  MIXTURE - The mixture on a propeller.
                  REHEAT - The afterburner on a jet
                  PROP - The propeller advance
                  BRAKE - The brake on a gear.
                  STEER - The steering angle on a gear.
                  INCIDENCE - The incidence angle of a wing.
                  FLAP0 - The flap0 deflection of a wing.
                  FLAP1 - The flap1 deflection of a wing.
                  SLAT - The slat extension of a wing.
                  SPOILER - The spoiler extension for a wing.
                  CYCLICAIL - The "aileron" cyclic input of a rotor
                  CYCLICELE - The "elevator" cyclic input of a rotor
                  COLLECTIVE - The collective input of a rotor
                  ROTORENGINEON - If not equal zero the rotor is rotating
                  WINCHRELSPEED - The relative winch speed
                  {... and many more, see FGFDM.cpp ...}
          invert: Negate the value of the property before setting on
                  the object.
          split:  Applicable to wing control surfaces.  Sets the
                  normal value on the left wing, and a negated value
                  on the right wing.
          square: Squares the value before setting.  Useful for
                  controls like steering that need a wide range, yet
                  lots of sensitivity in the center.  Obviously only
                  applicable to values that have a range of [-1:1] or
                  [0:1].
          src0/src1/dst0/dst1:
                  If present, these defined a linear mapping from the
                  source to the output value.  Input values in the
                  range src0-src1 are mapped linearly to dst0-dst1,
                  with clamping for input values that lie outside the
                  range.

control-output:
          This can be used to pass the value of a YASim control axis
          (after all mapping and summing is applied) back to the
          property tree.

          control: Name of the control axis.  See above.
          prop:    Property node to receive the value.
          side:    Optional, for split controls.  Either "right" or "left"
          min/max: Clamping applied to output value.

control-speed:
          Some controls (most notably flaps and hydraulics) have
          maximum slew rates and cannot respond instantly to pilot
          input.  This can be implemented with a control-speed tag,
          which defines a "transition time" required to slew through
          the full input range.  Note that this tag is
          semi-deprecated, complicated control input filtering can be
          done much more robustly from a Nasal script.

          control: Name of the control axis. See above.
          transition-time: Time in seconds to slew through input range.

control-setting:
          This tag is used to define a particular setting for a
          control axis inside the <cruise> or <approach> tags, where
          obviously property input is not available.  It can be used,
          for example, to inform the solver that the approach
          performance values assume full flaps, etc...

          axis:  Name of the control input (i.e. a property name)
          value: Value of the control axis.

hitch:    A hitch, can be used for winch-start (in gliders) or aerotow (in
          gliders and motor aircrafts) or for external cargo with helicopter.
          You can do aerotow over the net via multiplayer (see j3 and bocian
          as an example).
          
          name:  the name of the hitch. must be aerotow if you want to do
                 aerotow via multiplayer. You will find many properties
                 at /sim/hitches/name. Most of them are directly tied to
                 the internal variables, you can modify them as you like.
                 You can add a listener to the property "broken", e. g. for
                 playing a sound.
          x,y,z: The position of the hitch
          force-is-calculated-by-other: if you want to simulate aerotowing
                 over the internet, set this value to "1" in the motor
                 aircraft. Don't specify or set this to zero in gliders.
                 In a LAN the time lag might be small enough to set it on
                 both aircrafts to "0". It's intended, that this is done
                 automatically in the future.

tow: The tow used for aerotow or winch. This must be a subelement
               of an enclosing <hitch> tag.
          length: upstretched length in m
          weight-per-meter: in kg/m
          elastic-constant: lower values give higher elasticity
          break-force: in N
          mp-auto-connect-period: the every x seconds a towed multiplayer
                 aircraft is searched. If found, this tow is connected
                 automatically, parameters are copied from the other
                 aircraft. Should be set only in the motor aircraft, not
                 in the glider

winch: The tow used for aerotow or winch. This must be a subelement
               of an enclosing <hitch> tag.
          max-tow-length:
          min-tow-length:
          initial-tow-length: all are in m. The initial tow length also 
                 defines the length/search radius used for the mp-autoconnect
                 feature
          max-winch-speed: in m/s
          power: in kW
          max-force: in N


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.
          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.

          All rotor can have <control> subelements for the cyclic
          (CYCLICELE, CYCLICAIL) and collective (COLLECTIVE) input.

rotorgear: If you are using one ore more rotors you have to define a
          rotorgear. It connects all the rotors and adds a simple engine.
          In future it will be possible, to add a YASim-engine.
          max-power-engine: the maximum power of the engine, in kW.
          engine-prop-factor: the engine is working as a pd-regulator. This
                   is the width of the regulation-band, or, in other words,
                   the inverse of the proportional-factor of the regulator.
                   If you set it to 0.02, than up to 98% of the rotor-rpm
                   the engine will produce maximum torque. At 100% of
                   the engine will produce no torque.  It is planned to use
                   YASim-engines instead of this simple engine.
          engine-accel-limit: The d-factor of the engine is defined as the
                   maximum acceleration rate of the engine in %/s,
                   default is 5%/s.
          max-power-rotor-brake: the maximum power of the rotor brake, in kW
                   at normal rpm (most? real rotor breaks would be overheated
                   if used at normal rpm, but this is not simulated now)
          rotorgear-friction: the power loss due to friction in kW at normal
                   RPM
          yasimdragfactor:
          yasimliftfactor: the solver is not working with rotor-aircrafts.
                   Therefore you have to specify the results yourself.
                   10 for drag and 140 for lift seem to be good starting
                   values. Although the solve is not invoked for aircrafts
                   with at least one rotor, you need to specify the cruise
                   and the approach settings. The approach speed is needed to
                   calculate the gear springs. Use a speed of approx. 50knots.
                   They do not need to match any real value.

          The rotorgear needs a <control> subelement for the engine
          (ROTORGEARENGINEON) and can have furhter <control> subelements:
                   ROTORBRAKE: rotor brake
                   ROTORRELTARGET: the target rpm of the engine relative to
                               the "normal" value for the governor. Default is
                               1. Additionally you can modify this value in
                               the property tree (/rotors/gear/target-rel-rpm)
                               limited internally to 2.5
                   ROTORENGINEMAXRELTORQUE: the maximum torque of the engine
                               relativ to the torque defined by the engine-
                               power. Default is 1. By setting the rel-target
                               to a large number you get control over the
                               engine by this control.  Additionally you can
                               modify this value in the property tree
                               (/rotors/gear/max-rel-torque)
                               Alternativ you can use these two values for
                               individual start-up sequences (see the s58)

          The rotor simulation is still "beta".