458 lines
26 KiB
Text
458 lines
26 KiB
Text
Coordinate system notes: All positions specified are in meters (which
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is weird, since all other units in the file are English). The X axis
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points forward, Y is left, and Z is up. Take your right hand, and
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hold it like a gun. Your first and second fingers are the X and Y
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axes, and your upwards-pointing thumb is the Z. This is slightly
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different from the coordinate system used by JSBSim. Sorry. The
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origin can be placed anywhere, so long as you are consistent. I use
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the nose of the aircraft.
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XML Elements
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------------
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airplane: The top-level element for the file. It contains only one
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attribute:
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mass: The empty (no fuel) weight, in pounds.
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approach: The approach parameters for the aircraft. The solver will
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generate an aircraft that matches these settings. The element
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can (and should) contain <control> elements indicating pilot
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input settings, such as flaps and throttle, for the
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approach.
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speed: The approach airspeed, in knots TAS.
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aoa: The approach angle of attack, in degrees
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fuel: Fraction (0-1) of fuel in the tanks. Default is 0.2.
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cruise: The cruise speed and altitude for the solver to match. As
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above, this should contain <control> elements indicating
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aircraft configuration. Especially, make sure the engines
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are generating enough thrust at cruise!
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speed: The cruise speed, in knots TAS.
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alt: The cruise altitude, in feet MSL.
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fuel: Fraction (0-1) of fuel in the tanks. Default is 0.2.
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cockpit: The location of the cockpit (pilot eyepoint).
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x,y,z: eyepoint location (see coordinates note)
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fuselage: This defines a tubelike structure. It will be given an even
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mass and aerodynamic force distribution by the solver. You
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can have as many as you like, in any orientation you please.
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ax,ay,az: One end of the tube (typically the front)
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bx,by,bz: The other ("back") end.
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width: The width of the tube, in meters.
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taper: The approximate radius at the "tips" of the fuselage
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expressed as a fraction (0-1) of the width value.
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midpoint: The location of the widest part of the fuselage,
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expressed as a fraction of the distance between A and B.
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wing: This defines the main wing of the aircraft. You can have
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only one (but see below about using vstab objects for extra
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lifting surfaces). The wing should have a <stall> subelement to
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indicate stall behavior, control surface subelements (flap0,
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flap1, spoiler, slat) to indicate what and where the control
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surfaces are, and <control> subelements to map user input
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properties to the control surfaces.
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x,y,z: The "base" of the wing, specified as the location of
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the mid-chord (not leading edge, trailing edge, or
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aerodynamic center) point at the root of the LEFT
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(!) wing.
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length: The length from the base of the wing to the midchord
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point at the tip. Note that this is not the same
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thing as span.
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chord: The chord of the wing at its base, along the X axis
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(not normal to the leading edge, as it is
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sometimes defined).
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incidence: The incidence angle at the wing root, in degrees.
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Zero is level with the fuselage (as in an
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aerobatic plane), positive means that the leading
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edge is higher than the trailing edge (as in a
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trainer).
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twist: The difference between the incidence angle at the
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wing root and the incidence angle at the wing
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tip. Typically, this is a negative number so
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that the wing tips have a lower angle of attack
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and stall after the wing root (washout).
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taper: The taper fraction, expressed as the tip chord
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divided by the root chord. A taper of one is a
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hershey bar wing, and zero would be a wing ending
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at a point. Defaults to one.
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sweep: The sweep angle of the wing, in degrees. Zero is
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no sweep, positive angles are swept back.
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Defaults to zero.
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dihedral: The dihedral angle of the wing. Positive angles
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are upward dihedral. Defaults to zero.
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idrag: Multiplier for the "induced drag" generated by this
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surface. In general, low aspect wings will
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generate less induced drag per-AoA than high
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aspect (glider) wings. This value isn't
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constrained well by the solution process, and may
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require tuning to get throttle settings correct in
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high AoA (approach) situations.
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hstab: These defines the horizontal stabilizer of the aircraft.
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Internally, it is just awing objects and therefore work the
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same in XML. You are allowed only one hstab object; the
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solver needs to know which wing's incidence to play with to
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get the aircraft trimmed correctly.
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vstab: A "vertical" stabilizer. Like hstab, this is just another
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wing, with a few special properties. The surface is not
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"mirrored" as are wing and hstab objects. If you define a
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left wing only, you'll only get a left wing. The default
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dihedral, if unspecified, is 90 degrees instead of zero.
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But all parameters are equally settable, so there's no
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requirement that this object be "vertical" at all. You can
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use it for anything you like, such as extra wings for
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biplanes. Most importantly, these surfaces are not involved
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with the solver computation, so you can have none, or as
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many as you like.
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mstab: A mirrored horizontal stabilizer. Exactly the same as wing, but
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not involved with the solver computation, so you can have none,
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or as many as you like.
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stall: A subelement of a wing (or hstab/vstab/mstab) that specifies the
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stall behavior.
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aoa: The stall angle (maximum lift) in degrees. Note that
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this is relative to the wing, not the fuselage (since
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the wing may have a non-zero incidence angle).
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width: The "width" of the stall, in degrees. A high value
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indicates a gentle stall. Low values are viscious
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for a non-twisted wing, but are acceptable for a
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twisted one (since the whole wing will not stall at
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the same time).
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peak: The height of the lift peak, relative to the
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post-stall secondary lift peak at 45 degrees.
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Defaults to 1.5. This one is deep voodoo, and
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probably doesn't need to change much. Bug me for an
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explanation if you're curious.
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flap0, flap1, slat, spoiler:
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These are subelements of wing/hstab/vstab objects, and specify
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the location and effectiveness of the control surfaces.
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start: The positition along the wing where the control
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surface begins. Zero is the root, one is the tip.
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end: The position where the surface ends, as above.
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lift: The lift multiplier for a flap or slat at full
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extension. One is a no-op, a typical aileron might
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be 1.2 or so, a giant jetliner flap 2.0, and a
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spoiler 0.0. For spoilers, the interpretation is a
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little different -- they spoil only "prestall" lift.
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Lift due purely to "flat plate" effects isn't
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affected. For typical wings that stall at low AoA's
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essentially all lift is pre-stall and you don't have
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to care. Jet fighters tend not to have wing
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spoilers, for exactly this reason. This value is
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not applicable to slats, which affect stall AoA
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only.
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drag: The drag multiplier, as above. Typically should be
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higher than the lift multiplier for flaps.
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aoa: Applicable only to slats. This indicates the
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angle by which the stall AoA is translated by the
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slat extension.
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jet: A turbojet/fan engine. It accepts a <control> subelement to map a
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property to its throttle setting, and an <actionpt> subelement
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to place the action point of the thrust at a different
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position than the mass of the engine.
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x,y,z: The location of the engine, as a point mass.
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If no actionpt is specified, this will also
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be the point of application of thrust.
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mass: The mass of the engine, in pounds.
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thrust: The maximum sea-level thrust, in pounds.
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afterburner: Maximum additional thrust from the afterburner,
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in pounds [0].
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rotate: Vector angle of the thrust in degrees about the
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Y axis [0].
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n1-idle: Idling rotor speed [55].
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n1-max: Maximum rotor speed [102].
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n2-idle: Idling compressor speed [73].
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n2-max: Maximum compressor speed [103].
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tsfc: Thrust-specific fuel consumption [0.8].
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This should be considerably lower for modern
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turbofans.
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egt: Exhaust gas temperature at takeoff [1050].
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epr: Engine pressure ratio at takeoff [3.0].
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exhaust-speed: The maximum exhaust speed in knots [~1555].
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propeller: A propeller connected to a non-turbocharged piston engine
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The engine model is evolving, this element is likely to change
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radically in the future.
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x,y,z: The position of the mass (!) of the
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engine/propeller combination. If the point
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of force application is different (and it
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will be) it should be set with an <actionpt>
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subelement.
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mass: The mass of the engine/propeller, in pounds.
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moment: The moment, in kg-meters. This has to be
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hand calculated and guessed at for now. A
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more automated system will be forthcoming.
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Use a negative moment value for
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counter-rotating ("European" -- CCW as seen
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from behind the prop) propellers.
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radius: The radius, in meters, or the propeller.
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cruise-speed: The max efficiency cruise speed of the
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propeller. Generally not the same as the
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aircraft's cruise speed.
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cruise-rpm: The RPM of the propeller at max-eff. cruise.
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cruise-power: The power sunk by the prop at cruise, in horsepower.
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cruise-alt: The reference cruise altitude in feet.
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eng-power: Maximum BHP of the engine at sea level.
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eng-rpm: The engine RPM at which eng-power is developed
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takeoff-power: The takeoff power required by the propeller...
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takeoff-rpm: ...at the given takeoff RPM.
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displacement: The engine displacement in cubic inches.
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compression: The engine compression [??]
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turbo-mul: The turbocharger multiplier.
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wastegate-mp: The manifold pressure to activate the wastegate
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(inHG).
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min-rpm: The minimum operational RPM for a constant speed
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propeller. This is the speed to which the
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prop governor will seek when the blue lever
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is at minimum..
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max-rpm: The maximum operational RPM for a constant speed
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propeller. See above.
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gear-ratio: The factor by which the engine RPM is multiplied
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to produce the propeller RPM. Optional (defaults
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to 1.0).
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actionpt: Defines an "action point" for an enclosing jet or propeller
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element. This is the location where the force from the thruster
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will be applied.
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x,y,z: The location of force application.
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gear: Defines a landing gear. Accepts <control> subelements to map
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properties to steering and braking.
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x,y,z: The location of the fully-extended gear tip.
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compression: The distance along the Z axis that the gear
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will compress. Compression along other
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vectors is supported internally, but not in
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the XML parser. Bug me if you wantthis
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added.
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sfric: Static (non-skidding) coefficient of
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friction. Defaults to 0.8.
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dfric: Dynamic friction. Defaults to 0.7.
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retract-time: The time, in seconds, that the gear takes to
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fully retract or extend. Defaults to zero,
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which indicates a non-retractable gear.
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spring: A dimensionless multiplier for the automatically
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generated spring constant. Increase to make
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the gear stiffer, decrease to make it
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squishier.
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damp: A dimensionless multipler for the automatically
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generated damping coefficient. Decrease to
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make the gear "bouncier", increase to make it
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"slower". Beware of increasing this too far:
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very high damping forces can result and make
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the numerics unstable. If you can't make the
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gear stop bouncing with this number, try
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increasing the compression length instead.
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tank: A fuel tank. Tanks in the aircraft are identified
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numerically (starting from zero), in the order they are
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defined in the file. If the left tank is first, "tank[0]"
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will be the left tank.
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x,y,z: The location of the tank.
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capacity: The maximum contents of the tank, in pounds. Not
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gallons -- YASim supports fuels of varying
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densities.
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jet: A boolean. If present, this causes the fuel
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density to be treated as Jet-A. Otherwise,
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gasoline density is used. A more elaborate
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density setting (in pounds per gallon, for
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example) would be easy to implement. Bug me.
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ballast: This is a mechanism for modifying the mass distribution of
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the aircraft. A ballast setting specifies that a particular
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amount of the empty weight of the aircraft must be placed at
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a given location. The remaining non-ballast weight will be
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distributed "intelligently" across the fuselage and wing
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objects. Note again: this does NOT change the empty weight
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of the aircraft.
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x,y,z: The location of the ballast.
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mass: How much mass, in pounds, to put there. Note that
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this value can be negative. I find that I often need
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to "lighten" the tail of the aircraft.
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weight: This is an added weight, something not part of the empty
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weight of the aircraft, like passengers, cargo, or external
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stores. The actual value of the mass is not specified here,
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instead, a mapping to a propery is used. This allows
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external code, such as the panel, to control the weight
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(loading a given cargo configuration from preference files,
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dropping bombs at runtime, etc...)
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x,y,z: The location of the weight.
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mass-prop: The name of the fgfs property containing the
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mass, in pounds, of this weight.
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size: The aerodynamic "size", in meters, of the
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object. This is important for external stores,
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which will cause drag. For reasonably
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aerodynamic stuff like bombs, the size should be
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roughly the width of the object. For other
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stuff, you're on your own. The default is zero,
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which results in no aerodynamic force (internal
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cargo).
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solve-weight:
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Subtag of approach and cruise parameters. Used to specify a
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non-zero setting for a <weight> tag during solution. The
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default is to assume all weights are zero at the given
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performance numbers.
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idx: Index of the weight in the file (starting with zero).
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weight: Weight setting in pounds.
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control: This element, which can appear in two different contexts,
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manages a mapping from fgfs properties (user input) to
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settable values on the aircraft's objects. Note that the
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value to be set MUST (!) be valid on the given object type.
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This is not checked for by the parser, and will cause a
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runtime crash if you try it. Wing's don't have throttle
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controls, etc... Note that multiple axes may be set on the
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same value. They are summed before setting.
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One serious shortcoming of the current implementation is
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that there is no provision for modifying the values read
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from properties. There needs to be a way to scale,
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translate and truncate the values. On its way, I promise.
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axis: The name of the double-valued fgfs property "axis" to
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use as input, such as "/controls/flight/aileron".
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output: Which property to set on the objects. It can have
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the following values:
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THROTTLE - The throttle on a jet or propeller.
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MIXTURE - The mixture on a propeller.
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REHEAT - The afterburner on a jet (unimpl.).
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PROP - The propeller advance (unimpl.)
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BRAKE - The brake on a gear.
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STEER - The steering angle on a gear.
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INCIDENCE - The incidence angle of a wing.
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FLAP0 - The flap0 deflection of a wing.
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FLAP1 - The flap1 deflection of a wing.
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SLAT - The slat extension of a wing.
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SPOILER - The spoiler extension for a wing.
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CYCLICAIL - The "aileron" cyclic input of a rotor
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CYCLICELE - The "elevator" cyclic input of a rotor
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COLLECTIVE - The collective input of a rotor
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ROTORENGINEON - If not equal zero the rotor is rotating
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invert: Negate the value of the property before setting on
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the object.
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split: Applicable to wing control surfaces. Sets the
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normal value on the left wing, and a negated value
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on the right wing.
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square: Squares the value before setting. Useful for
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controls like steering that need a wide range, yet
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lots of sensitiviy in the center. Obviously only
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applicable to values that have a range of [-1:1] or
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[0:1].
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A control element can also appear inside of an <approach> or
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<cruise> element. Here, it specifies a particular value of an
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axis mapping that should be true under the given
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conditions. At cruise, the throttle is generally at a high
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setting, the flaps and slats are up During approach
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the flaps and slats are down, etc...
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axis: As above, the name of the input property.
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value: A floating point number that the property is expected
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to hold.
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rotor: A rotor. Used for simulating helicopters. You can have one, two
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or even more.
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If you specify a rotor, you do not need to specify a wing or hstab,
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the settings for approach and cruise will be ignored then. Instead
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stored results from the c182 will be used.
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name: The name of the rotor.
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(some data is stored at /rotors/name/)
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The rpm, cone angle, yaw angle and roll angle are stored
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for the complete rotor. For every blade the position
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angle, the flap angle and the incidence angle are stored.
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All angles are in degree, positive values always mean "up".
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This is not completely tested, but seem to work at least
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for rotors rotating counterclockwise.
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x,y,z: The position of the rotor center
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nx,ny,nz: The normal of the rotor (pointing upwards, will be
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normalized by the computer)
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fx,fy,fz: A Vector pointing forward, if not perpendicular to the
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normal it will be corrected by the computer
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diameter: The diameter in meter
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numblades: The number of blades
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weightperblade: The weight per blade in pounds
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relbladecenter: The relative center of gravity of the blade. Maybe
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not 100% correct interpreted; use 0.5 for the start and
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change in small steps
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rpm: rounds per minute.
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ccw: determines if the rotor rotates clockwise (="false") or
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counterclockwise (="true"), (if you look on the top of the
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normal, so the bo105 has counterclockwise rotor)
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maxcollective: The maximum of the collective incidence in degree
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mincollective: The minimum of the collective incidence in degree
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maxcyclicele: The maximum of the cyclic incidence in degree for
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the elevator like function
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mincyclicele: The minimum of the cyclic incidence in degree for
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the elevator like function
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maxcyclicail: The maximum of the cyclic incidence in degree for
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the aileron like function
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mincyclicail: The minimum of the cyclic incidence in degree for
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the aileron like function
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pitch_a: A collective incidence angle, used for the next token
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forceatpitch_a: The force, the rotor is producing when the incident
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angle is equal pitch_a. I.e. hover-pitch and a force
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equivalent to the weight. (in pounds of force)
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pitch_b: A collective incidence angle, used for the next token
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poweratpitch_b: the power the rotor needs at pitch_b. (i.e. at the
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bo105 the main rotor consumes bout 90% of the engine power,
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and 9% the tail rotor. In kW. Used for calculation of the
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torque.
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poweratpitch_0: the power the rotor needs at zero pitch.
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In kW. Used for calculation of the torque.
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notorque: If set to "true" the calculated torque is always zero.
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Very helpful while adjusting rotor parameters.
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flapmin: Minimum flapping angle. (Should normally never reached)
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flapmax: Maximum flapping angle. (Should normally never reached)
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flap0: Flapping angle at no rotation, i.e. -5
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dynamic: this changes the reactions peed of the rotor to an input.
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normally 1 (Maybe there are rotors with a little faster
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reaction, than use a value a little greater than one.
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A value greater than one will result in a more inert,
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system. Maybe it's useful for simulating the rotor of the
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Bell UH1
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rellenflaphinge: The relative length from the center of the rotor
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to the flapping hinge. Can be taken from pictures of the
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helicopter (i.e. 0 for Bell206, about 0.05 for most
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rotors) For rotors without flapping hinge (where the blade
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are twisted instead, i.e. Bo 105, Lynx) use a mean value,
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maybe 0.2. This value has a extreme result in the behavior
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of the rotor
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delta3: Some rotors have a delta3 effect, which results in a
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decreasing of the incidence when the rotor is flapping.
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A value of 0 (as most helicopters have) means no change in
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incidence, a value of 1 result in a decreases of one degree
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per one degree flapping.
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So delta3 is the proportional factor between flapping and
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decrease of incidence. I.e. the tail rotor of a Bo105 has
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a delta3 of 1.
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delta: A factor for the damping constant for the flapping. 1 means
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a analytical result, which is only a approximation. Has a
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very strong result in the reaction of the rotor system on
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control inputs.
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If you know the flapping angle for a given cyclic input you
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can adjust this by changing this value. Or if you now the
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maximum roll rate or ...
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translift: Helicopters have "translational lift", which is due to
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turbulence and hard to calculate, so this simulation uses
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a phenomenological ansatz. Use .1 for the start value
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dragfactor: The drag of the rotating rotor perpendicular to the
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rotor plane is larger than the drag of the not rotating
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rotor. Hard to calculate, so it is added phenomenological
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Any rotor needs a <control> subelement for the engine
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(ROTORENGINEON) and can have <control> subelements for the cyclic
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(CYCLICELE, CYCLICAIL) and collective (COLLECTIVE) input.
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The rotor simulation is very "beta" and not finished yet. So don't
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spend too much time to adjust a flight behavior to the smallest
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details now.
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