<?xml version="1.0"?> <!-- ************************************************************************ YASim aerodynamic model for a Piper J3 Cub. Started 2002-08-15 by David Megginson. This aerodynamic model is based on three-views, unauthoritative performance data, and wild guesses. These sites provided particularly useful information or were simply fun to visit: Performance data: http://www.marss.com/cub.htm Weight and balance: http://www.danford.net/balance.htm Three-view: http://www.fiddlersgreen.net/aircraft/private/j3cub/j3cub_info/j3_info.htm Useless but fun free paper model: http://www.fiddlersgreen.net/aircraft/private/j3cub/j3cub.htm Useless but fun 1945 Piper Cub add from FLYING: http://www.fiddlersgreen.net/aircraft/private/j3cub/j3cub_info/piperad.jpg The reference datum for measurements is the leading edge of the wing, since it is what the weight-and-balance site above uses. ************************************************************************ --> <!-- 680lb empty weight. --> <!-- FIXME: this includes the engine; is that correct? --> <airplane mass="680"> <!-- Approach configuration (actually touchdown, I think) --> <approach speed="25" aoa="16"> <control-setting axis="/controls/throttle[0]" value="0.3"/> <control-setting axis="/controls/mixture[0]" value="1.0"/> </approach> <!-- Cruise configuration --> <cruise speed="67" alt="0"> <control-setting axis="/controls/throttle[0]" value="1.0"/> <control-setting axis="/controls/mixture[0]" value="1.0"/> </cruise> <!-- pilot's eyepoint --> <cockpit x="-0.23" y="0" z="-0.30"/> <fuselage ax="1.37" ay="0" az="-0.71" bx="-4.81" by="0" bz="-0.65" width="0.71" taper="0.16" midpoint="0.17"/> <!-- I treat it as a perfectly rectangular wing for now. Note that the dihedral is exaggerated to simulate hull-interference effects on a high-wing aircraft; once YASim models that properly, the angle should be reduced to something like 2 degrees. Note that the J3 Cub has no flaps. With a stall speed of 25kt, who needs them? From what I've read, the ailerons add lots of drag. --> <wing x="-0.80" y="0.42" z="0.0" taper="1.0" length="4.87" chord="1.60" sweep="0" dihedral="5" camber="0.1"> <stall aoa="16" width="6" peak="1.5"/> <flap0 start=".31" end="0.85" lift="1.5" drag="1.4"/> <control-input axis="/controls/aileron" control="FLAP0" split="true"/> <control-input axis="/controls/aileron-trim" control="FLAP0" split="true"/> <control-output control="FLAP0" side="left" prop="/surface-positions/left-aileron-pos-norm"/> <control-output control="FLAP0" side="right" prop="/surface-positions/right-aileron-pos-norm"/> </wing> <!-- FIXME: taper (used the C172 value) --> <hstab x="-4.87" y="0.05" z="-0.42" taper="0.5" effectiveness="1.24" length="1.49" chord="1.13" sweep="0"> <stall aoa="16" width="4" peak="1.5"/> <flap0 start="0" end="1" lift="1.7" drag="1.2"/> <control-input axis="/controls/elevator" control="FLAP0"/> <control-input axis="/controls/elevator-trim" control="FLAP0"/> <control-output control="FLAP0" prop="/surface-positions/elevator-pos-norm"/> </hstab> <!-- FIXME: taper (used the C172 value) --> <!-- rudder has to be able to counteract aileron drag --> <vstab x="-4.87" y="0" z="-0.65" taper="0.38" effectiveness="1.24" length="1.31" chord="1.37" sweep="0"> <stall aoa="16" width="4" peak="1.5"/> <flap0 start="0" end="1" lift="1.5" drag="1.2" effectiveness="1.5"/> <control-input axis="/controls/rudder" control="FLAP0" invert="true"/> <control-input axis="/controls/rudder-trim" control="FLAP0" invert="true"/> <control-output control="FLAP0" prop="/surface-positions/rudder-pos-norm" min="1" max="-1"/> </vstab> <!-- FIXME: engine mass (just a guess; it's a small engine) --> <!-- Assume 75% power at 8000ft --> <propeller radius="0.95" cruise-speed="60" cruise-rpm="2300" cruise-alt="8000" cruise-power="48" takeoff-power="55" takeoff-rpm="2300" eng-power="65" eng-rpm="2700" x="0.71" y="0" z="-0.65" mass="150" moment="8"> <actionpt x="1.31" y="0" z="-0.65"/> <control-input axis="/controls/throttle[0]" control="THROTTLE"/> <control-input axis="/controls/starter[0]" control="STARTER"/> <control-input axis="/controls/magnetos[0]" control="MAGNETOS"/> <control-input axis="/controls/mixture[0]" control="MIXTURE"/> </propeller> <!-- FIXME: the J3 Cub may not actually have a tail-wheel lock --> <gear x="-5.17" y="0" z="-0.71" compression="0.2"> <control-input axis="/controls/tailwheel-castering" control="CASTERING"/> </gear> <gear x="0" y="0.95" z="-1.96" compression=".1"> <!-- left main --> <control-input axis="/controls/brakes[0]" control="BRAKE" split="true"/> <control-input axis="/controls/parking-brake" control="BRAKE" split="true"/> </gear> <gear x="0" y="-0.95" z="-1.96" compression=".1"> <!-- right main --> <control-input axis="/controls/brakes[1]" control="BRAKE" split="true"/> <control-input axis="/controls/parking-brake" control="BRAKE" split="true"/> </gear> <!-- There's just one 12-gallon tank, right behind the engine (!!!) --> <tank x="-0.45" y="0" z="-0.89" capacity="72"/> <!-- Note the tandem seating; the x values (arms) come from the weight-and-balance page cited at the start. --> <!-- pilot --> <weight x="-0.23" y="0" z="-0.70" mass-prop="/yasim/j3cub/pilot-lb"/> <!-- passenger --> <weight x="-0.91" y="0" z="-0.70" mass-prop="/yasim/j3cub/passenger-lb"/> </airplane>