Optica/Optica-yasim.xml

<?xml version="1.0"?>
<!--

YASim Aerodynamic Model for the OA-7 Optica
Gary Neely aka 'Buckaroo'
Optica FDM version 3

V speeds:

Vr	50 kts (takeoff at 10 deg flaps)
V2	55 kts
Vs	42 kts
Vs0	38 kts
Vno	115
VA	113
Vne	140 kts
Vfe	1-10 deg, 110 kts
	11-50 deg, 85 kts

Ceiling	13,000'


Weight and Balance:

empty				2058
max takeoff and landing		2900 lbs
max zero fuel			2734 lbs
max load			512 lbs (people+baggage)
min load			170 lbs (seated pilot)
max baggage tray load		66 lbs

CG Range (datum is wing leading edge LE):
forward limit	20% MAC, 10.4" aft of datum for all weights
aft limit	32% MAC, 16.6" aft of datum at 2400 lbs
		30% MAC, 15.6" aft of datum at 2900 lbs

chord		1.369	1/2=0.685
		x-axis:
wing loc	3.240
LE		2.555
20% MAC		2.829
25% MAC		2.900
30% MAC		2.966
32% MAC		2.993
solved CG	2.917	@2700lbs


Fuel:
Two tanks at 33 gallons each, 0.8 gallons unusable in each
Fuel is drawn from a selectable tank, both may not be an option

Control Surface Limits:
		Up/Down
Flaps		-/50
Ailerons	22/12
Elevator	26.5/19
Elevator Trim	20/28
Rudders		25L/25R

Engine (from type cert sheet):
Avco Lycoming IO-540-V4A5D
max power	2700 RPM, 260 C (500 F) CHT, 260 HP
max continuous	2200 RPM, 220 C CHT
max oil press	95 psi
		115 psi (starting, warm-up)
min oil press	55 psi (normal), 25 psi (idling)
fuel press	(-2)-35 psi (at engine pump inlet)
		12-45 psi (at injector inlet)
max EGT		850 C
max oil temp	118 C
min oil temp	60 C (continuous)
bore 		5.125
stroke		4.375
disp		541.5
comp		8.7:1
weight		383 (dry)
oil max		8 gallons
oil norm	6 gallons

Prop:
Hoffman HO E315
5 blades, fixed pitch
diameter	47.71", 1.212m(0.606m R)
max RPM		2700
rotation	CW from rear
weight		37.4 lbs, 17 kg
moment		6.76, calculated using mean of rod and disk methods
		rod (mR^2)/3 * blades = 17*0.367/3*5 = 10.4
		disk (mR^2)/2 = 17*0.367/2 = 3.12

YASim solution notes:

Solution results:       Iterations: 954
 Drag Coefficient: 20.811853
       Lift Ratio: 126.860756
       Cruise AoA: -4.067267
   Tail Incidence: -0.271942
Approach Elevator: -0.839581
               CG: x:-2.917, y:0.000, z:0.164

  Inertia tensor : 3259.927, -0.000, 645.507
        [kg*m^2]   -0.000, 4609.323, 0.000
     Origo at CG   645.507, 0.000, 7608.934
-->


<airplane mass="2058">

<!--
Approach AoA is a guess, giving something around half the wing's critical AoA. In reality, with full or near-full flaps it's probably significantly more shallow than this. (See wing notes below.)
I don't really know what the top speed of the Optica is with the IO-540; the original Optica used a 150 HP engine giving anemic performance. Production models used 260 or 300 HP engines. The plane was meant for slow and efficient cruise speeds but I know from one flight test report that it could be pushed to Vne. Therefore I use Vne as the top-end.
-->
<approach speed="42" aoa="8" fuel="0.2">
  <control-setting axis="/controls/engines/engine[0]/throttle-fdm" value="0.4"/>
  <control-setting axis="/controls/engines/engine[0]/mixture" value="1.0"/>
  <control-setting axis="/controls/flight/flaps" value="1.0"/>
  <control-setting axis="/controls/flight/flaps-fixed" value="0.2"/>
  <solve-weight idx="0" weight="250"/>
  <solve-weight idx="1" weight="0"/>
  <solve-weight idx="2" weight="0"/>
</approach>

<cruise speed="140" alt="5000" fuel="0.6">
  <control-setting axis="/controls/engines/engine[0]/throttle-fdm" value="1.0"/>
  <control-setting axis="/controls/engines/engine[0]/mixture" value="0.74"/>
  <control-setting axis="/controls/flight/flaps" value="0"/>
  <control-setting axis="/controls/flight/flaps-fixed" value="0.2"/>
  <control-setting axis="/controls/flight/elevator-trim" value="0.16"/>
  <solve-weight idx="0" weight="250"/>
  <solve-weight idx="1" weight="0"/>
  <solve-weight idx="2" weight="0"/>
</cruise>


<cockpit x="-1.5" y="0" z="0.2"/>


<!--
Cabin, an approximation for a duct body for drag, and two booms. Duct width is based on the duct as a torus, using an area based on that of a circle of the outer diameter minus a circle of the inner diameter, and calculating an effective diameter (0.73) based on the result. It's likely a bad guesstimation and its moment will be too small, but better than nothing.
-->
<fuselage ax="0" ay="0" az="-0.03" bx="-5.09" by="0" bz="0.04" width="1.6" taper=".4" midpoint="0.25"/>

<fuselage ax="-2.5" ay="0" az="0.05" bx="-4.3" by="0" bz="0.05" width="0.73" taper="0.2" midpoint="0.5"/>

<fuselage ax="-2.72" ay="1.69" az="-0.01" bx="-7.16" by="1.69" bz="0.32" width="0.31" taper="0.5" midpoint="0.15"/>
<fuselage ax="-2.72" ay="-1.69" az="-0.01" bx="-7.16" by="-1.69" bz="0.32" width="0.31" taper="0.5" midpoint="0.15"/>


<!--
Wing:
I have no numbers for incidence, so I'm using 0. Given the already good view forward, it probably wouldn't need much if any incidence. Also, since the airfoil has such a high lift factor, fast cruise has a significant nose-down attitude which would be exaggerated by incidence.
I have no numbers for twist, so using a generic -3 degrees.
The model uses an older wingtip design. Later versions appear to use a modified Horner tip, which I may re-model in the future. The tips might give a few more inches of effective span due to lateral vortex displacement etc., but I currently don't account for that.
Flaps over 10 deg serve to increase the Optica's angle of descent, ie, bring the nose down for approach. Total full-flap pitch-down should be about 11 degrees from 10 deg flaps to 50 deg flaps. It's difficult to achieve this because YASim does not allow positioning the effects of flap lift/drag or modifying Cm. With no flaps, the sink-rate at 70 kts should be 500 ft/min. With full flaps, this becomes 900 ft/min. Flap drag was set to get something like these numbers, but the FDM has been through many changes since I last flight tested for sink rate so I'm not sure how it fares now.
The airfoil is a GA(W)-1 meant for low-speed, high-lift applications, with a Cl at 0 alpha of about 0.4, 0 Cl at -4.5 alpha, and a Clmax of about 1.6, giving a YASim camber of ~0.25. Max lift occurs at about 16 degrees. Stall should be very gentle and mushy with little tendency to drop a wing, so I set a fairly wide width.
-->
<wing x="-3.235" y="1.866" z="0.06" taper="1" length="4.074" chord="1.369" sweep="0" dihedral="3" incidence="0" camber="0.25" twist="-3.0">
  <stall aoa="16" width="10" peak="1.5"/>
  <flap0 start="0" end="0.5" lift="1.6" drag="1.75"/>
  <flap1 start="0.5" end="1.0" lift="1.2" drag="1.2"/>
  <control-input axis="/controls/flight/flaps" control="FLAP0"/>
  <control-input axis="/controls/flight/aileron" control="FLAP1" split="true"/>
  <control-input axis="/controls/flight/aileron-trim" control="FLAP1" split="true"/>
  <control-output control="FLAP0" prop="/surface-positions/flap-pos-norm"/>
  <control-output control="FLAP1" side="left" prop="/surface-positions/left-aileron-pos-norm"/>
  <control-output control="FLAP1" side="right" prop="/surface-positions/right-aileron-pos-norm"/>
  <control-speed control="FLAP0" transition-time="10"/>
</wing>

<!--
Wing section inboard of booms. Inboard flaps are fixed at 10 degrees. As this section is optimized for lift, I have substantially reduced the drag component of 'flaps'.
-->
<mstab x="-3.341" y="0.84" z="0.06" taper="1" length="1.043" chord="1.583" sweep="0" dihedral="0" incidence="0" camber="0.25" twist="0">
  <stall aoa="16" width="10" peak="1.5"/>
  <flap0 start="0" end="1" lift="1.6" drag="1.2"/>
  <control-input axis="/controls/flight/flaps-fixed" control="FLAP0"/>
  <control-speed control="FLAP0" transition-time="5"/>
</mstab>


<!--
Nothing fancy here. Camber adjusted to help achieve a reasonable tail incidence. Elevator lift is heavier than I would usually advocate, but since the payload is far forward compared to the CG it needs a strong positive response for the variety of loads.
-->
<hstab x="-7.361" y="0" z="1.453" taper="1" length="1.161" chord="1.153" sweep="0" camber="0.05">
  <stall aoa="18" width="4" peak="1.5"/>
  <flap0 start="0" end="1" lift="1.83" drag="1.3"/>
  <control-input axis="/controls/flight/elevator" control="FLAP0"/>
  <control-input axis="/controls/flight/elevator-trim" control="FLAP0"/>
  <control-output control="FLAP0" prop="/surface-positions/elevator-pos-norm"/>
</hstab>


<!--
Lift values adjusted to give a reasonable slip ability, but may need more tuning.
The model currently uses the older design with no vstab root extensions.
-->
<vstab x="-7.3" y="1.68" z="0.133" taper="0.73" length="1.257" chord="1.587" sweep="3" dihedral="109">
  <stall aoa="16" width="4" peak="1.5"/>
  <flap0 start="0" end="1" lift="1.35" drag="1.3"/>
  <control-input axis="/controls/flight/rudder" control="FLAP0" invert="true"/>
  <control-input axis="/controls/flight/rudder-trim" control="FLAP0" invert="true"/>
  <control-output control="FLAP0" prop="/surface-positions/rudder-pos-norm" min="1" max="-1"/>
</vstab>
<vstab x="-7.3" y="-1.68" z="0.133" taper="0.73" length="1.257" chord="1.587" sweep="3" dihedral="71">
  <stall aoa="16" width="4" peak="1.5"/>
  <flap0 start="0" end="1" lift="1.35" drag="1.3"/>
  <control-input axis="/controls/flight/rudder" control="FLAP0" invert="true"/>
  <control-input axis="/controls/flight/rudder-trim" control="FLAP0" invert="true"/>
  <control-output control="FLAP0" prop="/surface-positions/rudder-pos-norm" min="1" max="-1"/>
</vstab>


<!--
Mass assuming engine dry weight + prop weight + 42 lbs of oil (6 gals at 7 lbs).
Cruise speed is adjusted for reasonable performance.
Thrust direction gives a slight upthrust vector (3 deg) due to downcurved trailing edge of duct.
-->
<propeller x="-2.40" y="0" z="0.0"
	radius="0.606"
	mass="462.4"
	moment="6.76"
	cruise-power="156"
	cruise-rpm="1900"
	cruise-speed="130"
	cruise-alt="5000"
	takeoff-power="260"
	takeoff-rpm="2700">
  <piston-engine
	eng-rpm="2700"
	eng-power="260"
	alt="0"
	displacement="541.5"
	compression="8.7"/>
  <actionpt x="-3.6" y="0" z="0.04"/>
  <dir x="0.9986" y="0.0" z="0.05234" />
  <control-input axis="/controls/engines/engine[0]/throttle-fdm" control="THROTTLE"/>
  <control-input axis="/controls/engines/engine[0]/starter" control="STARTER"/>
  <control-input axis="/controls/engines/engine[0]/magnetos" control="MAGNETOS"/>
  <control-input axis="/controls/engines/engine[0]/mixture" control="MIXTURE"/>
</propeller>


<!--
Conventional trike arrangement with the nose wheel offset slightly.
-->
<gear x="-0.73" y="0.2" z="-1.19"
	compression="0.1"
	dfric="0.3"
	sfric="0.5">
  <control-input axis="/controls/flight/rudder" control="STEER"
	src0="-1.0" src1="1.0"
	dst0="-0.1" dst1="0.1"/>
</gear>

<gear x="-3.38" y="1.70" z="-1.14"
	compression="0.2"
	dfric="0.6"
	sfric="0.7">
  <control-input axis="/controls/gear/brake-left" control="BRAKE" split="true"/>
  <control-input axis="/controls/gear/brake-parking" control="BRAKE" split="true"/>
</gear>

<gear x="-3.38" y="-1.70" z="-1.14"
	compression="0.2"
	dfric="0.6"
	sfric="0.7">
  <control-input axis="/controls/gear/brake-right" control="BRAKE" split="true"/>
  <control-input axis="/controls/gear/brake-parking" control="BRAKE" split="true"/>
</gear>


<!--
Fuel tanks are located in the outboard wings forward of the main spar and laterally
positioned ahead of the flaps.
-->
<tank x="-2.68" y="2.88"  z="0.12" capacity="198"/>
<tank x="-2.68" y="-2.88" z="0.12" capacity="198"/>


<!--
The real Optica is very sensitive to weight and balance. Single-pilot operation requires significant ballast in the nose. In many photos there appears to be a rack of weights fitted just forward of the instrumentation pylon. The tailbooms contain an adjustable sliding weight that can fine-tune balance on the ground. This should be reflected by a change in ballast position, but currently YASim doesn't support property-driven ballast, so I'm using a weight.
-->
<ballast x="-1" y="0" z="0" mass="375"/>

<weight x="-1"   y="0" z="0" mass-prop="/sim/weight[0]/weight-lb"/>	<!-- crew -->
<weight x="-0.2" y="0" z="0" mass-prop="/sim/weight[1]/weight-lb"/>	<!-- nose weights -->
<weight x="-7"   y="0" z="0" mass-prop="/sim/weight[2]/weight-lb"/>	<!-- tail sliding balance weight -->


</airplane>