2003-05-07 01:52:04 +00:00
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<?xml version="1.0"?>
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<!--
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************************************************************************
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YASim aerodynamic model for a P-51D mustang
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Started 2003-04-24 by Jim Wilson
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This aerodynamic model is based on three-views, unauthoritative
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performance data, and wild guesses. These sites provided particularly
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useful information or were simply fun to visit:
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Performance data:
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http://www.hq.nasa.gov/office/pao/History/SP-468/app-a2.htm
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http://www.olympicflightmuseum.com/aircraft_gallery/p51d_mustang.htm
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http://www.btinternet.com/~lee_mail/P51.html
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http://www.sprucegoose.org/pdfs/planes/P51Mustang.pdf
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Weight and balance:
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http://www.p51.wjackparker.com/P51_Additional_reference_material/x_maintenance.htm
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http://www.nzfpm.co.nz/aircraft/p51d.htm
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http://www.wpafb.af.mil/museum/engines/eng33.htm
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Three-view:
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http://members.optushome.com.au/gjmustang/docs/3-View.html
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(Note: I have local copies if this url becomes un-available)
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The reference datum for measurements is the nose.
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************************************************************************
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-->
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<!-- Weight of everything but fuel (7010 empty) -->
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2003-05-07 02:01:42 +00:00
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<airplane mass="7190">
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2003-05-07 01:52:04 +00:00
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<!-- Approach configuration -->
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Andy Ross's changes:
Changes:
Fit the solver to the known stall speed instead of an abstract
approach configuration. That is, specify stall AoA and speed as
"approach" values. At approach weight (20% fuel) I can now just
barely hold the aircraft in the air without losing it at 87 kias.
Note that the IAS guage seems to have a slight calibration error, it
was reading something that looked more like 95 knots; I got the real
value out of the property browser.
Change the sign of the incidence value for the wing. It specifies a
rotation about the axis pointing out the left wing, so positive values
are "nose down".
Increase the "effectiveness" of the tail surfaces quite a bit.
Smaller surfaces do actually need higher values. YASim scales surface
force coefficients with their areas, which is correct within a single
wing. But between wing-like devides, generated forces kinda/sorta
scale linearly with their spans. This is particularly important for
tail draggers, since YASim's lack of prop wash modelling needs to be
offset by extra elevator authority.
Add a camber value to the wing. Most wing airfoils are asymmetric,
and produce non-zero lift at zero AoA. I picked 0.1 (10% of stall
lift at zero alpha) as a reasonable guess. If someone has airfoil
data for the Mustang we could look this up exactly. This was the
biggest change, which allows the cruise AoA to be much lower than
approach or stall.
Reduced the compression value for the tail wheel to 20cm. These
things are very stiff; they "compress" only as much as the tires do.
Even 0.2 is too much motion, but the numerics tend to go wacky when
you give them very high spring coefficients. This helped the ground
handling a little bit.
Removed the extra damping from the main gear. My impression of tail
draggers is that they tend to have "squishy" main gear. Again, this
(subjectively) seemed to improve ground handling to me. I also tried
reducing the spring constants to 0.5, but that ended up being too
squishy -- you could see the ship (stopped on the ground) bank to the
left by 2-3° when you pushed the throttle forward.
Ground handling is still pretty difficult; I get the best results by
holding the tail down until 90 knots or so and then very gently
lowering the stick. The aircraft bobs once or twice and then lifts
off. I don't think this is proper procedure, though.
Andy
2003-05-07 01:53:39 +00:00
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<approach speed="87" aoa="13">
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<control-setting axis="/controls/engines/engine[0]/throttle" value="0.2"/>
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2003-05-07 01:52:04 +00:00
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<control-setting axis="/controls/engines/engine[0]/mixture" value="1.0"/>
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<control-setting axis="/controls/engines/engine[0]/propeller-pitch" value="0.5"/>
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<control-setting axis="/controls/flight/flaps" value="1.0"/>
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<control-setting axis="/controls/gear/gear-down" value="1"/>
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</approach>
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<!-- Cruise configuration -->
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<!-- 350 mph, 304 knots -->
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2003-05-07 02:01:42 +00:00
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<cruise speed="380" alt="25000">
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2003-05-07 01:52:04 +00:00
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<control-setting axis="/controls/engines/engine[0]/throttle" value="1.00"/>
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<control-setting axis="/controls/engines/engine[0]/mixture" value="1.00"/>
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2003-05-07 02:01:42 +00:00
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<control-setting axis="/controls/engines/engine[0]/propeller-pitch" value="0.8"/>
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2003-05-07 01:52:04 +00:00
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<control-setting axis="/controls/engines/engine[0]/boost" value="1.0"/>
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<control-setting axis="/controls/flight/flaps" value="0.0"/>
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<control-setting axis="/controls/gear/gear-down" value="0"/>
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</cruise>
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<!-- pilot's eyepoint -->
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<cockpit x="-4.495" y="0" z="0.689"/>
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<fuselage ax="0.0" ay="0.0" az="0.0" bx="-9.9" by="0.0" bz="0.0"
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2003-05-12 15:28:03 +00:00
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width="0.94" taper="0.38"/>
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2003-05-07 01:52:04 +00:00
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<!--
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stall aoa not available
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flap drag not available
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-->
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2003-05-12 15:28:03 +00:00
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<wing x="-3.96" y="0.55" z="-0.60" taper="0.466" incidence="0"
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length="5.16" chord="2.845" sweep="-3.5" dihedral="5" camber="0.1">
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2003-05-07 01:52:04 +00:00
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<stall aoa="14" width="4" peak="1.5"/>
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2003-05-12 15:28:03 +00:00
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<flap0 start="0.024" end="0.543" lift="1.2" drag="1.8"/>
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<flap1 start="0.543" end="0.97" lift="1.3" drag="1.4"/>
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2003-05-07 01:52:04 +00:00
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<control-input axis="/controls/flight/flaps" control="FLAP0"/>
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<control-output control="FLAP0" prop="/surface-positions/flap-pos-norm"/>
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<control-speed control="FLAP0" transition-time="5"/>
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<control-input axis="/controls/flight/aileron" control="FLAP1" split="true"/>
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<control-input axis="/controls/flight/aileron-trim" control="FLAP1" split="true"/>
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</wing>
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2003-05-12 15:28:03 +00:00
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<hstab x="-8.62" y="0.18" z="0.34" taper="0.639" effectiveness="3.5"
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2003-05-07 01:52:04 +00:00
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length="1.834" chord="1.256" sweep="0" incidence="2">
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<stall aoa="15" width="4" peak="1.5"/>
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Andy Ross's changes:
Changes:
Fit the solver to the known stall speed instead of an abstract
approach configuration. That is, specify stall AoA and speed as
"approach" values. At approach weight (20% fuel) I can now just
barely hold the aircraft in the air without losing it at 87 kias.
Note that the IAS guage seems to have a slight calibration error, it
was reading something that looked more like 95 knots; I got the real
value out of the property browser.
Change the sign of the incidence value for the wing. It specifies a
rotation about the axis pointing out the left wing, so positive values
are "nose down".
Increase the "effectiveness" of the tail surfaces quite a bit.
Smaller surfaces do actually need higher values. YASim scales surface
force coefficients with their areas, which is correct within a single
wing. But between wing-like devides, generated forces kinda/sorta
scale linearly with their spans. This is particularly important for
tail draggers, since YASim's lack of prop wash modelling needs to be
offset by extra elevator authority.
Add a camber value to the wing. Most wing airfoils are asymmetric,
and produce non-zero lift at zero AoA. I picked 0.1 (10% of stall
lift at zero alpha) as a reasonable guess. If someone has airfoil
data for the Mustang we could look this up exactly. This was the
biggest change, which allows the cruise AoA to be much lower than
approach or stall.
Reduced the compression value for the tail wheel to 20cm. These
things are very stiff; they "compress" only as much as the tires do.
Even 0.2 is too much motion, but the numerics tend to go wacky when
you give them very high spring coefficients. This helped the ground
handling a little bit.
Removed the extra damping from the main gear. My impression of tail
draggers is that they tend to have "squishy" main gear. Again, this
(subjectively) seemed to improve ground handling to me. I also tried
reducing the spring constants to 0.5, but that ended up being too
squishy -- you could see the ship (stopped on the ground) bank to the
left by 2-3° when you pushed the throttle forward.
Ground handling is still pretty difficult; I get the best results by
holding the tail down until 90 knots or so and then very gently
lowering the stick. The aircraft bobs once or twice and then lifts
off. I don't think this is proper procedure, though.
Andy
2003-05-07 01:53:39 +00:00
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<flap0 start="0.0" end="1.8" lift="1.65" drag="1.2"/>
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2003-05-07 01:52:04 +00:00
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<control-input axis="/controls/flight/elevator" control="FLAP0"/>
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<control-input axis="/controls/flight/elevator-trim" control="FLAP0"/>
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<control-output control="FLAP0" prop="/surface-positions/elevator-pos-norm"/>
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</hstab>
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<!-- rudder has to be able to counteract aileron drag -->
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2003-05-07 02:01:42 +00:00
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<vstab x="-9.30" y="0" z="-0.37" taper="0.432" effectiveness="3.5"
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2003-05-12 15:28:03 +00:00
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length="1.971" chord="2.65" sweep="25" incidence="-0.62">
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2003-05-07 01:52:04 +00:00
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<stall aoa="15" width="4" peak="1.5"/>
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<flap0 start="0" end="1" lift="1.3" drag="1.2"/>
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2003-05-12 15:28:03 +00:00
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<control-input axis="/controls/flight/rudder" square="true" control="FLAP0" invert="true"/>
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2003-05-07 01:52:04 +00:00
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<control-input axis="/controls/flight/rudder-trim" control="FLAP0" invert="true"/>
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<control-output control="FLAP0" prop="/surface-positions/rudder-pos-norm"
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min="1" max="-1"/>
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</vstab>
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<propeller x="-0.75" y="0" z="0"
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radius="1.75"
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mass="1690" moment="110"
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eng-power="1490" eng-rpm="2300"
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2003-05-16 18:26:33 +00:00
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turbo-mul="2.5" wastegate-mp="30"
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2003-05-07 01:52:04 +00:00
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cruise-alt="25000" cruise-power="1350"
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2003-05-12 15:28:03 +00:00
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cruise-speed="380" cruise-rpm="2900"
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2003-05-16 18:26:33 +00:00
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manual-pitch="true" >
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2003-05-07 01:52:04 +00:00
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<actionpt x="-1.25" y="0" z="0"/>
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<control-input axis="/controls/engines/engine[0]/throttle" control="THROTTLE"/>
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<control-input axis="/controls/engines/engine[0]/starter" control="STARTER"/>
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<control-input axis="/controls/engines/engine[0]/magnetos" control="MAGNETOS"/>
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<control-input axis="/controls/engines/engine[0]/mixture" control="MIXTURE"/>
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2003-05-16 18:26:33 +00:00
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<control-input axis="/controls/engines/engine[0]/propeller-pitch" control="PROPPITCH"
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src0="0" src1="1" dst0="0.40" dst1="0.80"/>
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2003-05-07 01:52:04 +00:00
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<control-input axis="/controls/engines/engine[0]/boost" control="BOOST"/>
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</propeller>
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Andy Ross's changes:
Changes:
Fit the solver to the known stall speed instead of an abstract
approach configuration. That is, specify stall AoA and speed as
"approach" values. At approach weight (20% fuel) I can now just
barely hold the aircraft in the air without losing it at 87 kias.
Note that the IAS guage seems to have a slight calibration error, it
was reading something that looked more like 95 knots; I got the real
value out of the property browser.
Change the sign of the incidence value for the wing. It specifies a
rotation about the axis pointing out the left wing, so positive values
are "nose down".
Increase the "effectiveness" of the tail surfaces quite a bit.
Smaller surfaces do actually need higher values. YASim scales surface
force coefficients with their areas, which is correct within a single
wing. But between wing-like devides, generated forces kinda/sorta
scale linearly with their spans. This is particularly important for
tail draggers, since YASim's lack of prop wash modelling needs to be
offset by extra elevator authority.
Add a camber value to the wing. Most wing airfoils are asymmetric,
and produce non-zero lift at zero AoA. I picked 0.1 (10% of stall
lift at zero alpha) as a reasonable guess. If someone has airfoil
data for the Mustang we could look this up exactly. This was the
biggest change, which allows the cruise AoA to be much lower than
approach or stall.
Reduced the compression value for the tail wheel to 20cm. These
things are very stiff; they "compress" only as much as the tires do.
Even 0.2 is too much motion, but the numerics tend to go wacky when
you give them very high spring coefficients. This helped the ground
handling a little bit.
Removed the extra damping from the main gear. My impression of tail
draggers is that they tend to have "squishy" main gear. Again, this
(subjectively) seemed to improve ground handling to me. I also tried
reducing the spring constants to 0.5, but that ended up being too
squishy -- you could see the ship (stopped on the ground) bank to the
left by 2-3° when you pushed the throttle forward.
Ground handling is still pretty difficult; I get the best results by
holding the tail down until 90 knots or so and then very gently
lowering the stick. The aircraft bobs once or twice and then lifts
off. I don't think this is proper procedure, though.
Andy
2003-05-07 01:53:39 +00:00
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<!-- Tail wheel -->
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2003-05-16 18:26:33 +00:00
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<gear x="-7.90" y="0" z="-0.96" compression="0.2" castering="true">
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2003-05-07 01:52:04 +00:00
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</gear>
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<!-- left main -->
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2003-05-16 18:26:33 +00:00
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<gear x="-2.79" y="1.81" z="-2.20" compression="0.4" spring="0.7" damp="3.0">
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2003-05-07 01:52:04 +00:00
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<control-input axis="/controls/gear/wheel[0]/brake" control="BRAKE"/>
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<control-input axis="/controls/gear/parking-brake" control="BRAKE" split="true"/>
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<control-input axis="/controls/gear/gear-down" control="EXTEND"/>
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<control-speed control="EXTEND" transition-time="6"/>
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<control-output control="EXTEND" prop="/gear/gear[0]/position-norm"/>
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</gear>
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<!-- right main -->
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2003-05-16 18:26:33 +00:00
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<gear x="-2.79" y="-1.81" z="-2.20" compression="0.4" spring="0.7" damp="3.0">
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2003-05-07 01:52:04 +00:00
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<control-input axis="/controls/gear/wheel[1]/brake" control="BRAKE"/>
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<control-input axis="/controls/gear/parking-brake" control="BRAKE" split="true"/>
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<control-input axis="/controls/gear/gear-down" control="EXTEND"/>
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<control-speed control="EXTEND" transition-time="6"/>
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<control-output control="EXTEND" prop="/gear/gear[1]/position-norm"/>
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</gear>
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<!-- Guess on wing tank positions -->
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<tank x="-3.20" y="1.0" z="-0.61" capacity="726"/>
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<tank x="-3.20" y="-1.0" z="-0.61" capacity="726"/>
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<tank x="-5.00" y="0" z="0" capacity="671"/>
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<!-- pilot -->
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<ballast x="-4.495" y="0" z="0.689" mass="180"/>
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<!-- armament -->
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<!-- Had too much weight I think...disable until stall speed fixed
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<ballast x="-3.20" y="0.7" z="-0.60" mass="800"/>
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<ballast x="-3.20" y="-0.7" z="-0.60" mass="800"/>
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-->
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<!-- prop -->
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<!--
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<ballast x="0.1" y="0" z="0.0" mass="200"/>
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-->
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</airplane>
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