On Mon, 3 Jul 2006, Maik Justus wrote:
All effects I have only tested with the bo. But I will check everything
with the ch47 after finishing the coding. Please send me your ch47
config (or is it in cvs?). Probably there are some wrong signs for
clockwise rotating rotors. But the sign of the torque seems to be
correct; if not the ch47 would not be flyable.
Attached the yasim config file here (in case anyone else wish to try it too),
plus a readme.txt with some data I gathered about the aircraft so
far.
This configuration is not tested /without/ the patch to
::solveHelicopter(). It will most likely behave very differenly (and
possibly severly instable) with an unpatched fgfs. It can't reach cruise
speed with the modified solver (too much drag).
Longitudal cyclic pitch trim is set manually for both rotors via the
/engiges/engine[0]/propeller-pitch property. (simple 0--4° fwd on both
rotors. Doesn't seem to have much effect though.)
Oh and I use an inner payload set by a property from the menu.
<weight n="0">
<name>Internal cargo</name>
<weight-lb>0</weight-lb>
<max-lb>27000</max-lb>
</weight>
...could use more of them to trim the CG during test flights.<airplane mass="23090">
<!-- Approach configuration -->
<approach speed="50" aoa="0">
<control-setting axis="/controls/engines/engine[0]/throttle" value="0.1"/>
</approach>
<!-- Cruise configuration -->
<cruise speed="150" alt="0">
<control-setting axis="/controls/engines/engine[0]/throttle" value="0.7"/>
</cruise>
<rotor name="fwd" x="-2.18" y="0.0" z="2.57" nx="0.1584" ny="0" nz="1." fx="1"
fy="0" fz="0"
mincollective="1" maxcollective="18"
mincyclicele="-4" maxcyclicele="4"
mincyclicail="-18" maxcyclicail="18"
diameter="18.29" numblades="3" weightperblade="357" relbladecenter="0.5"
dynamic="1" rpm="225" rellenflaphinge="0.0222" delta3="0.0"
translift="0.05" ccw="1" delta="0.8"
pitch_a="18" forceatpitch_a="25000"
pitch_b="18" poweratpitch_b="3000"
flapmin="-18"
flapmax="30"
flap0="-4.75"
flap0factor="1"
poweratpitch_0="100"
notorque="1"
dragfactor="1"
>
<control-input axis="controls/flight/rudder" control="CYCLICAIL"
src0="-1.0" src1="1.0"
dst0="-1.0" dst1="1.0"/>
<control-input axis="controls/flight/aileron" control="CYCLICAIL"
src0="-1.0" src1="1.0"
dst0="-1.0" dst1="1.0"/>
<control-input axis="controls/flight/elevator" square="0" control="COLLECTIVE"
src0="-1.0" src1="1.0"
dst0="1.0" dst1="-1.0"/>
<control-input axis="controls/flight/elevator-trim" control="COLLECTIVE"
src0="-1.0" src1="1.0"
dst0="0.5" dst1="-0.5"/>
<control-input axis="controls/engines/engine[0]/throttle" control="COLLECTIVE"
src0="0.0" src1="1.0"
dst0="1" dst1="-1"/>
<control-input axis="controls/engines/engine[0]/magnetos"
control="ROTORENGINEON"/>
<control-input axis="controls/engines/engine[0]/propeller-pitch"
control="CYCLICELE"
src0="0.0" src1="1.0"
dst0="0" dst1="1.0"/>
</rotor>
<rotor name="aft" x="-14.034" y="0.0" z="3.991" nx="0.0699" ny="0" nz="1."
fx="1" fy="0" fz="0"
mincollective="1" maxcollective="18"
mincyclicele="-4" maxcyclicele="4"
mincyclicail="-18" maxcyclicail="18"
diameter="18.29" numblades="3" weightperblade="357" relbladecenter="0.5"
dynamic="1" rpm="225" rellenflaphinge="0.0222" delta3="0.0"
translift="0.05" ccw="0" delta="0.8"
pitch_a="18" forceatpitch_a="25000"
pitch_b="18" poweratpitch_b="3000"
flapmin="-18"
flapmax="30"
flap0="-4.75"
flap0factor="1"
poweratpitch_0="100"
notorque="1"
dragfactor="1"
>
<control-input axis="controls/flight/rudder" control="CYCLICAIL"
src0="-1.0" src1="1.0"
dst0="1.0" dst1="-1.0"/>
<control-input axis="controls/flight/aileron" control="CYCLICAIL"
src0="-1.0" src1="1.0"
dst0="-1.0" dst1="1.0"/>
<control-input axis="controls/flight/elevator" square="0"
control="COLLECTIVE"
src0="-1.0" src1="1.0"
dst0="-1.0" dst1="1.0"/>
<control-input axis="controls/flight/elevator-trim" control="COLLECTIVE"
src0="-1.0" src1="1.0"
dst0="-0.5" dst1="0.5"/>
<control-input axis="controls/engines/engine[0]/throttle" control="COLLECTIVE"
src0="0.0" src1="1.0"
dst0="1" dst1="-1"/>
<control-input axis="controls/engines/engine[0]/magnetos"
control="ROTORENGINEON"/>
<control-input axis="controls/engines/engine[0]/propeller-pitch"
control="CYCLICELE"
src0="0.0" src1="1.0"
dst0="0" dst1="1.0"/>
</rotor>
<cockpit x="-1.88" y="0" z="0.6"/>
<!-- main body -->
<!-- README.yasim says "taper" is fraction of "radius". ...not width?? -->
<fuselage ax="-0.5" ay="0" az="0" bx="-16" by="0" bz="0"
width="2.5" taper="0.5" midpoint="0.5"/>
<!-- left engine, x uncertain -->
<fuselage ax="-11.2" ay="1.22" az="1.68" bx="-13.5" by="1.22" bz="1.68"
width="0.8" taper="0.1" midpoint="0.5"/>
<!-- right engine -->
<fuselage ax="-11.2" ay="-1.22" az="1.68" bx="-13.5" by="-1.22" bz="1.68"
width="0.8" taper="0.1" midpoint="0.5"/>
<!-- Aerodynamic effect of the fuel tank sidesteps? And what about the
swept up stern? Is the fwd pylon a h+vstab or a pure drag element? -->
<!-- fwd pylon, as drag -->
<fuselage ax="-1" ay="0" az="1.8" bx="-3.0" by="0" bz="1.8"
width="1.0" taper="0.1" midpoint="0.3"/>
<!-- aft pylon, as a vstab -->
<vstab x="-14" y="0" z="1" taper="1"
length="2.5" chord="4.5" sweep="0">
<stall aoa="30" width="20" />
</vstab>
<gear x="-6.15" y="1.78" z="-1.80" compression=".2" spring="3"> <!-- left fwd
-->
<control-input axis="/controls/gear/brake-left" control="BRAKE" />
<control-input axis="/controls/gear/brake-parking" control="BRAKE" />
</gear>
<gear x="-6.15" y="-1.78" z="-1.80" compression=".2" spring="3"> <!-- right fwd
-->
<control-input axis="/controls/gear/brake-right" control="BRAKE" />
<control-input axis="/controls/gear/brake-parking" control="BRAKE" />
</gear>
<gear x="-13.08" y="1.78" z="-1.70" compression=".2" spring="3"> <!-- left aft
-->
<control-input axis="/controls/gear/brake-left" control="BRAKE" />
<control-input axis="/controls/gear/brake-parking" control="BRAKE" />
<control-input axis="/controls/gear/tailwheel-lock" control="CASTERING"
src0="0.0" src1="1.0"
dst0="1.0" dst1="0.0"/>
</gear>
<gear x="-13.08" y="-1.78" z="-1.70" compression=".2" spring="3"> <!-- right
aft -->
<control-input axis="/controls/gear/brake-right" control="BRAKE" />
<control-input axis="/controls/gear/brake-parking" control="BRAKE" />
<control-input axis="/controls/gear/tailwheel-lock" control="CASTERING"
src0="0.0" src1="1.0"
dst0="1.0" dst1="0.0"/>
</gear>
<tank x="-9.47" y="1.36" z="-.68" capacity="75"/>
<tank x="-9.47" y="-1.36" z="-.68" capacity="75"/>
<tank x="0" y="0" z="0" capacity="0"/> <!-- work around bug in
native_fdm.cxx:184 -->
<tank x="0" y="0" z="0" capacity="0"/>
<ballast x="-2.0" y="-0.33" z="0" mass="180"/> <!-- pilot -->
<ballast x="-2.0" y="0.33" z="0" mass="180"/> <!-- copilot -->
<ballast x="-1.0" y="-.0" z="0" mass="200"/> <!-- cockpit -->
<!-- left engine, x is estimated -->
<ballast x="-12" y="1.22" z="1.68" mass="640" />
<!-- right engine -->
<ballast x="-12" y="-1.22" z="1.68" mass="640" />
<ballast x="-5.00" y="0" z="0" mass="9000"/> <!-- Yasim bug kludge-->
<ballast x="-12.00" y="0" z="0" mass="9000"/> <!-- Yasim bug kludge-->
<ballast x="-6.5" y="0" z="-1" mass="2000"/> <!-- Trim ballast -->
<!-- Ideal CG: -8.330m. "Empty" (stripped): -8.66m-->
<weight x="-8.33" y="0" z="0" mass-prop="/sim/weight[0]/weight-lb"/> <!-- inner
payload -->
</airplane>
Datum used: x=0 at tip of pitot tube in the nose. (See Boeing drawing)
CG limits and calculations, see chapter 6 in TM 1-1520-240-10 (Operator's
manual) "station 328" at x=-8.33m is a good aim for CG
(for max speed and gross wgt)
Boeing drawing (dated year 1977) states:
(with reference to datum line between rotors at station 331")
Empty: 9.9 in aft, i.e. 331+9.9=340.9" (or x=-8.66 m)
Most fwd (33000lbs gross weight): 23.1" fwd, 331-23.1=307.9", (x=-7.82m)
Most aft (33000lbs gross weight): 12.0" aft, 331+12=343" (x=-8.71 m)
Gross wgt has been increased since 1977, to 50000lbs. (engine upgrade etc)
Values for Z axis CG not yet found. Measured from drawing, for empty is
about 20" above datum, i.e. z=0.51m
Tanks are located with centre about 0.5m below datum. (Exact numbers in
Operator's manual)
NB! "Empty" is very empty. Not including various standard equipment.
Data from Boeing drawing for CH-47D model:
Blade pitch range for fwd rotor: -19.3 to 39.3
Blade pitch range for aft rotor: -22.5 to 36.2
(not sure how to use this information)
Blade twist: 12°
(not yet implemented in the FDM engine)
Flap hinge at radius: 8"
Lead-lag hinge at radius: 29.5"
(both with dampers)
Coning stop angle: 30°
Droop stop fwd rotor: -4.75°, aft: -5.75° "in flight" (-1.5° "static"?)
(there are more numbers on the drawing, not sure what they mean. The
droop stops are retracted somewhat when rotors are operating.)
Collective pitch (thrust): 1 to 18°
(i.e. /both/ rotors -- ?)
Ground detent for thrust lever: 3° (to avoid droop stop pounding)
Normal rotor rpm: 225
Autorotation max rpm: 244
Forward rotor shaft leans forward 9° (tan(9°) yields ~0.1584 for nx
Aft rotor shaft leans forward 4° (tan(4°)= 0.0699
The Chinook is equipped with dual "Advanced Flight Control System", AFCS.
The AFCS controls, amongst other things, "longitudal cyclic trim", LCT.
(Which in Yasim means adjusting CYCLICELE on each rotor. Elevator on a tandem
helicopter is set by using differential "collective" between fwd and aft
rotor.)
CH47 Theory of Operations, page 11-5:
19. Longitudinal Cyclic Trim
Reduces flap-back to relieve bending stresses particularly on
rear rotor shaft. In its automatic mode of operation, airspeed
and altitude signals are processed by the AFCS units and used
to position the two LCP actuators; the forward is controlled by
the No. 1 AFCS unit, the aft by the No. 2 AFCS. When the
aircraft clears the ground, the actuators retract from their
ground position. At sea level, beyond 60 knots, the forward and
aft actuators remain retracted, positioning the rotor disc
planes relative to their masts by 1.2° and 3.25° respectively.
From 60 knots to 150 knots, the actuators increase cyclic pitch
linearly to 4° forward on both rotors. With increasing
altitude, the LCT program is advanced. Provided that the AFCS
units are receiving electrical power, LCT automatic operation
continues. Driving signals are routed through the AUTO/MAN
switch on the AFCS panel. Setting the switch to MAN
disconnects signals from both AFCS units and permits manual
operation of the LCT.
AFCS to be implemented. Meanwhile, manual LCT can be set using the
propeller pitch control. Not clear if the disc plane positions below 60kts
means they are leaning fwd or aft or one of each, nor what their positions
are on the ground. But from 150kts and above (and above some unknown
altitude, according to one pilot: in a hover at atmospheric altitude of
15000 feet, or less) both LCP actuators are fully extended: i.e. 4° fwd on
both discs.
Rear wheels are castering with swiwel locks, but one (the left one?) also
has power steering. Both rear gears have ground contact switches which are
used for various automatic functions, including halving stick sensitivity
in pitch axis.
Engines: assume the (modified) T55-GA-714A described in Theory of
Operations. Weight (complete with transmission) 1411bs (640kg)
Max power (10 minutes) 4867 "horsepower"(?) (3629kW <-- assuming shp)
Emergency power (2 minutes) 5069 (3780kW)
(more data in TO)
======================
Sources of information:
http://www.chinook-helicopter.com/
(Boeing drawing from there someplace)
where manuals in PDF can be downloaded at:
http://www.chinook-helicopter.com/Publications/Publications.html
In particular (from above web page):
CH47 Theory Of Operations
and
TM 1-1520-240-10 (Operator's Manual For Army CH-47D Helicopter)
Chinook pilots discussions:
http://www.pprune.org/forums/
(Section Rotorheads. See archive.)
There is also a pdf in circulation giving some information about a ch47d
simulator, google for "chinook_boeing1c.pdf". It comes from the
investigation (UK House of Lords) of the Mull of Kintyre accident.
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Flightgear-devel mailing list
Flightgear-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/flightgear-devel
