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New historically realistic Sopwith Camel JSBSim FDM released

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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby LesterBoffo » Tue Apr 02, 2013 6:40 pm

I've got the airfoil lift and drag polars from my Eastbourne Monoplane, and Sopwith One and one half-strutter if you wish to give them a try. They're in JSB sim formatting. Can't vouch for their complete historical accuracy, but they were derived from historical airfoil profiles drawn into XFLR5 at what I hope are close Reynolds numbers.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Bomber » Tue Apr 02, 2013 9:45 pm

Crickey Flug's alive ?

I shall download this FDM and have a look at it...

Simon
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchel
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Bomber » Tue Apr 02, 2013 10:12 pm

DFaber wrote in Sun Mar 31, 2013 10:55 am:I'm afraid this is a myth.
No Combat pilot over Enemy Territory, in unclear weather or uncertain altitude is going to try fancy Aerobatic manouvers which may lead to loss of control or disintegration of his Aircraft. Lots of WW2 Aircraft Manuals prohibit such manouvers in Combat and the major part of current day Combat Jet Manuals consists of Diagrams to give the Pilot an Idea of how not to leave the envelope and risk an expensive Airplane.
Apart from that, the main advantage of a Fighter Pilot is Altitude and Speed, a situation well within the envelope.

No sane Pilot who is aware how far he has to walk home will intentionally leave the safe margins of his Aircraft.


I can't even get my head around why this is sooooo wrong...... but I'll give a couple of reason's why this 'was' true during WWI and WWII...

1) The relative age and experience of these pilots
2) Self preservation
3) The fact that an engine can be pushed to 110% of it's rated power means it will be... because it aint worth my arse.

Just ask Captain Kirk, do you see him saying to Scotty "Oh yeh you're quite right, back it off a bit lads the dylithium crystals are getting a tad warm !"

And the most important....

4) I'm a design engineer and I'll give you a value for every question you ask, but I'll not give you one that if you fly to it, you'll do damage... Now you go fly the plane.

Simon
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchel
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Wed Apr 03, 2013 8:09 am

I've created an updated version incorporating ideas from the comments above, plus some others I came across:

http://brenthugh.com/flightgear/sopwith ... Sim-11.zip

Main updates:

- Updated critical angle of attack to 14 degrees, made many other related adjustments

- Removed code that reverses the direction of the gyroscopic effect, because it causes some strange feedback problems. So we'll just have the deal with the fact the gyroscopic effect is backwards for now.

- (Big one) Made numerous tweaks to ailerons & related effects--now more properly reflects the large drag, adverse yaw, and relative ineffectiveness despite the very large surface area of the ailerons. This makes a big difference in how it flies and seems to fit much closer with the descriptions of pilots

- Tweaked the spin characteristics quite a bit--I think they work better now and are more in line with reported behavior (though work may still remain)
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Wed Apr 03, 2013 8:17 am

AndersG wrote in Tue Apr 02, 2013 6:09 pm:
Buckaroo wrote in Tue Apr 02, 2013 5:39 pm:I saw it once in a NACA report, but now the danged NASA technical reports server isn't available to the public due to some danged reaction to some danged alleged Chinese espionage so I can't call it up again. @#$%!


Fortunately, the British have a copy of the NACA archive... :) http://naca.central.cranfield.ac.uk/

Nice work, btw!


Aha, thank you!

Have you checked the propeller/engine <sense> element for setting the direction of the gyroscopic effects? (I think it ought to affect them.)


I did - and you're right, if you reverse the 'sense' the gyroscopic effect is reversed.

But also the torque is reversed and P Factor as well.

As near as I can tell, those are correct with the current sense, but the gyroscopic effect is reversed.

If you change the sense, then the gyroscopic effect is correct but torque & P Factor are reversed.

(And all these are quite confusing to think through so it's always possible I'm mixed up.)

(And this does give me the thought, perhaps it's better for now to reverse the Sense and have the gyroscopic effect right but torque & P Factor wrong--those are relatively less apparent in ordinary piloting of the Camel.)
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Bomber » Wed Apr 03, 2013 6:21 pm

On my Fokker Dr1 I used a sence of -1...

The engine here also has a clockwise rotation as seen from the pilots seat, resulting in a tight right turn with nose drop....

Flug you might want to have a look at it...

http://target4today.com/_t4t-aircraft_/T4T-Fokker.zip


Simon
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Wed Apr 03, 2013 11:17 pm

LesterBoffo wrote in Tue Apr 02, 2013 6:40 pm:I've got the airfoil lift and drag polars from my Eastbourne Monoplane, and Sopwith One and one half-strutter if you wish to give them a try. They're in JSB sim formatting. Can't vouch for their complete historical accuracy, but they were derived from historical airfoil profiles drawn into XFLR5 at what I hope are close Reynolds numbers.


Those would indeed be very interesting to have a look and perhaps use as a model--if you don't mind sharing.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Wed Apr 03, 2013 11:21 pm

Bomber wrote in Wed Apr 03, 2013 6:21 pm:On my Fokker Dr1 I used a sence of -1...

The engine here also has a clockwise rotation as seen from the pilots seat, resulting in a tight right turn with nose drop....

Flug you might want to have a look at it...

http://target4today.com/_t4t-aircraft_/T4T-Fokker.zip

Simon


That's very interesting indeed! The detail involved in the FDM is pretty astonishing.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Bomber » Thu Apr 04, 2013 2:48 pm

Thanks Flug,

The same drive for accuracy at and beyond the normal flight envelope for a WWI and WWII combat plane as you plus the ability to have even minor damage effect the flight characteristics was my goal..

But I also wanted to simplify the FDM process but increase the accuracy especially for planes where there's little to no data..... lets face it I was after the moon on a stick here.

Being concious that 3d modelers have to tendency to model a plane and then look to use 'any' similar FDM available to get their plane into the air I was wanting to improve that process such that they could modify a 'type' of FDM, such as a tri-plane, bi-plane, etc by imply modifying the 'mass_ballance' files with dimensional data that they already have and have used to model.. the mass for each area of a plane I determined could be calculated through density as the era of flight evolves and new materials are used... not the density of the material but of the volume used understanding that at the initiation of the era of flight the overall density of a volume of plane was low and this increased as more strength was required and more material was used, right up to the point where a change of material was required.

I'm happy with the aerodynamics of the FDM I have at present, but I'm not happy with the piston engine within JSBsim..

Have you ever done a static test of a piston engine in FG ?

Simon
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchel
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby LesterBoffo » Fri Apr 05, 2013 7:39 pm

flug wrote in Wed Apr 03, 2013 11:17 pm:
Those would indeed be very interesting to have a look and perhaps use as a model--if you don't mind sharing.


To be put in the '<axis name="LIFT">' section..

Code: Select all
<function name="aero/force/Lift_alpha">
      <description>Lift due to alpha</description>
      <product>
          <property>aero/qbar-psf</property>
          <property>metrics/Sw-sqft</property>
          <table>
            <independentVar lookup="row">aero/alpha-rad</independentVar>
            <tableData>
              -0.2793        -1.298   
              -0.1396        -0.5118   
              -0.1047        -0.3244   
              -0.0698        -0.1446   
              -0.0349        0.0581
               0.000         0.170
               0.01745       0.355   
               0.03491       0.536
               0.0428        0.69
               0.0523        0.84   
               0.06981       0.984   
               0.1047         1.045   
               0.1396         1.18   
               0.1745         1.316   
               0.1918         1.59   
               0.2443         1.565   
               0.2793         1.491   
               0.3142         1.383   
               0.3316         1.214   
               0.3491         1.191   
               0.3665         1.037   
               0.3840         0.8031   
               0.436         0.6785
            </tableData>
          </table>
      </product>
    </function>


and the '<axis name="DRAG"> sections..

Code: Select all
<function name="aero/coefficient/CD0">
                <description>Drag_at_zero_lift</description>
                <product>
                <property>aero/function/ground-effect-factor-drag</property>
                <property>aero/qbar-psf</property>
                <property>metrics/Sw-sqft</property>
          <table>
            <independentVar lookup="row">aero/alpha-rad</independentVar>
            <tableData>
                       -1.5700     1.500     
                       -0.280         0.794   
                       -0.140         0.251
                       -0.105         0.169
                       -0.070         0.0441
                       -0.035         0.018
                        0.000         0.0078
                        0.035         0.0114
                        0.087         0.0384
                        0.104         0.078
                        0.157         0.131
                        0.174         0.196
                        0.209         0.263   
                        0.244         0.386   
                        0.279         0.599   
                        0.314         0.827   
                        0.332         1.065   
                        0.349         1.3286   
                        0.366         1.3652   
                        0.384         1.4910   
                        0.419         1.494   
                        1.570        1.5000
            </tableData>
          </table>
       </product>
    </function>
hope these help. The Albatros DIII I was flying with you and your friend a couple days back uses a slightly modded version of this 'foil's data tables.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Thu Apr 11, 2013 7:18 pm

FYI I've released ver. 1.2 now:

http://brenthugh.com/flightgear/sopwith ... Sim-12.zip [ver 1.2, 4/10/2013

It incorporates
- More historically/aerodynamically accurate lift and drag curves
- More historically accurate aileron modelling (the Camel was piloted far more with the rudder than the ailerons, the ailerons were large, draggy, relatively ineffective, and induced a lot of adverse yaw)
- Specifically, the Camel won't even do a slow roll without a whole lot of coaxing, and when it does--23 seconds to complete the roll (according to an article by Brian Lecomber; see however the contrasting description in the Manouvres of Inverted Flight article; both are in the Historical Docs directory. I think they are just using the same term for a slightly different maneuver). This behavior still does not quite match the descriptions but it is a lot closer than it was.
- Both engine torque and (large) gyroscopic force due to the engine/propellor are accurately modelled (we work around the bug in JSBSim that reverses the gyroscopic force by putting sense=-1, which gives correct gyroscopic force but reverses the direction of the torque. The model then corrects the direction of the torque, which seems to work well. The previous method of reversing the direction of the gyroscopic force didn't work very well.)
- Tweaked the aircraft metrics to be more historically accurate
- Tweaked spin & stall characteristics to be more accurate according to descriptions
- The Camel can now fly inverted, which matches historical descriptions of its capabilities
- Many other minor tweaks and improvements

I am not sure that with all the adjustments to the FDM that the cruising speed, climb rate, and all those variables exactly match the historical Camel, as they did with earlier versions. That might require just a bit more tweaking, but this is getting close to what I'm capable of accomplishing with this now.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby myxa » Sat Apr 13, 2013 8:50 pm

Dear All,

I'm using Win7 x64 and installed FG 2.10.0.3

I have installed FlightSim Yoke and CH Rudder Pedals

When I'm trying to fly with Sopwith that included in default installer, I cannot run engine

There are two types of errors

1)
Engine is launched but unexpectedly shut down when I try to aply full throttle. Following text in the console

... running Camel utilities
Nasal runtime error: props.setDoubleValue() with non-number
at D:/Program Files/FlightGear/data/Nasal/props.nas, line 32
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 280
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 249
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 78


2)
Engine is launched but unexpectedly shut down when I try to move rudder. Following text in console

... running Camel utilities
Nasal runtime error: props.setDoubleValue() with non-number
at D:/Program Files/FlightGear/data/Nasal/props.nas, line 32
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 280
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 249
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 78

Shall I use new Sopwith release (v.1.2) instead of sopwith from default installer?

BTW, for v.1.2, I cannot run engine for JSBSim version
folowoing text in console

Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Nasal getprop: property /fdm[0]/jsbsim[0]/gear[0]/unit[6]/side_friction_coeff[0]
is NaN
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Camel/JSBSim: Aircraft friction parameters initialized
Nasal getprop: property /fdm[0]/jsbsim[0]/gear[0]/unit[11]/side_friction_coeff[0
] is NaN
Camel/JSBSim: Aircraft friction parameters initialized
Nasal getprop: property /fdm[0]/jsbsim[0]/gear[0]/unit[12]/side_friction_coeff[0
] is NaN

For YASim model, I can run the engine and fly

Thank you for your support
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Tue Apr 16, 2013 12:55 am

FYI I just released JSBSim Sopwith Camel 1.3, which incorporates a more historically accurate drag/lift table, based on historical wind tunnel data, but tweaked to closely match known Camel performance at cruise, climb, turns, etc.

In addition, this version has these features:

- More realistic start sequence
- Inverted flight possible
- Engine cuts out in inverted or negative-G flight, just as historical Camel's engine did
- Optional manual mixture control (fiddly engine controls were a prominent feature of the historical Camel)

Download ver 1.3 of the JSBSim Camel here:

http://brenthugh.com/flightgear/sopwith ... Sim-13.zip
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby myxa » Sun Apr 21, 2013 3:13 pm

Still cannot launch engine in v 1.3 (YASim)

... running Camel utilities
Nasal runtime error: props.setDoubleValue() with non-number
at D:/Program Files/FlightGear/data/Nasal/props.nas, line 32
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 280
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 249
called from: D:/Program Files/FlightGear/data/Aircraft/sopwithCamel/Models/fue
l.nas, line 78

in v1.2, JBSim version allowed to run engine but in 1.3, KBSim excluded, as I understood

PLease help

Thank you
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Bomber » Mon Apr 22, 2013 5:51 pm

Flug,

I love what you've done in the Documents section, it's spot on... I'm going to follow your lead on that.

Regards

Simon
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