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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 bugman » Sat Feb 25, 2017 1:36 pm

@flug: Considering that there is no one maintaining the Camel in FGAddon, have you thought of contributing back upstream and updating the JSBSim FDM and optional Bombable components directly in FGAddon?

Regards,
Edward
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Mon Feb 27, 2017 6:07 am

@flug: Considering that there is no one maintaining the Camel in FGAddon, have you thought of contributing back upstream and updating the JSBSim FDM and optional Bombable components directly in FGAddon?


Edward--

Thanks for asking. That is indeed what I would like to do and once I get this release wrapped up that is my thought for the next step.

FYI I thought the release was about ready to go, but got fiddling with it again today and made some further very substantial improvements in the engine management. It really starts to show what the aircraft was capable of when you can really control it. It is a heckuva lot of fun to fly--which is not necessarily something I would have said about it a few versions ago!

So--another pre-release should be available pretty soon, with some more major improvements. And--hopefully!--soon after that the final release, and then integration into FGAddon.
Last edited by flug on Mon Mar 06, 2017 4:48 am, edited 1 time in total.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Mon Feb 27, 2017 10:28 am

OK, the 2.0gamma release of the Camel is here:

https://github.com/bhugh/SopwithCamel-J ... 0gamma.zip

I'm hoping this will be the version that becomes the final release--so if anyone has time to give a quick check-out and let me know if you see any problems, I'd appreciate it.

You can also download the latest version Bombable, which includes the latest 2.0gamma Camel:

https://github.com/bhugh/Bombable/archive/4.6gamma.zip

Main updates:

- Major improvements in engine realism, control; blip & magneto system now works much better and is much more similar to the real Camel
- Refined engine settings; very close in speed, climb rate etc to historical Camel
- Updated documentation
- Included two HUDs, ultra-minimal.xml and ultra-minimal-pip.xml, that I like to use with the Camel (you'll have to copy these to the Huds directory and update your preferences.xml in order to use them.)
- More updates to sound and ground effects
- Many minor bug fixes

A few versions ago, I would have said the Camel is a bear to fly. Now, it's more of a joy. I can see why pilots really liked it.

It's amazing the way getting certain details really dialed in helps. In this case, the engine controls--magneto settings and blip switch--now give you feather-light control of the aircraft on touchdown and other similar situations. Suddenly it's possible to land on two wheels, set the tail down when you want to (or keep it up if you don't), do a touch-and-go where you keep the tail up, or set it down and touch and go. All the other things that (must have!) been routine for Camel pilots back in the day, but are really hard to nail down in a simulator.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Mon Feb 27, 2017 5:40 pm

wlbragg wrote in Thu Feb 23, 2017 5:41 am:@flug, nice!

I added the variant tag to see the JSBSim version along with the YASSim version. . . .

Also, I guess I don't have or it couldn't figure out the path to
Code: Select all
<keyboard include="../Generic/WalkView/walk-view-keys.xml">

So to get it to work at all I had to get rid of the include?


Thanks for these bits of feedback--FYI both are included and/or fixed in the latest version.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby wlbragg » Mon Feb 27, 2017 10:43 pm

It all appears to be working now but it's not easy to fly. My system may not be responsive enough to get the most out of this aircraft.

Thanks again!
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Mon Mar 06, 2017 5:11 am

wlbragg wrote in Mon Feb 27, 2017 10:43 pm:It all appears to be working now but it's not easy to fly. My system may not be responsive enough to get the most out of this aircraft.


I've been able to fly it Ok on as low as 20 FPS.

One tip (and something that could perhaps be implemented in the FDM to a degree): The controls are on the one hand, extremely sensitive in some situations. Pilots reported very sensitive controls, and that in many situations you barely had to nudge it to move the direction you want. And actually in many cases you give the 'nudge' to start a maneuver and then spend the rest of the maneuver gently/slightly countering your first nudge to keep the maneuver under control and from turning/rolling/whatever TOO fast.

(Reason for this is that the aircraft is so square--relatively long wings, relatively short tail. It barely wants to keep going straight, it won't stay in coordinated flight at all by itself, and it barely has a preferred 'frontwards' direction. So it only takes a little nudge to get it off that small region of stability, and then it can very, very easily go in all sorts of directions--most of which you want to prevent, if you want to live.)

But the flip side is, in many situations you don't really have enough control authority. So you're flying along with full right rudder and really you need about another 50-100% right rudder to have the control authority you want or need.

(Reason for this is again the relatively short body, meaning rudder & elevators have relatively little leverage, plus relatively small area of control surfaces for the elevator and, especially, the rudder. The ailerons are a different matter: They are just huge barn-door type affairs, they are very early and unrefined--just a year or two beyond the 'wing warping' stage of roll control--and the 'unintended' side effects of drag and adverse yaw have nearly as much effect on the aircraft as the intended roll moment. So, you tend to initiate rolls moreso with the rudder than with the ailerons.)

TL;DR of the above is that sometimes the slightest breath of input to the controller has a HUGE impact, other times cranking your controller to the max doesn't have enough impact.

This, plus the fact that you have to fly the aircraft at every moment, to basically manhandle it to do what you want constantly, make it quite a bear to handle.

All this is leading up to my point: You might benefit from putting a <power> line into your joystick config for rudder, elevator, and maybe aileron, too. Something like this:

Code: Select all
  <axis n="3">
    <desc>Rudder</desc>
    <dead-band type="double">0.005</dead-band>
    <binding>
      <command>property-scale</command>
      <property>/controls/flight/rudder</property>
      <factor type="double">.75</factor>
      <offset type="double">0</offset>
      <power type="int">3</power>
    </binding>
  </axis>


You could try <power type="int">3</power> or <power type="int">2</power> or maybe even <power type="int">4</power>. What it will do is lower the sensitivity in the central area of the joystick, so that you have a lot more control. But you will still get full possible control authority when you move from the center to the limits of stick movement. It's surprisingly helpful.
Last edited by flug on Mon Mar 06, 2017 5:27 am, edited 1 time in total.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Mon Mar 06, 2017 5:24 am

Also, the controls are purposefully quite a bit out of trim--because that is the way real Camels flew. Pilots had to keep a fairly strong forward pressure on the stick at all times just to maintain level flight. If you let up on that, you'll climb, then stall--and the stall can be quite difficult to recover from.

Simultaneously, it takes constant rudder input just to keep the aircraft in somewhat coordinated flight and going straight--ie, not constantly turning.

Those are both exactly as report in by pilots of real Camels. And the Camel had no way to trim out the controls. Pilots simply held the rudder and stick in place--wherever that place was.

But for practical flying purpose in FlightGear, it might be wise to just assign some rudder, elevator, and maybe aileron trim keys or buttons, and just trim out the elevator, then the rudder and/or ailerons.

Once it's trimmed out nicely it's maybe not completely authentic, but it behaves a lot more they way you might expect--overall, a lot easier to handle.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Mon Mar 06, 2017 5:31 am

One last tip: Be sure to read the in-sim aircraft help (display via the '?' key). It has all sorts of suggestions and practical tips for dealing with liftoff, landing, stall, etc etc etc.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby wlbragg » Mon Mar 06, 2017 6:34 am

flug wrote in Mon Mar 06, 2017 5:11 am:[And actually in many cases you give the 'nudge' to start a maneuver and then spend the rest of the maneuver gently/slightly countering your first nudge to keep the maneuver under control and from turning/rolling/whatever TOO fast.


Also, the controls are purposefully quite a bit out of trim--because that is the way real Camels flew. Pilots had to keep a fairly strong forward pressure on the stick at all times just to maintain level flight. If you let up on that, you'll climb, then stall--and the stall can be quite difficult to recover from.

Simultaneously, it takes constant rudder input just to keep the aircraft in somewhat coordinated flight and going straight--ie, not constantly turning.

Those are both exactly as report in by pilots of real Camels.


I'd say you got it dialed in quite nicely then because these "features" are quite noticeable and you described what I was experiencing to a tee!

My next session will make more sense now and provide even more enjoyment having some context behind it.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Tue Mar 07, 2017 2:43 am

One other tip: Beware of the wind.

I've been practicing quite a bit in the Camel and still in some fairly stiff crosswinds & tailwinds I just can't get it up.

There is a reason they always took off into the wind and also a reason they simply cancelled missions on days that were too stormy or windy, back in the day . . .

Obviously even today planes take off more or less into the wind and there is a limit to how strong a crosswind you can land any given plane in. But my impression is that the aircraft from this era were much less capable of handling, say, a strong crosswind on takeoff or landing than most planes today.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby AndersG » Tue Mar 07, 2017 9:35 am

It is also worth noting that an "airfield" of the day usually was just that - an open relatively smooth piece of land - there were no runways as such, so landing and take off was always into the wind (space permitting).

(Even in the 1950s some Swedish military pilots got their basic flight training on grass airfields and as a consequence had very poor cross wind technique when they moved up to jet aircraft that operated from surfaced runways.)
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Johan G » Tue Mar 07, 2017 12:36 pm

AndersG wrote in Tue Mar 07, 2017 9:35 am:[...] and as a consequence had very poor cross wind technique when they moved up to jet aircraft [...]

That in addition to transitioning to swept wings that did not like being flown uncoordinated, in particular at approach airspeeds. That there was no two-seat trainer probably did not help either. (Primarily speaking of the Saab J 29 Tunnan / "Flying barrel".)
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby LesterBoffo » Tue Mar 07, 2017 2:08 pm

The airfields of WWI were what ever somewhat level, open, hay fields they could find. There was enough knowledge about the prevailing wind patterns that the fields chosen were, generally aligned with the wind along their longest dimension. The takeoff points were also set into one of the corners so there was a choice of direction into the wind. Some fields were notoriously bad for cross winds and up-wind rotors, Corcieux and Nancy-Malzeville were both tricky.

The trim issues with the Camel for the most part, were because of Sopwith of moving the fuel tank from the upper forward fuselage to behind the pilots seat, to clear space for the second MG. So there was a lot more rearward CG shift as you filled the fuel tank. The early Camels with the lighter LeRhone 130 were more susceptible to stalling and spinning in on take off with a inexperienced pilot, partly because the LeRhone was less powerful, so you had to let it climb on it's wings. Wings from that era had a very narrow AoA lift zone and could be stalled quite easily if pulled into too high an AoA while at low speed. Another reason why it was good practice to get the tail up early in your take off and let it climb out with little elevator assistance.
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby Bomber » Wed Mar 08, 2017 7:30 pm

flug wrote in Mon Feb 27, 2017 10:28 am:OK, the 2.0gamma release of the Camel is here:

https://github.com/bhugh/SopwithCamel-J ... 0gamma.zip

I'm hoping this will be the version that becomes the final release--so if anyone has time to give a quick check-out and let me know if you see any problems, I'd appreciate it.



First thing I'd say is well done for including all the documentation it's the way to go.


As for the flight model... I build and fly models for 50hz and your camel doesn't sit at all on the ground at that frequency.

Just did a drop test and it glides at 38kts... considering it's stall speed is 41kts I'd have expected a glide around the +20kts mark so 61kts.
It also has a lift to drag ratio of >14.... should be about 8.

Regards

Simon
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Re: New historically realistic Sopwith Camel JSBSim FDM rele

Postby flug » Thu Mar 09, 2017 9:35 pm

Bomber wrote in Wed Mar 08, 2017 7:30 pm:As for the flight model... I build and fly models for 50hz and your camel doesn't sit at all on the ground at that frequency.


Simon,

I must confess I don't understand the above sentence at all. Could you explain or expand a bit? What kind of changes are likely required to make it fit this criterion?
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