DFW-CV

[D-ECHO]

Which functionality, actually?

[bomber]

Actually in the real planes, they have the advantage of a strong prop blast and if you push the stick forward while gunning the engine, also while feeding in generous rudder, the prop's airstream will assist in turning the planes. Most of my aircraft has a weakly effective, steerable tail bogey to simulate this, since both YASim and JSBSim have little or no flight modeled tail surface aero effects while at taxi speeds.

[D-ECHO]

Well, as far as I understand what Lester writes, it would have to be coded into JSBSim...

[bomber]

No it doesn't have to be coded into JSBsim..... there just needs to be a force created that effects the plane using existing JSBsim functionality.

[Richard]

Simon's right the aerodynamic effects need to be added to the model not into the "code" as it is quite aircraft and geometry specific.

You could probably get some improvements just with a couple of tables based on the difference in freestream velocity from the propellers. As usual figuring out the numbers is going to be the hard but; but VSPAero does have support for propellers so that might be one possibility.

Interesting paper: http://m-selig.ae.illinois.edu/pubs/Sel ... eroSim.pdf

[LesterBoffo]

Why not simply add the functionality to the JSBsim model ?

There is a JSBsim code, but I've found it doesn't work all that well.

Snippet for example..

Code: Select all

    <function name="aero/qbar_tail-psf">
      <description>Thrust tube effects at tail</description>
      <sum>
          <property>aero/qbar-psf</property>
          <product>
            <property>forces/fbx-prop-lbs</property>
            <value>0.011</value>
          </product>
      </sum>
    </function>

In fact it doesn't work worth squat.

Here's your chance to lay into me for my liking YAsim.. I frankly don't want to build any WWI planes with any other FDM except YAsim, it builds aircraft from the actual 3D model's aerodynamics. Yeah I know, "blah blah, but it's not air tunnel accurate..." Point me to an online source of WWI aircraft that have been thoroughly air tunnel tested. You know, the full monty with tables and such.

[LesterBoffo]

Well, as far as I understand what Lester writes, it would have to be coded into JSBSim...

Which is another way to say it isn't natively coded. That you have to add the effect as an afterthought. The coding for JSB sim is flexible, but still, it's still less developed than two really old simulators that came out in the early 2000's, both of which had prop flow flight modeling on the tail surfaces, natively, in their coding, and it worked like it was supposed to..

I'll take a wild stab at why this is. JSB sim was never originally intended to model propeller powered aircraft dynamics. Wasn't one of Jon Bernst's statements about JSB sim was to be used to model modern jet aircraft dynamics? There's been some additions, but on the whole it's a jet aircraft flight simulation .exe, and on top of this it's not really based on the actual shape of the aircraft, doesn't allow for extra wings with out complex additions, you have to make estimations and look up wing air tunnel data tables.

Here's a thought for Simon. Even Targetware 0.64's very granular FDM is light years ahead of an FDM you can make from an Aeromatic based, but thoughtfully adjusted, JSBsim FDM. And guess what, 0.64 models propeller blast/tail effects, natively.

[LesterBoffo]

Its fun to see these planes in so reduced size for simulation

My background has been with model airplanes since I was a teenager, I started with rubber powered freeflight and progressed to scale model rubber freeflight and then control-line and R/C, the breakthrough was when electric RC models became practical in 1/12th scale and smaller.

Because suddenly the ability to make very light scale planes that were powered by scale sized slow turning propellers became technically feasible.

Some models I've built.

[IAHM-COL]

great art lesbof

[LesterBoffo]

great art lesbof

Thanks, yeah that little Nieuport 17 is still my favorite model to fly.

It has all the quirks of the full scale Nupe on a really compressed inertial/time scaling, you really have to 'dance on the sticks' to keep it heading straight while it transitions from tail down taxiing to bouncing along on the mains just before takeoff.