Side

[sanhozay]

Stupid question:

Code: Select all

<function name="aero/force/Side_beta">
  <description>Side force due to beta</description>
  <product>
    <property>aero/qbar-psf</property>
    <property>metrics/Sw-sqft</property>
    <property>aero/beta-rad</property>
    <value> -1.0907 </value>
  </product>
</function>

Why would side force depend on wing area? Is it just a way of estimating overall dimensions of tail and fuselage for an aircraft of conventional shape?

[bomber]

Oh I love these political storms....

In short the answer is yes.... however ask yourself the question "were they actually interested in side ?" And the answer to that is no, because they're only interesting in understanding side in a very narrow minded band of a few degrees....

An aerodynamics experts isn't a flight modeller, they couldn't flight model their way out of a paper bag and if they did it'd be in a very narrow flight envelope.

So when you read anything written by them, take it on board.... and then ask them "does that work in real-time ?"..

Simon

[bomber]

And a question for all....

Why question just side ?

Code: Select all

    <function name="aero/force/Lift_elevator">
       <description>Lift due to Elevator Deflection</description>
       <product>
           <property>aero/qbar-psf</property>
           <property>metrics/Sw-sqft</property>
           <property>fcs/elevator-pos-rad</property>
           <value> 0.3929 </value>
       </product>
    </function>

I mean you know the size of the elevator, so why use the wing area ?

[IAHM-COL]

you call this political storm?
I call this a thread that's way beyond what I can grasp and comprehend what the fuzz is all about.

[bomber]

Well I could always try saying that on the other forum and we could see the results

[IAHM-COL]

ok.

back in topic, so what does side force depend upon? and why can't it be coded with a more proper surface? or can it, but it just not done that way? and is this a JSBsim dependency, or just how the Beagle was coded, and can be changed just fine?

[bomber]

It can be changed just fine, you just have to go against tradition.

You end up asking yourself "just what is side force ?"

If you think of it simply it's the lift vector generated by the v-stab with beta angle.... very similar to the lift vector generated by the wings/h-stab with alpha angle.

But that's not all side is... because the wing dihedral creates a force that can be split up into the vectors of lift, side and drag.... side exists when you have a wing dihedral, with no wing dihedral no side vector other than that generated by the v-stab.

so hold onto your head because I don't want it to explode.. side generated by the wing is about sine dihedral angle and the current sine beta angle.

Boooooooom !

Simon

[IAHM-COL]

slow with me


So
1) side force you describe as a lift force. Does it mean vectorially perpendicular to weight? or does it have components related to thrust and drag as well? (or maybe more interesting with yaw forces?)

2) you describe it also as a force with multiple components, some produced by the vstab and others by the wing surface. Then initially you said, you can actually code it differently if you beat convention (for which I am ok with). So the question now is can you have a multivariate for input and account for both (or more) required components?

Whether is sine or cosine (or more exotic radian funtions) of which particular angle should be ok, ultimately, the first question to solve is who are independent variables in the function to calculate.

[bomber]

you see that's the problem when you try to describe something using a system developed by bicycle salesmen..

[IAHM-COL]

(or maybe more interesting with yaw forces?)

My point being that I am imagining a craft thats flying kind of horizontally (not in a dramatically banked turn) then I see how the V.Stab does not offer much of a surface to the wind tunnel as to generate lift in oppose to yaw (read slip).