Changes in handling flaps with Nasal in FG 3.6

[vanosten]

Hi

I am a bit confused about how to make joystick assignments for flaps in FG 3.6 RC.

The following worked fine in earlier versions across aircraft and still works with e.g. aircraft=cap10c:

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controls.flapsDown(1);
settimer(func { gui.popupTip(sprintf("Flaps: %.2f", getprop("/controls/flight/flaps")));}, 3);


However when I use the same with aircraft=extra500 or aircraft=c172p nothing happens.

Contrary to this the following does not seem to work anymore with cap10c, but works fine with extra500 or c172p.

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setprop("/controls/flight/flaps", 0);
gui.popupTip("Flaps fully retracted");


Looking at the internal properties browser there also seems to be a difference between aircrafts whether I should have a look at /surface-positions/flaps_pos_norm or /controls/flight/flaps to get the current value.

And then in $FGDATA/Nasal/controls.nas ca. line 130 it states

# Wrapper around stepProps() which emulates the "old" flap behavior for configurations that aren't using the new mechanism.

Well if this is the old way, where can I find the new way?

=> Could someone resolve my confusion and point me to code/properties, which work across aircraft?

Thanks a lot.

[Thorsten]

The default chain seems to be:

* '[' and ']' have key bindings to call controls.flapsDown(1) or controls.flapsDown(-1) respectively (keyboard.xml)

* flapsDown sets /controls/flight/flaps (dependent on whether /sim/flaps exists, there are two different ways to compute the effect, but they all end up in the same property) (controls.nas)

* from there for JSBSim it would end up as /fdm/jsbsim/fcs/flap-cmd-norm

* how the airfoil actually moves is then up to JSBSim (for instance, if a hydraulics system is not active, JSBSim may not translate the command into an actual movement).

* for YaSim I don't know for sure

Any aircraft may override the chain at any point. For instance the Space Shuttle doesn't have classical flaps, and the key bindings are instead used for the yaw control of RCS thrusters. The body flap is trimmed up and down by 'f' and 'shift+f' which have their own associated Nasal script and set a separate property, so /controls/flight/flaps never has any meaning - so there is no fully generic solution. Also, it usually makes a difference whether the controls have issued a command and whether an airfoil actually moves - they are different properties *-pos-norm vs. *-cmd-norm for instance.

I've seen flap implementations which are continuous and those which go in steps, and there are a few exotic cases of flaps going both directions (like for the Shuttle). I guess the safest bet is to target /controls/flight/flaps - this should cover most.

[vanosten]

Thank you for the answer. So handling depends on the flight dynamics model and the real aircraft. However the the aircraft modeller should know both. If we assume that the modellers are pretty consistent (at least when it comes to core stuff) in assigning keyboard commands, then the question (which I could not find a function for) is: can one emulate hitting a keyboard key from Nasal?

Ok, there is Keyboard function priority list disproving my assumption of consistency, but still it would be easier to make an aircraft specific switch statement in Nasal to call a key assignment then reading the aircraft model of what to call.

[Johan G]

Some posts regarding keyboard bindings related to the generic autopilot was moved to the topic Looking for aircraft with 'paper cut' bugs

[Philosopher]

To execute a key there's a couple steps involved (I recall doing this once... I don't know if I still have the code):

• find the value of the key. Might as well use character constants (backquotes) like this: `a`
• find the node in the property tree. I forgot specifics, but its something like /input/keyboard/key[i]/
• find the binding. This can be key[i]/binding, or key[i]/mod-up/binding, mod-shift, etc. etc. (again, fuzzy on the details sorry)
• execute the binding! see props.nas, specifically props.runBinding of course

HTH

[vanosten]

So an example would be like follows.

Using the magnificient Viggen you find the keybindings in fgaddon/Aircraft/JA37/ja37-input.xml.

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      <key n="93">
         <name>]</name>
         <desc>Increase radar range</desc>
         <repeatable>true</repeatable>
         <binding>
                <command>property-cycle</command>
                <property>/instrumentation/radar/range</property>
                <value type="int">15000</value>
                ...


Then in the joystick specific xml:

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  <button n="12">
    <desc>Increase Radar Range</desc>
    <repeatable>false</repeatable>
    <binding>
      <command>nasal</command>
      <script>props.runBinding(props.getNode('/input/keyboard/key[93]/binding'))</script>
    </binding>
  </button>