Spoken GCA: Difference between revisions

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Correct your vertical speed if you hear ''"<Above/Below> glidepath."''
Correct your vertical speed if you hear ''"<Above/Below> glidepath."''
= How control.nas script works =
= How control.nas script works =
[[File:Gca schema.png|right|This is the general (simplified) scheme of the gca module:<ref>{{cite web  |url    =  https://forum.flightgear.org/viewtopic.php?p=319409#p319409  |title  =  <nowiki> Re: Spoken GCA </nowiki>  |author =  <nowiki> rleibner </nowiki>  |date  =  Sep 26th, 2017  |added  =  Sep 26th, 2017  |script_version = 0.40  }}</ref>]]
The ''gca.Control()'' function instances a "demo" object from ''gca_class'' and sets aircraft and destination values. <br />
The ''gca.Control()'' function instances a "demo" object from ''gca_class'' and sets aircraft and destination values. <br />
It also instances a "Par" object from ''PARScreen_class'' to track the aircraft on the PAR screen.<br />
It also instances a "Par" object from ''PARScreen_class'' to track the aircraft on the PAR screen.<br />

Revision as of 17:14, 26 September 2017

rleibner and hooray are working on an Spoken GCA script, and it's time to share with you the beta version.

WIP.png Work in progress
This article or section will be worked on in the upcoming hours or days.
Note: Although still incomplete, the information it contains is valid and available.
See history for the latest developments.
Screenshot showing rleibner's GCA/PAR screen (Canvas based) in conjunction with a Canvas driven GUI dialog to configure the GCA [1]

Spoken GCA allows the pilot to listen to the directives of the Ground Controlled Approach. (see Howto:Implementing_a_simple_GCA_system)

Background

Cquote1.png Is there any work on GCA (ground controlled approach) in progress, or have missed it? GCA is surprisingly accurate and easy to use, both as a pilot and a controller.
— Alant (Sun Ago 13). Re: Spoken ATC.
(powered by Instant-Cquotes)
Cquote2.png

What GCA is

What can you expect from GCA

Horizontal trajectory when pilot follows GCA instructions
Vertical trajectory when pilot follows GCA instructions

Arriving in the vicinity of the airport with little or no visibility, the pilot can request the GCA service.

The Controller, assisted by a PAR (Precision Approach Radar), will guide you through a safe path (both in heading and in altitude) that will take you to the head of the used runway.

How to install

Note  This is the latest version (Sep 20, 2017) including PARscreen autozoom.

If your FGFS version accepts Addons, you can download this feature from (not uploaded yet). Read the directions as a reference.

Otherwise, follow this:

  1. - Download the Spoken_GCA.zip. There you will find a "gca.nas" file and a "Gca" directory with 7 files inside.
  2. - Extract all into the $FG_HOME/Nasal directory (keeping the directory structure !).
  3. - Edit the $FG_ROOT/keyboard.xml file and include the following lines in order to bind [2] the ">" key:
    <key n="62">
        <name>greater-than</name>
        <desc>Spoken GCA</desc>
        <binding>
        <command>nasal</command>
        <script><![CDATA[
              gca.Control();
              ]]>
        </script>
        </binding>
    </key>

And that's all !
If you prefer, you can bind an unused joystick button too.

How to use it

When you are about 10 or 15 miles from your destination, tune Comm1 to an available ATC frequency (you can find them at Menu/Location/Airfield information), and press the ">" key to request GCA assistance.
You will hear the GCA's answer "<callsign>, this will be a PAR approach to <airport> runway <rwy>."

Depending on your position and altitude, it will give you a vector towards the base leg or towards the final one. Also will instruct to climb or descend if necessary.
Follow closely those instructions making standard turns first, and half standard ones when indicated. Adopt about 90 to 110 kts IAS until you hear "Begin descent", and configure a "final" atitude then.
If you are adviced "<Well/Slightly> <left/right> of course." then make "S" turns to fix that. Little ones if "Slightly", big ones if "Well".
Correct your vertical speed if you hear "<Above/Below> glidepath."

How control.nas script works

This is the general (simplified) scheme of the gca module:[3]

The gca.Control() function instances a "demo" object from gca_class and sets aircraft and destination values.
It also instances a "Par" object from PARScreen_class to track the aircraft on the PAR screen.

Each second, the script receives an instruction. But it is neither possible nor convenient to pass these instructions to the pilot every second !
So it checks the demo.phrase and demo.maxsecs members. (demo.phrase is not the instruction itself, but the "instruction-type". And demo.maxsecs is the maximum elapsed time between consecutive "spoken" instructions.)
If the received demo.phrase is the same as the previous one, the script waits <demo.maxsecs> seconds before instruct the pilot.
But if demo.phrase changes, then the pilot will be instructed immediately.
(To be continued . . . )


References

References