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Transponder: Difference between revisions
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== Id Codes == | == Id Codes == | ||
Id or 'squawk' codes aid ATC in identify aircraft positively. 1200 is the standard code for VFR flight, IFR aircraft will typically be advised a code on delivery clearance or startup. | Id or 'squawk' codes aid ATC in identify aircraft positively. 1200 is the standard code for VFR flight, IFR aircraft will typically be advised a code on delivery clearance or startup. | ||
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== Modes == | == Modes == | ||
See [http://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes Aviation transponder interrogation modes] (Wikipedia) for official description. Civilian Mode-S and Mode-C both transmit pressure altitude (at 10-foot and 100-foot precision, respectively). To do this the transponder needs an altitude source. In real-life this can be a separate box called an encoder, or may be derived for FMC / ADIRU sources. It's important to note this altitude is referenced to standard pressure (29.92 inHg / 1012Hpa), and not corrected for actual barometric pressure in the local environment. | See [http://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes Aviation transponder interrogation modes] (Wikipedia) for official description. Civilian Mode-S and Mode-C both transmit pressure altitude (at 10-foot and 100-foot precision, respectively). To do this the transponder needs an altitude source. In real-life this can be a separate box called an encoder, or may be derived for FMC / ADIRU sources. It's important to note this altitude is referenced to standard pressure (29.92 inHg / 1012Hpa), and not corrected for actual barometric pressure in the local environment. | ||
Additional support for military modes is possible if anyone wishes to add it. | Additional support for military modes is possible if anyone wishes to add it. | ||
== Configuration in | == Configuration in FlightGear == | ||
Transponder support was overhauled in May 2013; earlier versions (2.10 and prior) have different support and are not documented here. Updating an aircraft to use the new config is straightforward. Key transponder properties (altitude, ident and transmitted-id) are now sent via the MP protocols for use in ATC clients. | Transponder support was overhauled in May 2013; earlier versions (2.10 and prior) have different support and are not documented here. Updating an aircraft to use the new config is straightforward. Key transponder properties (altitude, ident and transmitted-id) are now sent via the MP protocols for use in ATC clients. | ||
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=== Run-time properties === | === Run-time properties === | ||
* '''altitude''': gives the transmitted altitude in feet (or -9999 for invalid) | * '''altitude''': gives the transmitted altitude in feet (or -9999 for invalid) | ||
* '''altitude-valid''': indicates if altitude value is valid data or not | * '''altitude-valid''': indicates if altitude value is valid data or not | ||
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* '''transmitted-id''': gives the value being transmitted, including over the network via MP | * '''transmitted-id''': gives the value being transmitted, including over the network via MP | ||
====Input properties==== | ==== Input properties ==== | ||
These live under <tt>/inputs</tt>. | These live under <tt>/inputs</tt>. | ||
* '''knob-mode''': sets the transponder operating mode. This corresponds to the KT-70 knob positions for convenience, but the actual modes should work for any transponder instrument. Knob modes are documented below | * '''knob-mode''': sets the transponder operating mode. This corresponds to the KT-70 knob positions for convenience, but the actual modes should work for any transponder instrument. Knob modes are documented below | ||
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In KT-70 compatibility mode, additional properties are read and set, to preserve legacy aircraft. Do not use these properties in new aircraft. | In KT-70 compatibility mode, additional properties are read and set, to preserve legacy aircraft. Do not use these properties in new aircraft. | ||
====Knob/Functional Modes==== | ==== Knob/Functional Modes ==== | ||
* 0 - off | * 0 - off | ||
* 1 - standby, basically the same as off for the C++ code (3D instrument would power up the display, presumably) | * 1 - standby, basically the same as off for the C++ code (3D instrument would power up the display, presumably) | ||
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* 4 - On, normal operation but altitude transmission is inhibited | * 4 - On, normal operation but altitude transmission is inhibited | ||
* 5 - Alt, same as on but altitude is broadcast if transponder was configured in Mode-S or Mode-C | * 5 - Alt, same as on but altitude is broadcast if transponder was configured in Mode-S or Mode-C | ||
=== Generic transponder === | === Generic transponder === | ||
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</transponder> | </transponder> | ||
</syntaxhighlight> | </syntaxhighlight> | ||
== Related content == | |||
=== Wiki articles === | |||
* [[Howto:Develop an aircraft transponder in Nasal]] – Most probably obsolete | |||
* [[Multiplayer protocol]] – The IDs 1501-1503 are earmarked for transmitting transponder properties | |||
* [[OpenRadar: Transponder]] | |||
=== Forum topics === | |||
* [https://forum.flightgear.org/viewtopic.php?f=4&t=6395 Transponder] (Nov 2009-Dec 2010) | |||
* [https://forum.flightgear.org/viewtopic.php?f=75&t=19826 Transponder over network] (Apr-Jul 2013) | |||
* [https://forum.flightgear.org/viewtopic.php?f=4&t=31492 Transponder properties over MP] | |||
=== Source code === | |||
* {{flightgear source|src/Instrumentation/transponder.hxx}} | |||
* {{flightgear source|src/Instrumentation/transponder.cxx}} | |||
[[Category:Aircraft enhancement]] | [[Category:Aircraft enhancement]] | ||
[[Category:Aircraft instruments]] | [[Category:Aircraft instruments]] | ||