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What does this switch?


Jagdgeschwader

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Hi. 

Maybe I missed something but I've searched in the manual about this switch and I found nothing about it.

I didn't notice any changes when I switch it to MAN or AUT during startup or during flight.

Does anyone know what it does and what's the purpose of this switch?

Here's a screenshot of it:

Inked31-0_LI.jpg

Viggen GIF 2.gif

"If we don't end war, war will end us."  

H. G. Wells

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7 minutes ago, Jagdgeschwader said:

Ok thanks anyway😃 I will try to find it in the original AJS 37 Viggen manual, maybe there is some info about it.

Del 1, Flik 9 - Sida 32-33. 🙂

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When relay R2 turns on, the ignition boxes and the ignition system lamp field are in the AUT position 
and the ignition switch is in the ON position (locked with locking wires in the respective positions).
The spark plugs ignite the fuel/air mixture in the gas generator flame tube and the gas generator 
continues to accelerate.
If the extinction sensor malfunctions so that it unnecessarily energises the ignition boxes
(the ignition system light is on continuously for a long time), it can be disconnected by setting the
ignition system switch to MAN and relay R4 will pull. 
The ignition system switch is then held in this position by relay R3.
Timer switches off after about 60s, at which point the power to the ignition boxes and lamp field is cut off 
and the restart procedure stops.
If the ignition switch has been set to MAN position 
(extinguishing sensor disconnected) before the restart is initiated, 
it will automatically spring back to AUT position, by relay R3 becoming de-energised 
when the restart button is pressed.
At gas generator speeds below 51%, restart can also be initiated manually with the START switch, 
which means, among other things, that the GTS is started. However, at GM rpm above 47%,
no self-hold is obtained on the START switch. 
Attempting to restart with the START switch at GM rpm above 51%
causes an overspeed relay to cut power to the GTS for the rest of the flight.

------------------------------------------------------------------------------------------------------------------

This is the part I was able to translate (hopefully correctly), but it's veeeery difficult to understand.

Sorry if the translation is not very accurate😅 


Edited by Jagdgeschwader

Viggen GIF 2.gif

"If we don't end war, war will end us."  

H. G. Wells

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On 2/23/2022 at 2:46 PM, Jagdgeschwader said:

Thanks I know that it is for ignition but in which case should I switch it to MAN then?

 

You basically shouldn't. In the real aircraft there's even a thin lock wire keeping it in the AUT position, which should tell you what level of "don't mess with this" it's on.

The specific (and rare) fault condition the switch is supposed to be used for has to do with the automatic engine restart system. There's a flameout detector in the combustion chamber, and if that trips, the engine ignition system is turned on in order to try to restart the engine. This is accompanied by a master warning and the lamp TÄNDSYST on the annunciatior panel (it remains lit as long as the ignition system is on). If the flameout detector is faulty and gets short-circuited so it's permanently tripped, then the ignition system is on all the time, which is obviously undesirable. You can disable the flameout detector (and the automatic re-ignition) by flipping the TÄNDSYSTEM switch to MAN. If you then try to manually restart the engine with the ÅTERSTART switch, the TÄNDSYSTEM switch automatically flips back to AUT.

I have no idea if a faulty flameout detector is a thing that DCS can simulate, but there you go, that's what it's for.


Edited by renhanxue
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vor 36 Minuten schrieb renhanxue:

You basically shouldn't. In the real aircraft there's even a thin lock wire keeping it in the AUT position, which should tell you what level of "don't mess with this" it's on.

The specific (and rare) fault condition the switch is supposed to be used for has to do with the automatic engine restart system. There's a flameout detector in the combustion chamber, and if that trips, the engine ignition system is turned on in order to try to restart the engine. This is accompanied by a master warning and the lamp TÄNDSYST on the annunciatior panel (it remains lit as long as the ignition system is on, even if you acknowledge the warning). If the flameout sensor is faulty and constantly sending a flameout signal, then the ignition system is on all the time, which is obviously undesirable. You can disable the flameout sensor (and the automatic re-ignition) by flipping the TÄNDSYSTEM switch to MAN. If you then try to manually restart the engine with the ÅTERSTART switch, the TÄNDSYSTEM switch automatically flips back to AUT.

I have no idea if a faulty flameout detector is a thing that DCS can simulate, but there you go, that's what it's for.

 

Wow, thanks for the explanation! Now I understand what this is for 😃

Viggen GIF 2.gif

"If we don't end war, war will end us."  

H. G. Wells

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