Afterburner flameout question

[TLTeo]

Currently, if the AB flames out at high altitude, there is no way to get it to re-ignite (at least, none that I can find). Going back to lower altitudes does not seem to help. Should this be happening?

[outbaxx]

Afterburner flameout question

 

No it should not.

It shouldn’t flameout at high altitude if you fly fast and you should be able to re-ignite.

There are some limits for igniting the afterburner and the different AB zones but the limit that is modeled now is not correct.

 

http:// https://forums.eagle.ru/showthread.php?t=254364

 

It’s never too late to give up

Edited December 4, 2019 by outbaxx

[QuiGon]

As outbaxx said: It's one of the long standing Viggen bugs waiting for a fix since forever: https://forums.eagle.ru/showthread.php?t=220786

 

If you ask me it looks like it's another bug that the devs have forgotten about, which could be prevent with a community bug tracker IMHO...

At least I don't think this bug is too hard to fix, as it just looks like they forget to set reset a single boolean.

Edited December 5, 2019 by QuiGon

[RagnarDa]

Afterburner flameout question

 

Not forgotten just down-prioritized

 

Edit: I have looked into it but couldn’t find what the issue was and had to divert my attention elsewhere

Edited December 5, 2019 by RagnarDa

[outbaxx]

 

The problem is that it’s not modeled correctly.

 

Blue zone: outside envelope, above 18aoa probably.

 

Red zone:

AB zone3 will flameout, AB won’t ignite and re-ignite.

AB zone 1-2 don’t work

 

Yellow zone:

AB zone3 works but AB will not ignite/re-ignite.

AB zone 1-2 don’t work

 

Green zone:

AB zone 1-3 work

 

 

 

It’s never too late to give up

[RagnarDa]

Afterburner flameout question

 

That’s not what I meant. I was referring to not being able to fix it.

 

Edit: I realize I was unclear.

Edited December 5, 2019 by RagnarDa

[TLTeo]

Why would the AB not re-ignite when going back to lower alt and speeds though (Say, Mach ~0.9 at 10km)?

[RagnarDa]

Because it’s a bug

[RagnarDa]

Found the issue I believe and fixed it. Needs to do some manual testing and then hopefully it will make it into a patch soonish... Thanks for the reports!

[RagnarDa]

Verified working. I don't know exactly what patch it will be in, probably not this week at least.

[Skyracer]

Currently, if the AB flames out at high altitude, there is no way to get it to re-ignite (at least, none that I can find). Going back to lower altitudes does not seem to help. Should this be happening?

 

Before the last update you where able to solve this. By moving the throttle to idle and than to WOT at lower altitudes.

[TLTeo]

Yay!

[TOViper]

I sometimes also managed to solve this problem using this strategy.

But IRC this was long time ago, I think it even was in versions 2.5.3 or below.

 

 

Knowing about this issue when flying newer DCS versions, I stopped AB at 13500m in order to avoid it (some kind of "normal DCS Viggen procedure") :D.

[RagnarDa]

The issue was that the ignition would not start unless in a specific low RPM range. Also automatic reignition doesn’t start unless the RPM is lower than a threshold. If the turbine is still working and only the AB flame is out the ignition would almost never start. So I figured the AB might be relit just by ambient temp in the engine and sufficient fuel flow.

[Skyracer]

The issue was that the ignition would not start unless in a specific low RPM range. Also automatic reignition doesn’t start unless the RPM is lower than a threshold. If the turbine is still working and only the AB flame is out the ignition would almost never start. So I figured the AB might be relit just by ambient temp in the engine and sufficient fuel flow.

 

How about solving the engine återstart/relight function?

[outbaxx]

Afterburner flameout question

 

The issue was that the ignition would not start unless in a specific low RPM range. Also automatic reignition doesn’t start unless the RPM is lower than a threshold. If the turbine is still working and only the AB flame is out the ignition would almost never start. So I figured the AB might be relit just by ambient temp in the engine and sufficient fuel flow.

 

 

The AB won’t relit unless you set the throttle in MIL power first, there is no automatic relit of the afterburner.

If you are in Z2 or 3 (when it light out) there is a valve that close the fuel to the regulator so it doesn’t pump/Compressor stalls but if your in Z1 the valve won’t close and there can be a compressor stall and there is a high reduction in thrust.

The throttle need to go back to Mil power before a new ignition will work.

Edited December 12, 2019 by outbaxx

[RagnarDa]

So not quite right yet then but it works for now hehe

[outbaxx]

So not quite right yet then but it works for now hehe

 

 

A step forward is always a step forward :)

[RagnarDa]

It’s a demotion of the issue severity level at least

[randomTOTEN]

So I figured the AB might be relit just by ambient temp in the engine and sufficient fuel flow.

I don't know for sure how the RM8 (JT8D-1) afterburner works, but just going from a "general concept" perspective, there should be an independent afterburner igniter which ignites the afterburner fuel spray.

 

 

Here is the relevant unit for the J79

 

 

 

 

I wouldn't be surprised to learn there is one in the RM8.:book:

Edited December 15, 2019 by randomTOTEN
embed doesn't work

[TOViper]

So not quite right yet then but it works for now hehe

 

RagnarDa, quick question: is this patch already implemented?

Today I was flying, turned off the AB at approx 14000 m, went for 20000 m in mil thrust, came back and the AB was not igniting anymore at 4000 m.

[MYSE1234]

RagnarDa, quick question: is this patch already implemented?

Today I was flying, turned off the AB at approx 14000 m, went for 20000 m in mil thrust, came back and the AB was not igniting anymore at 4000 m.

 

It should be in, I had it work a few days ago.

[TOViper]

It should be in, I had it work a few days ago.

 

 

Definitely didn't work here at Openbeta 2.5.5.41962