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Afterburner delay and fails?


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In the F-5 there is something I find very annoying, the afterburner seems to have a very important delay between the moment you push the throttle to max and the moment the AB kicks in (no matter if from iddle to mil power)...it takes more or less 4 seconds!!:huh: this is a hell of a lot of time...so in this plane I need to anticipate too much to moments in which I migh need it and some times those 4/5 secs are very important, for example in a merge...

 

Another thing I experience is that sometimes, for no reason apparently, the right engine doesnt activate AB even when I have the throttle at full power :huh: ...I remember that it always happens with the right engine and its NOT a problem with the controls nor the hotas because I see using control+enter that the power is at FULL in both engines. So I have to pull the throttle back a bit and then at full and the AB kicks in finally.

 

Some times I have had problems in dogfights because the right engine wasnt giving me the AB power and I notice it many times when its too late to react looking at the rpm gauge and seeing its not at AB level...

 

This post is to find out if this is how the plane behaves IRL or if there is some problem regarding this. Are you guys experiencig this also??

 

cheers!!:thumbup:

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Also noticed that delay but seems to me more natural for the engines to behave like that than instantly going on AB. Don't know if u noticed that if you push the throttle fast for full AB the RPM idling a bit to >90 then going up again but if you slowly advance the throttle RPM are maxing normally to AB power. Seems to me very realistic.

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thanks for the reply!!

 

while I understand what you mean with realistic feeling (things dont use to be instant IRL) also think about F-15, mig-29, Su-27, etc. where the AB only takes 1 sec or so. I never piloted any of those planes (sadly :P ) but Im pretty sure this is how they behave IRL so slower AB doesnt necessarily mean more realistic feeling.

 

Anyway, I guess this is how the real plane works but just wanted to be sure of it and share with you guys this regard.

 

What I find really weird is the problem of the right engine AB not working some times...I cant manage to identify any reason for that...some times it works perfect, others I push to full power and after a while I realize my right engine's rpm are not as they should at full AB as well as nozzle position, temp, etc. so it looks like something working coherently but at the same time oddly...

 

I dont think RL F-5 pilots have to deal with engine AB not working some times right?...and its not happening after a long time of inverted flight, or high g's, etc....no, after flying straight, right into a merge, I push to full power and sometimes bang!!, right engine fails to kick AB which I notice too late because I was trying to keep sight of the enemy plane Im dogfighting :doh: ...

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Actually what you are describing is very close to how it is in reality and as is described in T.O. 1F-5E-1 - Flight Manual regarding engine operation.

Check it out if you can and you will see how close BST is with engine modeling to real thing. They did amazing job on F-5.

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I don't know about the right engine thing, but I do know aircraft engines at that time frame had the delay when setting afterburner. Whether it was 4 seconds or not I don't know, but I remember reading of a pilot in Vietnam who found himself sinking towards the ground after a bomb run (f105 I think) who crashed because he selected afterburner and lost some crucial thrust before it caught. I think afterburners work different now. I think it basically "choked" the engine for a few seconds with extra fuel until it lit.

 

 

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thanks mates, I think the "delay" issue is solved then...as I though I guess its a matter of technology, and that time fighters simply had a slower AB system, and yeah, BST did and AMZING job with all the F-5 module!!

 

But the problem with the AB failing some times is the worst thing...I havent had this issue with any other plane never, it happens in 1.5 and other 3 differents installs of the 2.0 version I have, my warthog is like 3 months old and works great and I remember having this issue also with my old X52 pro so...anyone elese has ever experienced this particular issue??


Edited by watermanpc

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But the problem with the AB failing some times is the worst thing...I havent had this issue with any other plane never, it happens in 1.5 and other 3 differents installs of the 2.0 version I have, my warthog is like 3 months old and works great and I remember having this issue also with my old X52 pro so...anyone elese has ever experienced this particular issue??

 

Yes. This is also pretty standard behaviour for an aircraft of the F-5s generation, it's simply the AB failing to light off. (the fact that the fuel flow stays at AB levels is questionable, but that might just be due to the way AB light failures/blowouts are modelled).

 

Unlike modern fighters the engines in the F-5 don't have any digital control/management systems, so if you start slamming the throttles around and/or making large power setting changes at high AoA/low speed you can expect to see issues such as surges, stall, and AB light off issues.

 

To minimise AB light off issues in the F-5 allow the engines to stabilise at max dry before engaging AB. Even doing that you may still see the odd light off failure at low airspeed, high AoA, and high altitude.

 

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Great to know, thanks for the info :thumbup:

 

Anyway, I have a couple of questions more:

 

1- If I remember correctly, I have had the issue even after being a few minutes at high power level, so after the engines being stabilized, in fact I would say that most of the times I have had the problem have been seconds before the merge so flying straight and at high/mil power.

 

2- why only the right engine?...I dont remember this happening to the left one...is that also normal and how it is supposed to behave?

 

thanks for your help!

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Real J85 engine behavior in a T-38A:

 

 

Yes, it's a slightly different variant, but the behavior (spool time, nozzle position and scheduling, oil pressure, RPM, EGT, FF, etc) is representative of the entire (after burning) J85 family.

 

You can draw your own conclusions re: the current modeling.


Edited by FNU LNU
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The AB not lighting up has been discussed and reported several times:

 

https://forums.eagle.ru/showthread.php?t=172526

https://forums.eagle.ru/showthread.php?t=171851

 

I thought it was a feature, but in the second thread Skatezilla states that developers asked for a track and it was provided, what makes me think that this "feature" was unknown to them, making it more like a bug. Here:

https://forums.eagle.ru/showpost.php?p=2866511&postcount=8

 

Anyway, I have not found an official statement about it and I cannot seem to be able to reproduce it at will or find a method to completely avoid it.

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The following factors will reduce the probability of a successful afterburner lightoff - combined, they can make it very difficult or impossible.

 

Low airspeed

High altitude

High Angle of attack

High sideslip angle

Rapid throttle movement

 

The F-5s engines are quite picky. The most reliable way to ensure afterburner lightoff has occurred is the nozzle position indicators. If either one fails to swing through the 6 o'clock position (stays closed), then that afterburner hasn't lit. Biskly moving the throttle back to full MIL, then to afterburner should fix the problem. If not, then you're probably near the edges of the afterburner lightoff envelope.

DCS modules are built up to a spec, not down to a schedule.

 

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yeah, the nozzle position the what I use to know if the AB is enabled or not. As you said, I have to move back the throttle to a non-AB position and then all the way in to try a second time and the AB finally kicks in...

 

Maybe what I do wrong is sometimes rapid throttle movements which is in your list so I will have to keep an eye on that.

 

Thanks for your help!

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