Afterburner detent ( percentage of throttle when it engages) does not match controls indicator

[darkman222]

I am recently configuring my physical afterburner detent and I double check between external view and the controls indicator (RCTL +Enter) and realized that although I am right above the threshold for afterburner according to the contols indicator the after burner seem to engage with a much higher throttle setting.

Significantly above the AB threshold but no AB engaged

The depicted throttle setting is the threshold where it engages. In percentages speaking. The shown threshold in the controls indicator is at exactly 75% like in the F16. But in the F18 it engages with 82 %.

 

For illustration an example from the F16

Afterburner already slightly lit

Is the controls indicator wrong or am I missing something?

The controls indicator is showing the position the AB engages correctly in all the other modules (F14, F15 SE...)

 

 

Edited December 3, 2023 by darkman222

[virgo47]

The AB position on the throttle is different for various planes. The info I use is from this post:

Both modules you mentioned use AB detent on 80% of the throttle. F/A-18C states 74 in the table - although I personally use 75% as I don't see any spike in the fuel flow there yet.

Now you have two options:

1. Create a different detent HW setup if you can - e.g. with STECS throttle.
2. Change the throttle curve.

I use a single bracket for all AB planes (at least for now), I set it up with F/A-18C by some luck, so I don't need any curve there. But for other planes (F-15C, F-5E, Mig-29) I need it.

I switch the throttle to Slider (1), often need to check Invert (2) too, and set the Curvature (3), so that the Output (4) shows the number from the table above (-80 for F-15C 20/80). If it is just a bit less, then your max military power without AB is a tad lower, if it's more, than you're in AB before the detent. The curvature is not super granular, it probably can be set more exact in the Lua config file, but let's not go there. I'm happy with curvature.

Note that planes with higher AB than your HW setup will have inverse curve (e.g. Mig-29 has positive 14 in my case).

I set one throttle on dual engine, test it in cockpit, move it one more/less as I fancy, check that AB stage sound (prominent with F-15C) really goes when I move over the detent - and when I'm happy I set the other engine the same way. Double check it, just in case your HW is not totally symmetric.

The question is WHERE should your HW detent be. One can push it towards the end a bit, but then you just "turn it on" and barely have enough room to enjoy all the stages (e.g. 5 in F-15C). I'm fine with 75% on my STECS (the detent physically starts around mark 80 and ends around mark 90, but 80 is not 80% because of the stop/idle detent). There is a small, but still sufficient room if I want to fine-tune the AB power.

As a side note, I use detent for engine stop/idle and add just a bit of deadzone for that area, to be really idle with some tolerance.

[darkman222]

Well first of all, thanks for the detailed post. I used the same method with the spreadsheet mentioned above for all my aircraft in DCS. Which are quite a lot.

But the main question seems to be adressed here:

3 hours ago, virgo47 said:

although I personally use 75% as I don't see any spike in the fuel flow there yet.

What youre saying is that you believe in 75% as the point where the AB engages although the visual representation is at 82% thrust set by hardware. That means that you determine the AB position by checking the fuel flow but not the visual representation of the AB flames.

If you say the fuel flow spikes above 75% then the control indicator is correct but the visual representation of the AB in the F18 is broken. I dont believe that if the AB engages at 75% will become only visible from the outside at above 82% ? The only possible answer is that it possibly burns without a visible flame up to 82% throttle position which I think is not plausible.

Edited December 4, 2023 by darkman222

[virgo47]

1 hour ago, darkman222 said:

What youre saying is that you believe in 75% as the point where the AB engages although the visual representation is at 82% thrust set by hardware. That means that you determine the AB position by checking the fuel flow but not the visual representation of the AB flames.

If you say the fuel flow spikes above 75% then the control indicator is correct but the visual representation of the AB in the F18 is broken. I dont believe that if the AB engages at 75% will become only visible from the outside at above 82% ? The only possible answer is that it possibly burns without a visible flame up to 82% throttle position which I think is not plausible.

Jeez, perhaps I read all your post wrong from the start. I focused on the F/A-18C vs other planes difference... Silly me.

So the question is: Does F/A-18 AB really start at 74-75%? Isn't it more like 82% of the throttle?

I don't know really. What I can confirm is that around 75% it looks like this in the cockpit:

On the outside, the nozzles just started to open and there is NOT a flame visible. The flame comes out around 82-83% indeed, and the cockpit reads:

Just a slightly lower throttle cuts the flames and FF drops to <140, and then it drops quite quickly all the way to the 75%, from there lower the FF change seems to be slower and slower.

So it SEEMS the marked detent on 75% for F/A-18C (and also widely repeated in the users' research) does not match the flame at least. We can agree on that.

But I'm no SME on the topic. The nozzle starts to open sooner, the flame comes later... perhaps the first AB stage does not produce any visible flame?

So sorry for jumping in with an explanation for a no-problem and let's wait for answers from experts.

[darkman222]

Not really sure about the fuel flow as indication when AB starts. At least the nozzle does not move any more when going over the 75% percent which could be a sign that AB engages.

It seems like there is more signs that AB engages over 75% than that its not engaging.

Unless someone has better information, I assume that the 75% position is the correct AB position but the flame animation starts at 82%. Which cold be a bug or maybe it really is burning without a visible flame in that lower setting.

Edited December 6, 2023 by darkman222

[Razor18]

Check whether you have "AB detent - always off" in the Options/Special tab F-18? Thats how it supposed to be, otherwise you need to press the detent keybind every time to engage AB.

[Joch1955]

I have not had any issues or noticed anything unusual with the F18 compared to other DCS planes.

Easiest way to check when the AB comes ON/OFF is with external view. On my throttle (Orion 2), that corresponds to 80% of travel. I have mine setup so I hit 100% MIL power when it gets to the AB detent. Works flawlessly.

All the tools are there, you just have to take the time to set it up properly.

[darkman222]

Sure you can set it up with a lots of different tools. Even with the external winwing software I can set the AB detent if I don't wanna use DCS curves.

But the initial question was where the AB engages.

Using fuel flow as indicator it's 75 %

Using external view and visual representation , the AB flames, it's at 82%

[Razor18]

What is your experience, what is the fuel flow figure just before AB engages? Just curious why the difference between the two methods?

To make it a bit more complicated, I have slightly different values just before the AB lights up (with the throttle going up) compared to when AB flame extinguishes (pulling it back out of burner).

For me it seemed like at the point when you (going up) have reached the RPM% 100, the fuel flow is also about 100 lbs/h (meaning 10000 of course). If you push up more, FF jumps way up, but when you pull it back from that point, the reduction of FF is rather linear, which for me tells it is about the sweet spot. Just my 2 cent, not arguing.

Edited January 2, 2024 by Razor18

[darkman222]

As I wrote. There are more indication that the AB starts engaging at 75 or rather 76% as documents from the Internet state.

Another thing that came to my mind was if the flame animation is wrong. Could be a thing on multiplayer if you don't see your flight lead engage the AB while flying formation.

Maybe a moderator can demystify @BIGNEWY ?!