Afterburner modulation

[Obic]

I ran a few intercept practice the other day & going high Mach number would result in a flame out. (Everything normal here)
But Unlike the Mig-21, I cannot modulate the Afterburner to avoid exceeding critical Mach
Despite the large throttle movement visually, the thrust seems to remain the same when the AB is on. (Ctrl+Enter was on)

Did I miss something in the manual or it`s a On/Off type of afterburner deal
Thank you 

[Bremspropeller]

That's a great question about a topic I've been wondering about a lot, too.

The engine schematics and description say there's three burner-rings, but they're all fed through a common fuel-manifold. There's a second ring (?) upstream, fed by a different manifold, but I haven't seen a description of what it does and how it works. It's provided by the same pressure regulator, through.

Normally, multiple rings indicate multiple burner stages, but it seems they're all fed by a common manifold, so they'd be coming on/off simultaneously.

Maybe the fuel is metered altogether instead of adding or isolating rings.

Edited September 2, 2023 by Bremspropeller

[gulredrel]

1 hour ago, Obic said:

I ran a few intercept practice the other day & going high Mach number would result in a flame out. (Everything normal here)
But Unlike the Mig-21, I cannot modulate the Afterburner to avoid exceeding critical Mach
Despite the large throttle movement visually, the thrust seems to remain the same when the AB is on. (Ctrl+Enter was on)

Did I miss something in the manual or it`s a On/Off type of afterburner deal
Thank you 

Do you mean the large movement on your desktop throttle? You can adjust the AB detent position in plane's special options menu. I think, I've mine set to 90%. Once you hear the click in the cockpit from the detent, it's like AB on or off. No modulation.

[fausete]

The afterburner throttle position does indeed affect thrust significantly. You can check it on the ground by setting the parking brake. In minimum afterburner, the brake will be able to hold the plane in place but not in maximum afterburner.

The next OB update will include some tweaks to supersonic drag that might affect the situation you describe. Something to consider too is that, in supersonic regimes, thrust will generally always increase with speed.

Edited September 2, 2023 by fausete

[Bremspropeller]

17 minutes ago, fausete said:

The afterburner throttle position does indeed affect thrust significantly. You can check it on the ground by setting the parking brake. In minimum afterburner, the brake will be able to hold the plane in place but not in maximum afterburner.

Thanks forth quick answer!

Could you give a short explanation how the modulation does work?

[fausete]

Hi again @Bremspropeller,

So the regulation is through control of the fuel flow to the AB as a function of power setting and engine limitations.

[Obic]

Thank you for the quick reply 

It's been a month so maybe I missed something
I'll give it a shot as soon as I come back home in a week