Mirage 2000 Fuel flow

I have a new question regarding the subject.

In the current state of the module, Mirage is consuming ~90 kg/min at full mil on the ground (take off).

But as it gets airborne, it starts consuming more, even with the altitude increasing. It's becoming more economic only above ~4k ft (my estimation). Like, when you're on the deck @ full mil, you're gettin 112-120 kg/min... I'll provide screenshots later if needed

is this how it's supposed to be ?

I have a new question regarding the subject.

In the current state of the module, Mirage is consuming ~90 kg/min at full mil on the ground (take off).

But as it gets airborne, it starts consuming more, even with the altitude increasing. It's becoming more economic only above ~4k ft (my estimation). Like, when you're on the deck @ full mil, you're gettin 112-120 kg/min... I'll provide screenshots later if needed

 

 

is this how it's supposed to be ?

The fuel consumption and speed relations are quite wrong in the M-2000C. Your fuel flow (FF) will increase with forward speed, due to ram effect. The engine needs to compensate for the incoming air, which doesn't necessarily mean you're making more thrust, in fact it's quite the opposite until certain speeds depending on inlet system. For colder temperatures, the engine has to trim/adjust the fuel flow because the turbine requires more horsepower to drive the compressor, so the fuel flow is increased.

But as I said, your fuel consumption will always increase with speed, it should decrease with altitude due to the air inlet density decreasing. However, the fuel flow and speed relations aren't correct, the FF should be greater at high speeds.

I was flying at 924 kts at 35,000 ft with a FF of 174 kg/m, this number should be twice I believe, again I don't have any docs on the M53 engine, I'm just guessing here but it should be much, much higher.

And little detail that proves the Mach and FF relation are wrong, this number stayed the same from 600 kts until 900 (Over Mach 2.1).

oh ok, thanks for the knowledge !

oh ok, thanks for the knowledge !

No problem, again I don't have any charts showing what I said above, but that's how turbojets and turbofans behave, generally speaking. But you can take a look at the F-15 and see how the FF varies. You can pretty much apply that to the M-2000C, except the fuel flow number, but the way it varies should be similar.

It is ram air effect that makes a modern jet that much more efficient compared to an older propeller driven airplane.

The higher we fly the thinner the air the less the drag the more efficient we can fly fast. (Up to the limit where a subsonic plane would stall even it is flying vne - the coffin corner speed)

But - to burn fuel you need the oxygen out of the air which is of course the less the higher you fly. This is why the piston engine becomes so ineffective. You do need additional turbocharger or compressors to get enough air into the cylinder together with the fuel you want to burn.

The jet engine get's a huge bonus coz it's compressor gets ram air compressed 'for free' to 'breath' - the faster the jet flies the higher the ram air effect! This compensates 'to a degree' the problem of the thin air up high.

The fuel flow is acting very, very strangely and needs to be looked at throughout the envelope - in climbs, acceleration, acceleration + climb etc.

+1. I was flying at constant altitude (45.000 ft) and fuel flow was stuck at 139 from M0.8 up to M2.2+

Shouldn't work like this.

I also noticed when cruising at 55,000 feet ~mach 2 today that FF didn't change appreciably across the AB range from low to high. This must be a somewhat recent change as it didn't used to do that AFAIK.

Anyone tried the latest update?

I gave it a spin and the fuel flow changes with speed, but only a few Kg/m, then it's capped and no matter what speed it stays there.

E.g. 20k feet, full A/B @M1.0 ff is 270 (just an example number), at M1.15 is 274, then it's capped at 274 all the way to whatever speed you can reach.

Anyone tried the latest update?

I gave it a spin and the fuel flow changes with speed, but only a few Kg/m, then it's capped and no matter what speed it stays there.

 

E.g. 20k feet, full A/B @M1.0 ff is 270 (just an example number), at M1.15 is 274, then it's capped at 274 all the way to whatever speed you can reach.

The fuel flow is supposed to stop at some point, faster you go, more energy you need, but if you keep adding fuel you'd exceed the turbine inlet temperature. Now, I converted this number to imperial (because I'm used to imperial in this case more than metric), and 274 kg/min equals to 36,233 pounds per hour, it sounds like a reasonable number maybe? Unfortunately, I don't have any consumption chart here.

But yes, I think the question is more of a "should the FF stop here or later?" type question than "is this number correct now?", if you know what I mean.

By the way, just spoke to Mirage pilot from a french squadron, I asked him about the fuel flow at Mach 1.1 at 20k feet, he said "That matches".

Nice. :)

That's all good guys, but did you realise I specifically said in my post that I pulled that number out of my a**? It was just to explain...