I hope you are not following the lead of an earlier poster on this forum who claimed that the only way to validate missile performance was to conduct warheadless friendly-on-friendly missile firings.

The way you prove missile performance is to set up a trial against a target near the limits of the missile’s capabilities, use the range instrumentation to check that the target presentation and launch conditions are exactly what are desired, fire the missile, observe the results, then compare those results with the missile trajectory and behaviour predicted by pre-trial modelling. If the two do not match, something is wrong.

I am still comfortable with my assertion that the only way to accurate gauge missile effectiveness is indeed trails on “live” aircraft.

Of course, the risk of actual skin-skin impact could be eradicated by a pre-programmed manoeuvre out of the flight path of the target object when a second or so away from possible impact.

Putting together a canned fire test is a good way to validate models of both control and aerodynamics. But as you well know, models don’t always… in fact, rarely, work accurately when asked to predict with too many variables.

I find it amazing that no airforce has arrived at the conclusion they are betting billions of dollars (in the case of the bigger ones) on items they have never taken the time and money to actually prove the effectiveness of. Why is there not training rounds that have the aim of getting to within 1-2 seconds of the target, then aborting the intercept, deploying a chute and being recovered for reuse?

If I was Phillip Hammond, I’d be saying put up or shut up to the RAF, the RN and MBDA/Thales etc. The MoD happily burned billions on Nimrod, a fraction of that spend could turn out to be priceless for the effectiveness of the RAF/RN.

I’ll have a great day thanks. I know what I’m talking about unlike some people.

I don’t see flight mechanics there anywhere. Which is undoubtedly the root source of this problem (and the Breguet range equation issue in the Eurofighter thread).

A mechanical engineering degree with a few aero modules tacked on is good – but don’t assume it makes you infallible on all matters aeronautical. Assuming you did graduate 14 years ago, then you really should be wise enough to know that by now.

Unfortunately, I’m too busy at work to settle this once and for all (by building a workbook to demonstrate it all) – if I get time over the next few days, I’ll see if I can throw something together.

Yes and which aircraft will be affected more by added weight? The heavier aircraft with the higher TWR or the lighter aircraft with the lower TWR?

Depends what each aircraft need to perform the role.

Mission capability is not defined solely by the weight of loadout.

Yeah….. the problem is that I’m talking to people who don’t understand maths or physics.

Dead on kid. Stick around and you may learn something.

Why has he used the Mirage climb rate for axial velocity?

Ask him. I’d hazard a guess its because he has good data for it and can have some confidence in producing correlations, which can to an extent be verified from within the data.

What the hell is he doing with those percentages?

Approximating. Rafale has 1.59x the thrust of the M2k, 1.11x the wing area and 1.14 I don’t see an origin for.

The differences are applied incorrectly as you point out though.

How does he even get the answers he gets with the calculations he’s posted?

You point it out yourself below so are well aware of how it arrives.

Wrong numbers, wrong method, wrong execution.

Correct, with the thrust and drag being addition/subtraction, a simple ratio cannot be applied.

Given that it is (T-D)/W, then ratios could be taken to make the difference, (T/W)m2k and (T/W)rafale along with a rough Cd* calc for both wing areas assuming constant aerofoil. Dirty and not particularly accurate, but better than the usual pissing contests in here.

*assuming he has enough data to estimate this

If you think that’s what happened, please surgically remove your brain and flush it down the toilet where it belongs.

I don’t think thats what happened at all.

I think you again tried to be a smart-**** and failed miserably.

Well sadly it’s impossible. Everything from the thrust-to-weight difference to the selection of a lower drag fore-plane arrangement makes it impossible. Then you have the ramped intakes playing to your advantage in a supersonic climb too. No way, no how.

It could depend on what the scenario was.

As it turns out, empty and unloaded aircraft aren’t terribly useful when it comes to performing tasks the military may actually be interested in.

simplifies to:

(T-D)*V = W*V

Which is remarkably similar to…

Force = Thrust-Drag

&

Energy gain rate with respect to time = dE/dt = Force * Distance/dt

You’ve basically corrected him for simplification of the equation, then come full circle and agreed with the simplified statement.

Still, I’d expect Wichita Spirit plant can soon produce replacements, so it’s not a huge issue, but I’d suspect it might cause some jiggling of production at Spirit and Boeing.

Actually, I’d think it quite an issue to conjure up 3 fuselages [without having a cascading effect on subsequent production]. The supply chain is just not rigged to yo-yo rates quickly.

I would think Boeing will just have to rejig the delivery slots and that’ll be it, they’ll probably catch back up the fuse shipsets vs. wings in a few months.

What is negative stability

If the aircraft experiences a nose up or down disturbance, the aircraft will continue to pitch in that direction without correction from the pilot/flight control system.

In a stable aircraft, the natural balance of forces from wing and tailplane will correct the disturbance and restore a steady level flight condition.

[just using pitch as an example]

I note you didn’t address the point about 3,000kg being a low fuel density for two x 2,000L anyway.

Don’t care about it.

No it bloody can’t be ballpark. You can’t just guess values of k and Cd0 and make up TSFC figures. 21g/kNs = 2.1E-5 kg/Ns. 0.685kg/kgfhr = 1.94E-5 kg/Ns

So, I used 2.22E-5 and 1.86E-5 (from the same book), you go nuts and quote numbers of 2.1 and 1.94 from disparate sources (albeit quite good ones).

Now. Thing is, at cruise, both of those TSFC values will jump by a factor of ~1.5 for installation losses.

a Su-27, which has a stated range of 3,530km:

OK, using your TSFC (x1.5), and the premise that the range is from OEW+max fuel, then that gives an L/D of ~9. [which would be somewhere in the right area – using F-15 k and Cdo values, I got L/D=9 for EF and 9.6 for Su-27]

Now, I’m going to use that L/D=9 and apply it to both Su-27 Eurofighter. Before you go biccies about not being able to do that, be aware it is almost certainly a favourable assumption for Eurofighter by dint of its significantly lower wing aspect ratio*.

It spits out a EF internal fuel only range of 2860 km. [Not too far away from the stated 2900km.]

*If you worked out the L/D factor using K and Cd0 (based on F-15=Su-27 for both a EF and Su-27 @ OEW+Fuel, then the EF would need a >7% improvement in both Cd0 and K to match the Flanker. I must emphasis that 7% is a vast chasm! To highlight that difference, even the F-5 has an L/D of approx 9 at CL=0.225 at Mach0.9

So, once again scooting through the numbers, the Flanker can match Eurofighter’s range from OEW with a fuel load of ~67%. Running from MTOW, the Su=27 fuel load can drop to 59% total possible! [with range for both dropping to ~1800 km]

and the Su-35 has TVC, which improves range.

Your going to have to explain that to me. A relaxed static stability aircraft flying subsonically will see nothing but extra weight (and possible nozzle efficiency compromises) in cruise.

Now using simple fuel amounts.

It is not a direct ratio problem. Please stop treating it as such.

Furthermore, you are grabbing numbers from all over the place without any verification of consistency.

The Typhoon’s range on internal fuel cannot be less than the ferry range divided by internal fuel+external fuel multiplied by the internal fuel. That’s the most mathematically senseless crap that anyone could possibly come up with. Breguet is clearly on drugs.

OK, so. Eurofighter can carry 2x2000L + 1x1000L tanks. At density .876 kg/l that is 4380 kg extra fuel. A rough rule of thumb for EFT is that half the extra fuel is burned compensating for the tank drag.

Thus, I’ve increased the Eurofighter fuel capacity to 5000+[4380/2]. Putting it through the same range equation with same parameters as used above gives an answer of….

3840 km.

Which is not a kick in the teeth away from “> 3,800 km”.

For the Flanker, 2x2000L = 3500 kg @ 0.876 kg/l, again, rule of thumb, effective increase is 1750 kg; resulting in a ferry range of ~4500 km.