The options I gave were those that the FCBA/FJCA IPT arrived at, in their order, not mine.

If we absolutely have to have a carrier, then my choices would be F/A-18, Rafale M or Typhoon (N) – probably in that order of preference.

Not necessarily.

What is the full flight envelope?

The alpha and g limits cleared by the customer’s airworthiness people (for example QinetiQ) may meet the requirement as laid down and still be below what industry have demonstrated.

Scorpion,

A VERY reliable source tells me that he’s still not allowed to fly to the limits that Keith Hartley used in 2000, and he thinks he’s below Keith’s 1998 limits, too.

That’s with the latest FCS standard, too.

I begin to wonder whether we’ll ever see a repetition of the DA1 display at Farnborough 2000.

Kovy,

Again, I’m sorry, but language differences have got in the way.

All FBW FCS systems will impose limits to prevent the pilot from over-stressing the airframe (the Russians use soft limits that can be ‘pulled through’ with extra stick pressure). That’s what carefree handling is all about.

The point that I was trying to make was that if you needed to stay below 9.3 g at a particular speed, the French might impose a 9.2 g limit, whereas the overcautious, risk averse Brits (QinetiQ) and Germans would ensure that Typhoon was limited to 8.9 g.

This is a good thing for Rafale, not a bad thing. A strength, not a weakness.

This does not reflect any low degree of confidence the customer (all four air forces, not just the RAF) has in Typhoon’s FCS, since the opposite seems to be the case. The pilots I’ve spoken to about it (from industry and the air forces) all have great confidence in the FCS, thanks to the carefree handling, and think that the limits are too cautious. It’s more about a cautious and increasingly risk averse culture, communicated via the airworthiness authorities, and that risk averse culture is evident in all programmes, not just Typhoon. Things may be worse with Typhoon, because the limit set across all four nations will usually be the lowest limit from the most conservative of the four partners, leading to a ‘dumbed down’ aeroplane with over-cautious limits.

“But why do you hide that the centre of pressure is near 25% MAC for delta wings?”

I don’t hide anything. Centre of pressure varies according to planform, section, etc.

That’s funny how you quickly translate the instability problem into an agility/manoeuverability problem.

I don’t have a clue what you’re trying to say. I don’t see instability as a ‘problem’. If you simply mean why do I mention agility, it’s because the primary reason for adopting an unstable configuration is to give the required degree of agility – smaller control surfaces, reduced drag, etc. are benefits, of course, but they are ‘by products’.

What are you afraid of? Why do you feel the need to drop the FCS into the equation?

I am afraid of nothing. If you have a highly unstable configuration, the FCS is inevitably part of the equation, as that is all that stops you losing control and breaking up.

And why do you see a design choice (whether the FCS allows something or not) more as a major limitation than a well thought tradeoff that takes into account many datas including human factors?

Again, I don’t really understand what you’re saying. Don’t get me wrong – si je pourrais communiquer dans même Français écrit un quart comme vous des types employez l’Anglais, je serais enchanté. Mais je suis désolé, je ne peux pas.

My point is that the potential degree of agility conferred by Typhoon’s instability is above and beyond what the airframe could handle. If the FCS allowed the max pitch rate, the aircraft would be over-stressed in an instant. The FCS has to intervene to limit the pitch rate and the rate of g inset to the maximum commensurate with pilot and airframe limits. Thus what the FCS allows is the limiting factor.

I don’t see this as a limitation.

Yes, I bet you’re twisting the discussion toward yet another supposed weakness of the Rafale. As usual…

I don’t see many people who would dispute that Typhoon has greater supersonic agility than Rafale – though many would dispute its significance.

Bringing up the limits imposed by an FCS is, in my view, likely to lead to a potential strength of Rafale, not a ‘supposed weakness’. I think that the two aircraft are very closely matched at lower speeds – I think that Rafale may enjoy a slight edge in high Alpha handling, while I think that Typhoon may enjoy a slight edge in carefree handling, in accurate nose pointing, and in pitch rate – before the Government test centres impose their own limitations and limits. I don’t base such opinions on mere prejudice – I simply haven’t seen Rafale match the Typhoon HAVV roll, for example. But at low speeds, I think that the aircraft are so close that service limits provide more of a differentiator than latent aircraft limits, so that Typhoon prototypes, flying to more liberal limits, out-perform production, in service aircraft by a worrying margin.

And having seen the way in which in-service Typhoons are still not cleared to the limits being flown by Keith Hartley in air show displays as long ago as 1998, it would not surprise me were I to learn that Rafale has less conservative limits, and that service Rafales may fly closer to their ‘max performance’ than service Typhoons can. This may even give them an edge in some parts of the envelope.

Certainly, I would expect French FCS limits to err more on the side of maximising performance than on the side of providing the maximum possible safety, and I’d expect Typhoon to err too far in the opposite direction. Not a good thing for a fighter.

I’d expect Dassault to have progressively increased alpha and g limits as flight testing expanded the envelope and justified the raising of limits. Only in the EF nations does the reverse happen, as over-cautious and risk averse folk at QinetiQ and elsewhere enforce tighter limits.

Like the Tranche 2 production contract, the T3 contract will be signed at the last minute (or after it!) and only after intense negotiation. Before Paris, EF GmbH were talking about the need to start talking about it ‘soon’, if we are to avoid a production gap, but I don’t think anybody expects it this year…..

Scorpion.

You need to understand that the figures of 35% (not a figure I have used, or recognise) and 45.61% refer ONLY to the centre of gravity position in relation to the mean aerodynamic chord.

All it tells you is where the C of G is, in relation to the average chord line.

It does not tell you where the centre of pressure/centre of lift are, and so tells you nothing about the resulting pitching moment. If the Centre of Gravity is behind the centre of lift the aircraft will tend to pitch nose up – the distance will exacerbate that pitching moment.

Nor does it take account of canard or tailplane position, size and moment arm.

By themselves, the figures are almost irrelevant.

To compare levels of instability, you really need to know the time to double amplitude. To then translate this measurement of raw instability (what would happen without the FCS holding everything together) into agility, you then need to know what maximum pitch rates and g onset rates are ‘allowed’ by the FCS.

If you have half of the pieces of a two piece Jigsaw, you have only half the picture.