Amiga500instead of asking why the EADS offering is so low, maybe we should be asking why the Boeing offering is so high
seriously, if they’re offering a smaller plane and have a significant fuel-burn advantage, why the heck do they cost so much more?
Easy – the A330 MRTT is already flying.
The Boeing contract has to fund the entire development of what is basically a new aircraft.
The B767 Frankentanker is a far bigger undertaking than the A320 NEO… Airbus estimate that it will cost between $1.3-2 billion for the NEO program…
Amiga500very easily actually.
I suggest you go look at the area centroid of the wing/canard with respect to the c.g and the aero centre positions before thinking they won’t recover from such stalls. π
(That is after all… how the Flanker was first able to do the Cobra)
Amiga500This is why the gripen has had problems with “deep stalls” whereas the eurofighter and rafale has not.
WHAT?!? :confused:
Do you know what a deep stall actually is?
I look forward to you explaining how a canard configuration can experience unrecoverable deep stall.
Amiga500So when will the England rugger team get their personal airliner and what is it likely to be….??:)
A rickety old chariot that’ll swing low.
Hope the Welsh stuff them tonight.
Γirinn go BrΓ‘ch!!! π
Amiga500The trade off with the Leap-X for the 737 is that it will spin faster. So more noise!
I’d be fairly sure that’ll also come with an associated increase in fuel consumption… (unless they are going to design a turbine especially for the 737)
Amiga500CFM has said a Leap-X for the 737 would only be marginally larger in diameter and fit under the wing with the current gear.
You sure?
Is it not a case of; they can get away with just a nose landing gear mod for Leap-X?
(While GTF requires the whole shebang)
I also wonder what compromises they would need to make to wing-pylon design to fit the engine underneath, I’m sure it would be compromised more than the aero-heads in Seattle would like.
New blade technology would allow the 737 version of the Leap-X to have fewer blades up front, but the same BPR as the A320NEO.
I think the way the ducks are lining up, the GTF is a sizable step ahead of Leap-X. I cannot back that up with any weblinks, but rumour and gossip would (quite strongly I would add) suggest that is the case.
But yeah, to summarise your (valid) point; Boeing have a single escape route of sorts. Not ideal by any means, but it would avoid a complete surrender of the market to the NEO.
Amiga500IMHO part of the problem in this case is that the 737 platform is by now well and truly hitting its limits.
Absolutely.
The 737 cannot fit a larger diameter fan under the wing. Unless Boeing are prepared to lengthen the landing gear, and that comes with a host of associated problems.
Unfortunately, a clean slate design for 2020 from Boeing would be a disastrous move. They would miss out on a number of fundamental step changes in technology that would doom their design to ultimate failure once the Airbus next-gen single aisle arrives.
It would be a complete role reversal of the original position the A320 found itself in on introduction, expected to be decimated by the 7J7 and MD-94X.
Amiga500Whats the specs on it (relative to the competition)?
Amiga500As far as I know, Key Publishing’s magazine is Airforces Monthly, not Politics Monthly…
Carry on discussing… airplanes.
Now now. π
“War is nothing more than the continuation of politics by other means”
– Karl von Clausewitz
But yes, point taken – different political systems are rather irrelevant to the PAK-FAs performance.
Different needs derived from the different foreign policy attitudes of different nations however, is not irrelevant.
Amiga500So let me make suepre I am getting this right, you have attended aerodynamics lectures where area rule was discussed, but somehow you missed out on learning that high subsonic speed aircraft, such as the 747 experience some transonic airflows over their fuselages?
Okay…
I take it you’ve never actually been involved in the design of one of these things?
Aside from the obvious minimising of adverse pressure gradients (through nose length/diameter ratios etc), one thing dictate the shape:
How many passengers you want in? (All variants.) You then compromise wetted area against tail lever arm (tail volume ratio) against structural weight and a few other bits and pieces to give your optimum for the different variants – then compromise those to give your final fuse diameter. Everything is then driven by that.
Slenderness ratio doesn’t really drive anything for LCA (fuse) design.
The desire for a constant fuselage diameter for the passenger-compartment over-rules us aeroheads.
The wing fairing on the fuselage will have some work with the ruling. The wing, nacelles and pylons will have extensive work done based on the ruling – but not the fuselage, its mostly other factors that define it.
I believe (in your defence) the 747 upper deck was modified to reduce the strength of the sonic bubble above it, and any resulting shock induced BL separation. But the upper deck was there as a result of the 747’s origins as a cargo carrier.
Amiga500Does that not suggest something about the aerodynamics of the airframe?
The low top speed also suggests something about the airframe.
Amiga500Of course commercial airliners and bizjets have to keep transonic Mach effects in mind. But it’s mostly about avoiding draggy local shocks that also create vibrations and if in the wrong spot will seriously hurt controlability.. Look at high-numbered Gulfstreams, the Citation X, or a Convair 990 (that one flew really deep into transonic territory). And a delta like the Concord is by definition very area ruled and perfect for low supersonic drag.
The F-35 is actually a very fine example of area ruling. Look at how the belly shape tries to compensate for intakes, wings, tail surfaces. Quite impressive. Still has a huge cross-section and isn’t sleek, but Lockheed tries its best to make it work.
BTW – why would a 747 fuselage seek to conform to the Mach area rule?
Fuselage buddy, fuselage.
I’ll freely admit, there are many more tricks that can be played to keep the wings right.
The belly shape of F-35 has been designed for what it has to carry (the damn lift fan). The aerodynamicists have played second fiddle to that. You can only polish a turd so much. π
Amiga500And if we were in 1950 I’d agree with you. But we’re not. F-35 doesn’t conform to the “traditional” area rule, but then neither does the F-22 nor the B-747.
Aero-dynamicists have found may ways of implementing the area rule and the traditional “cigar shape” is not the only way to do so.
They have?
I must have skipped all those aerodynamics lectures that covered that then. :rolleyes:
BTW – why would a 747 fuselage seek to conform to the Mach area rule? No LCA has ever done so, apart from *maybe* the Concorde… even then, I’m not sure it did.
The F-35 tries to conform to Mach-Area rule by swapping lateral expansion for vertical contraction. You’d need a windtunnel to know if that works or not, but the relatively poor top speeds would suggest not (or they’ve severely compromised their engine/engine intake for subsonic thrust).
Amiga500You’re putting words into my mouth, or rather my post. Never once did I suggest that drag lowers, the faster you go.
What I stated was that the airflow ‘smooths’ out when out when you are truly supersonic with the airflows in the transonic regime being more turbulent.
You are making a big deal of it all right.
So what if it smooths out. If it is less turbulent but the drag is higher… who cares as long as you don’t experience control reversal or Mach tuck or similar.
I would suggest that this explains why so many aircraft are able to pass through the transonic flight regime and fly supersonically using reheat but are then able to ‘throttle back’ and remain supersonic on dry thrust only.
I would suggest it has much more to do with the relationship of total to static pressure to Mach number… i.e. it is a square relationship.
The higher your Mach number, the higher your additional inlet compression for your engine. That means you can dump more fuel into the combustor and keep the same fuel:air mix and get more thrust out without having to use burners.
Example: Concorde. The Olympus engine had an OPR of about 15. But, couple that with the intake compression at Mach 2 and the effective pressure ratio increased to about 80.
I wonder if this can truly be considered “supercruising” though because as I understand such things the apparent main benefit is the decreased fuel burn when using dry thrust only compared to reheat, but if you HAVE to use reheat to GET supersonic in the first place (even if you can remain there on dry thrust only) then I’d suggest many of the benefits would be eaten up through the use of that reheat.
I would strongly suggest not.
An engine on afterburner will use around 3-3.5x the fuel of the same engine at full military (based on typical R-25 and J79 figures).
Acceleration through to “supercruise” will take (unless you are in a superhornet) around 1.5 mins at most. So you are burning an additional 5 or 6 mins of equivalent military power operation in worst case scenario.
It is also not such an amazing or noteworthy capability as many aircraft have proven capable of ‘supercruising’ this way.
Indeed. Which shows how stupid it is to be arguing about it, and how stupid it is for Lockheed to be blowing out their ar$e$ so much about it.
By their (LMs) definition, the F-22 is better at supersonic cruising than the MiG-31. Unfortunately the F-22 can only do Mach 1.8 for 400-500nm. The MiG-31 can do Mach 2.3 for over 600nm… whoops.
I then wonder when I’ve never seen SAAB claim to have passed entirely through the transonic ‘regime’ on dry thrust alone and why they wouldn’t make that claim IF their aircraft can do so?
Because no one (outside fanbois on message boads) really cares?
PS, Amiga500, did you note what your own link to that Code One article stated? The bit about later model F-16’s supercruising on dry thrust…
What link? I’ve linked nothing here bar a graph… and that definitely was not from LM.
Strange that L-M doesn’t trumpet that capability to the world. They also are not backwards when it comes to promoting their products…
Or could it be that the capability is actually of such little tactical benefit in the case of an aircraft LIKE an F-16, it’s not worth trumpeting?
What was the loadout when doing it?
Amiga500What you guys really need to understand is the dynamic performance of the engines and the intake systems. As madrat was saying unless you know this evaluating drag at supersonic speeds using static/sea level thrust is absolutely pointless. There are big design variations in inlet pressure for similar performing engines due to decisions made my the engineers. That however doesn’t translate into being able to calculate the relative drags of the two airframes and therefore there respective accelerations etc. You would need a scaling algorithm. After my design project last year with airbus and rolls royce on relatively simple inlet designs for 30000~50000 lbf engines and seeing the actual data – you would realise you can’t compare things the way you are doing.
Its not even dynamic intake performance, its steady state. Dynamic intake performance would be under large changes of (intake) angle of incidence to freestream.
I have an idea of how much it can change, I did post about the effects of the inlet here. π
You also need to understand, that as the engine OPR increases, that means they can (and usually will) dump more fuel into the combustor to achieve the stoichiometric ratio…
Yes, it is far more efficient to get the extra thrust from additional inlet compression rather than dump fuel into the nozzle for reheat/afterburn. But it does not come with zero fuel consumption penalty. Hence why I am dubious about the TSFC dropping from Sign’s aircraft (2) to aircraft (1), despite it having a (potentially) 43% higher inlet compression ratio (assuming both inlets are operating pretty well at Mach 0.9 – which should be a reasonable assumption, Ξ· should be about 0.95 for both).
Oh, and you also shouldn’t be applying the logic of civilian HBPR nacelle inlet design to supersonic fighters. For a start, fighter designers do not use the spillage around the nacelle leading edge to generate additional thrust, nor are fighter inlets (usually) fixed. π
Also its good to see that you realise drag still increases after the transonic cd rise – because of the velocity squared parameter being a non linear increase in drag.
I’m not sure everyone does.
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