The F-22 has a higher fuel fraction over the F-15, and we don’t even know what the j-20’s sfc and fuel fraction are.

Really?

The “empty” fraction for the F-22 is 0.29, whereas for the F-15 it is 0.32.

At MTOW that changes to 0.22 and 0.20 respectively.

For comparison, at MTOW, the MiG-31 has a fuel fraction of ~0.33.

If you don’t mind I would like to address an earlier point about the j-20 and body generated lift. I do not know if it is significant but the j-20 does have some body curvature. I noticed it in one of emile’s pictures.

It does, it has a little around the cockpit sides and drops down toward the wing trailing edge. However compare the upper surface camber to that on the T-50 and F-22.

One will operate very well at low angles of attack, the other two will perform significantly better at larger angles of attack…

I don’t think J-20 is any kind of pure interceptor, due to the volume of interceptors, those were always larger than contemporary fighter, he expressed interceptor heavy class, I saw what did he mean.

The fuel fraction of the J-20, coupled with its large finesse ratio, means it is a design built for speed over maneuverability.

That does not mean it cannot maneuvre, but it does mean some sacrifices have been made to what the maneuverability could have been to benefit speed and range.

Hence why I see it as an interceptor/interdictor more than an aircraft bred for dogfighting.

Erm…

A fundamental aim of combustor design is not to increase pressure within the combustor, but instead increase kinetic energy by allowing the flow to accelerate as it expands due to temperature increases.

Within a reciprocating engine, there is the pressure build up, this then leads to moving the cylinder and a resulting expansion of the gas.

As a turbine operates on the Brayton cycle, increasing pressure prior to combustion increases efficiency. Subsequent increases in pressure are both detrimental to this goal of increased pressure prior to combustion and to extracting energy via the turbine.

If J-20 was a striker we wouldn’t be seeing J-20’s configuration as it is now — i.e: no canards, and likely no all moving tails either.

Why not?

I want a rational argument, not a reference to some press release 8 years ago by some PLAAF general who consistently publicises the truth, the whole truth and nothing but the truth.

Rant/post over. Hopefully I’ve convinced anyone who still thinks this aircraft is a dedicated striker or interceptor otherwise 🙂

If your going to convince someone like myself, your going to have to come up with a lot more than that.

I dunno. Why would the third largest country in the world by landmass want a long ranged interceptor… its just beyond me. :rolleyes:

but to me the top lip of the Nacelle seems to be above the wing leading edge

That in itself doesn’t necessarily matter.

meaning point 2/3 are significantly compromised

No – meaning point 2/3 may be significantly compromised if appropriate steps are not taken to handle the potential problem.

Also as the cord line of the engine gets closer to the wing cord achiving zeroshock-induced BL separation becomes somewhere between very difficult and impossible.

Sorry – but what?

I assume you are talking about the reduced pylon length between wing and nacelle?

‘Back in the day’ it was assumed that the gap would have to be of the order of 1 nacelle diameter. That quickly reduced to 0.5 diameters.

Recent times, its under 0.1 without any significant problems. NASA have previously done work on much closer integration (late 90s if memory serves – check the ntrs). You need to consider lateral curvature of the pylon to control this, but its well understood and not a big deal for Airbus/Boeing.

A supercritical aerofoil pressure surface may, indeed usually will, have a weak shock on its lower surface, but this is usually 3/4 or later chord length. Due to the weak nature of this shockwave, there is no BL separation on the pressure surface of any well designed (i.e. any Boeing/Airbus) wing.

The nacelle bypass shroud has long since terminated by that point, and your into the flow downstream of the nozzle, which is underexpanded anyway with a very complex shock structure. But this is normally separate from the small transonic pocket on the wing pressure surface.

Just 18 months ago Boeing were talking about the 737 being at the end of it possible development due to problems around the integration of a larger fan engine.

It is the same PR bullsh!tters that tried to disparage the NEO now trying to maximise everything to do with the 737 re-engine. They are best treated without outright contempt, or, at least completely ignored.

I’m fairly certain the engineers would have completely backed a re-engine. They know fine well propfans are absolutely key to the next generation single aisle, and that any new frame built before that is on a hiding to nothing. But that doesn’t stop bullsh!tters like Albaugh coming out with complete p!sh – he’s a project manager – never designed a f**king aircraft part or system in his life.

With regard to the aerodynamic comments, does it seem realistic to be making assessments based upon artist renderings? Shouldn’t one wait until they see something a little more definitive?

True. I just quickly want to quash the absurd notion that Boeing would actually design an aircraft where 10% of the wing is not working!

I looked at the Boeing website and did not see any cockpit renderings. I’m hoping that Boeing ditches the 1968 overhead panel that Southwest mandated for the NG, and also installs a modern EICAS/ECAM type system.

I think they are strongly insisting on keeping the cockpit common to eradicate any (or vastly reduce) retraining of glorified button pushers/pilots.

Boeing is a company that hires people to build airplanes, Airbus is a political consortium that builds airplanes so they can hire people.

Now, now, behave.

I guess Hawker-Siddeley, English Electric, Vickers-Armstrong, Bristol, De Havilland, Sud Aviation, Aerospatiale and Breguet (to name a few) had no history of building aeroplanes prior to their combining? :confused:

Using the same yardstick; would that mean that the combination of Lockheed, General Dynamics and Martin into Lockheed-Martin mean they are a political consortium that builds aeroplanes so they can hire people?

Or Northrop and Grumman?

Or McAir and Boeing?

Due to the smaller size of each European country relative to the US, the consolidation process of indigenous companies started much earlier – which maybe is what makes it harder for… ‘an outsider’ (for lack of a better term) to see the lineage. The combining of the respective companies into Airbus was largely driven by the private companies need to lump together to survive, not by the politicians.

[Oh, and for the avoidance of doubt – while I know there are some incredibly smart people at Airbus – I also know there are a large number of inept bstards there too – particularly within their procurement branch. There is a culture of ‘zero responsibility’ within the company as well as a culture of ‘managers’ and procurement zombies leading chief engineers, which may or may not be different at Boeing.]

1. If your close enough to get a fix on the F-22 by it’s radar signals, then why don’t you have a AIM-120 inbound already?

Perhaps because your still outside the engagement envelope.

I keep saying it, you keep ignoring it. You folks are placing far too much faith in “L”PI.