Exactly, just like the picture indicates.:diablo:

right.
on to the second question:
if I give up a cambered airfoil, upper surface curved. bottom surface flat. where do you expect its zero alpha lift is? is it positive (meaning upwards) or negative (meaning downwards) or zero?

Btw, I am quite familiar with N-S equations and Bernoulli’s equation, so you can feel free to go ahead to show your amaterism:diablo:

actually no need for that deep, just basic stuff would do us fine.

Aint that quite obviously?

The combined force should go somewhat upwards and somewhat backwards.

Let me make sure that this is your answer,

so you are telling me that it is your belief that:
a body which has its lower surface curved and upper surface flat, would generate upwards lift when it’s incidents to the airstream is at 0 degrees.

is my description of your answer correct?

That’s right! The amount of body lift contribution also varies by AoA and Mach number. The F-16’s fuselage generates very little lift in level flight, but as much as 30% of total lift at alpha > 9deg and Mach 0.9 (forgot altitude). This is due to the strong vortex generated by the LERX at high alpha interacting with the blended wing-body upper surface. The F-22 and F-35 would generate even more body lift with forward fuselage shaping and integrated inlet-fuselage design.

Flanker and the T-50 would do a lot better with their flat fuselage, and it was said the engine mount + flat integrated lifting structure provides extra lift during supersonic flight due to an effect known as wave riding.

The problem with vortex lift from LERX/forward fuselage is the lift is generated ahead of the CG, hence producing significant pitch up moment at high alpha before deep stall. The pitch-up moment, if not countered, would tend to increase the AoA of the aircraft, creating a positive feedback (hence negative static longitudinal stability). Modern flight control system at this time would droop the elevator/elevon to counter the pitch-up moment.

If the pitch control device cannot produce the required pitch-down moment at high-alpha, the aircraft is simply not controllable. The F-16’s tail at AoA > 36deg cannot generate enough pitch down moment to return the aircraft to level flight. A technique known to the F-16 pilots is to keep pitching UP the aircraft post 70deg AoA, then back down and use the inertia to get the F-16 down below 36deg AoA. F-22 and T-50 pilots won’t have to do this trick since they have vector control.

The rationale behind J-20’s design was, according to early designer Song’s paper, to use the canard as a lifting device, and to dump that canard generated lift at high alpha when the elevons just simply aren’t able to generate more aft-body lift to counter the pitch-up moment. Obviously thrust-vectoring wasn’t in his mind when the paper was written..

good summay my friend, actually excellent summary, should be in some text book somewhere. 😉
the idea on generating lift on body is lways that in level flight you want to minimize the drag, but in high AOA you want your inboard and your body to do the most lifting for you. thus you see the shaping on the body trying to hit the sweep spot on drag polar when you are at cruse alphas.

Now we are done with the body lift topic, can we go back to S-duct? The J-20’s forward fuselage isn’t wide enough to cover the area of two engine faces, therefore there must be line-of-sight coming from the engine face to the intake unobstructed.

The idea is not to have a wide band in azimith where the engine fan is visible. even with a not carefully designed S-duct one can have rather bad scatter.
and also DSI and the scoop can also be designed to minimize returns.

A lifting body is an aerodynamic body where lift is provided almost exclusively by the fuselage and wing area is minimized or nonexistent. Plenty of aircraft generate “body lift” but that does not make them lifting bodies, as they still primarily generate lift via their wings. The Wikipedia article you cited could have told you this.

man,
why do you have to spoil it.

I will indulge you. since it has some technical merit.

LOOOL, SO you are trying to deny that F-22 is a lifting-body design?

I will employ socratic methods with a question and answer format, I hope you can indulge me:
first of all, the cross section you attached with your first post on this issue. please do tell us which way the lift vector goes if alpha = 0?

And I am all ears about your proper way to qualitative and quantatively describe that how F-22 is not lifting-body and whilst SU-27 is

again, I think you misunderstood the concept.
nether is a “lifting-body”,
but for both aircraft their bodies produce substantial lift increments at angle of attack.

Just show me my dare amatuerish pesudo aerodynamicist
:diablo::diablo::diablo:

don’t blame me for not giving you any warning. 😉

[QUOTE=SGW06;1689224]I cannot believe the amaterism demonstrated by some of our memebers.
[QUOTE]

it’s ok, relax, vast majority of people who come here and comment do not work in this area. hence they do not some times know the basic proper terms.

And Russia has more programs to cater to with that increased defense budget as well. It has to maintain its strategic and tactical bomber fleet, take care of having its nuclear balance with the U.S in check etc. All these don’t apply to India and I would say India has more money to spend on its Air Force than Russia.

I also think Indian labour is cheaper than Russian as well.

In industries like these labor cost is very little of over all costs.
to have a bunch of in-experienced engineers running around like chicken with their heads chopped off and delaying the program is where it is at most expensive.

on project side imho India military-industrial complex has demonstrated a consistent inability to deliver what it promises at costs it promises and (most important) the schedule it promises.

see my reply in blue.

It seems that you prefer to rather play with words instead of delievering any meaningful comeback regarding techique details.

on the contrary.
at least I informed you what you meant was technically called “pitching moment”. at least get the technical terms correct that’s a very healthy start of a technical conversation.

The link I provided basically told you that very simple concept of lifting-body or body that creates the lift (whatever words you want to play with, LOL[/B])

The link you provided me is from wikipedia. it tells me nothing new or relates to nothing to what my central message was w.r.t. “lift bodies”.

And yes, lifting-body just means a body where generates lift, don’t dodge, and yes, NASA has built many subsonic, under-atomsphere, low mach lifting-body demonstrator where the aircraft has NO WINGS and the lift is created by the lifting-body.

I did not say anything about lifting-bodies doesn’t exist. my problem has always been the undisciplined way the term has been throwing around. and my comments on that was meant to shine some insight on how fighters and transport world does things wrt lift generated from body. It does not serve your argument to keep repeating “lift bodies exist” therefore “we can approach certain technical details in an incorrect manner”.

and btw, a lifting body typically means a vehicle where its primary lift is generated by its body (oppose to a proper wing). it does not mean body that generate lift.

So don’t waste my time, your amaterism has betrayed your wanna-be-ness, so we all know you just get pwned, I have no time to waste on you on word-playing where I am sure you are quite good at.

I am not wasting your time, I may be wasting mine but defintely not yours. by converse with me at least you have been informed of the correct usage of the technical term “Pitching Moment”.

btw, did you go on fyjs.cn and pm the moderator and ask him who I am? 😉

btw, why would I be a “wanna-be” if I am already there? and do tell me your extensive resume in the industry or even academia.