How much trim control do LEVCONs provide?

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vilters

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Unread post17 Aug 2018, 16:10

Well, I fear you just changed all laws of aerodynamics for delta's.

On a delta wing, => Trailing edge surfaces down means ; => Hello ground, here I come, and the next thing you hear is the impact.

Remember the horizontal "S" curve.
Take a Mirage 2000 series. => At LOW speed the LEF goes DOWN and trailing edge goes UP, right up to the stall where LEF are MAX DOWN and the TEF are MAX UP. => The maximum "S" curve.

AGAIN, and so sorry but for the last time; A Pure delta HAS no conventional flaps.


ON A PURE DELTA; The trailing edges serve as elevator and aileron, but NEVER, and I repeat NEVER as flaps.

ONLY on canard airframes, like Viggen, Rafale, Tiffy, can a combination of the canard and LEF and TEF get the TEF to act as Flaps, and even on those airframes, the FLAP function is Minimal to NON-Existent.

Allow me to suggest to buy a good book about aerodynamix.
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vilters

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Unread post17 Aug 2018, 16:33

[img][http://airheadsfly.com/2015/02/12/deal-egypt-buys-two-dozen-rafales//img]

http://airheadsfly.com/2015/02/12/deal- ... n-rafales/

Look at this Rafale Landing.
Canard = UP
LEF are DOWN
TEF are UP

This is the max lift situation.
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vilters

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Unread post17 Aug 2018, 16:38

But? LOL, I am open minded.

PS1 : A B-2 is NOT a pure Delta.
PS2 : An arrow wing, is NOT a pure delta. => Center of gravity and center of lift relationship is mostly conventional.

Just show us a PURE delta that uses its trailing edge surfaces as flaps.
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vilters

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Unread post18 Aug 2018, 00:16

What you don't seem to understand is that the slower a delta flies, the more the trailing edges move UP.

And on a delta with LEF, the LEF move down while the TEF move UP when speed decreases and AOA goes up.
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element1loop

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Unread post18 Aug 2018, 04:18

vilters wrote:ONLY on canard airframes, like Viggen, Rafale, Tiffy, can a combination of the canard and LEF and TEF get the TEF to act as Flaps, and even on those airframes, the FLAP function is Minimal to NON-Existent. Allow me to suggest to buy a good book about aerodynamix.


Allow me to suggest you quit being a smart-arse and attempt to address the thread's question on-topic even once, instead of time-wasting with more irrelevant nonsense.

I see in the above quote you've finally admitted that delta wing jets do in fact have flap implementations, especially as flaperons. And no, trailing-edge FLAP SURFACES DO NOT DEPLOY UPWARD. :roll:

Good grief.

And I see you're beginnng to construct your next time-wasting strawman within your final blurb about AOA, but no this is not about LEVCON functioning while 'pulling a cobra' or such, this is about trimming with LEVCONs during a stabilized naval approach AOA. So give that one up before you get started, thanks.

Here's the re-stated question, yet again, just so there's no doubt that you're totally ignoring it. It was re-stated after you'd ignored the original question and derailed it, and which you've kept doing, again and again since ... hmm.

collimatrix wrote:All of this is interesting and none of it answers my question; can LEVCONs provide independent trim control and trim out the pitch change from the use of flaps the same way canards or conventional horizontal stabs can?


You seem allergic to the question. You keep avoiding and failing to addess any part of it. So allow me to blow your irrelevant bullcrap out of the water:

Image of LCA TEJAS -- with DELTA WING, LEVCONs, drooping LEX, and a very obvious FLAP control surface deployment, with significant downward deployed flap deflection angle, plus the AILERONS have converted to FLAPERONS, with a matching large downward deployed angle of deflection:

https://i.imgur.com/8e2pL3P.jpg :doh:

Clearly the "FLAP Function", is not "Minimal to NON-existent", now is it? That's reality "vilters". It's quite a bit different to what you've adamantly asserted above. Note what's written on the tail, i.e. "NAVY". All of the 'liquorice-allsorts' of waffle that you've trotted-out here is simply irrelevant rubbish, from beginning to end. And this article quoted below from April 2017, also makes clear that the Tejas delta-wing has integrated "TEX flaps".

So maybe they should, "buy a good book about aerodynamix." Perhaps you could lend them yours?

Air Vehicle Configuration of LCA (Navy) Mk2 is a critical activity during the concept design phase. The major activities carried out are:

Numerical Master Geometry (NMG) V0.6L has been base lined for detail design

Improving performance in terms of low supersonic wave drag, acceptable cg limits for stability and control criteria for zero ballast design.

Optimized LEVCON & Shelf Flaps to achieve approach speed reduction for carrier landing. ..."

" ... ​Flight Control System and Control Law

Preliminary Design Document for IFCS including IFCS Architecture released. Study of alternate configurations for Active LEVCON including Single / Multiple Linear Actuators was carried out. TEX flap introduced for reducing approach speed which would provide ~5 knots speed reduction.


http://fullafterburner.weebly.com/next- ... ile-part-1

TEX flap = Trailing Edge Extension flap

So it looks like Collimatrix suspicion was probably correct, the LEVCONS may be acting as an active auto-trim, to trim out the "TEX flap" deployment, on the navalised delta-wing TEJAS.

On top of that:

Does the 'Su57' have a delta wing? No.

Does the 'Su57' have LEVCONS? Yes.

Does the 'Su57' have flaps? Yes.


What the hell are you going on about "vilters"? So much for your time-wasting strawmen, and persistent ignoring and derailing of the question.
Accel + Alt + VLO + DAS + MDF + Radial Distance = LIFE . . . Always choose Stealth
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vilters

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Unread post18 Aug 2018, 22:12

You are so bolted into your own idea that a proper discussion has become impossible.

On a side line; The last time I believed a company brochure was some 30 years ago.
LOL, Trejas brochure is as valid as the Griphens. LOL. Erase all words and what is left is true. LOL.

But, yeah, LEVCONS can trim, and do a better job as trailing surfaces trims.
LEVCON trim ADDS lift while trailing surfaces trim removes lift.

FYI : the PAK-Fa is no delta and follows conventional rules.
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Unread post18 Aug 2018, 22:45

Gripen uses a wing far enough forward it largely acts as a conventional wingform. The Gripen uses forward mounted horizontal stabilizers, but that doesn't mean flaps down makes the wing decrease lift.
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element1loop

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Unread post19 Aug 2018, 03:59

vilters wrote:You are so bolted into your own idea that a proper discussion has become impossible.


No, you are unable to address the question, at all, and totally failed to do so.

vilters wrote:On a side line; The last time I believed a company brochure was some 30 years ago.


What has that got to do with any part of this discussion? I'm beginning to see what your problem is.

vilters wrote:LOL, Trejas brochure is as valid as the Griphens. LOL. Erase all words and what is left is true. LOL.


blah-blah-blah ... useless.

This is what is true--deal with it.

https://i.imgur.com/8e2pL3P.jpg

vilters wrote:
Well, I fear you just changed all laws of aerodynamics for delta's.

AGAIN, and so sorry but for the last time; A Pure delta HAS no conventional flaps.

ON A PURE DELTA; The trailing edges serve as elevator and aileron, but NEVER, and I repeat NEVER as flaps!

Just show us a PURE delta that uses its trailing edge surfaces as flaps.

What you don't seem to understand is that the slower a delta flies, the more the trailing edges move UP.


BZZT! .... unbelievable. :doh:

vilters wrote:But, yeah, LEVCONS can trim, and do a better job as trailing surfaces trims.


You seem to imagine that trailing-edge flaps are pitch trims--NO THEY ARE NOT.

A 'trim-tab' can be integrated into an aileron, and the aileron can be designed to also act as a flaperon, while still able to use the integrated trim-tab. But flaps themselves do not trim aircraft, they induce the very opposite, an out of trim air deflection.

The question here is, can LEVCONs counter-deflect ENOUGH air flow at low air speeds, to sufficiently cancel out the flap deployment inputs to AOA change?

What is being 'trimmed' (stabilised) is the AOA between wing and the airflow, in order to maintain a pilot's desired altitude, or else to alter altitude in a desired way. Or to maintain an air speed, or else alter an air speed in a desired way.

That's it.

It is only a tool for a pilot, especially in level nav flight, to modify attitude, thus wing AOA, thus a modifier of both speed and altitude, simultaneously. You adjust pitch trim to aim for either a speed, or an altitude.

Pitch-trimmng does ZERO ELSE. This is why pitch trim surfaces exist. It is a desired performance control, nothing else.

For example: In a finals approach, you set final landing-config, set finals engine throttle, trim to aim for a landing-config speed, which results in a characteristic stable landing AOA for that airframe, and thus sacrifice altitude to get that trimmed stable speed, thus you sink, and use throttle to adjust rate of sink or climb to match glide slope.

i.e. throttle and pitch trim are both precision desired performance controls for altitude and speed stability.

With a constant throttle, you can trim to set a speed, with a resultant AOA and equivalent altitude. Else you can use the trim to set an altitude with a resultant AOA and equivalent speed. The only way to get both a stable target speed and a stable target altitude, is to alter both the throttle and pitch trim.

That is all a pitch trim does.

vilters wrote:LEVCON trim ADDS lift while trailing surfaces trim removes lift.


This is completely incorrect--absolute rubbish in fact.

Pitch trims ONLY counter-deflect airflow, up or down, as desireded by the pilot.

Pitch trims do NOT produce LIFT, they only modify the Angle of Attack of the wing, so that the wing can change lift, but only at the expense of higher drag and falling speed. Without more throttle the aircraft may slow so much that it begins to sink. And that is not adding lift. To get actual added lift you need both more AOA, and more throttle.

Pitch trims only counter-deflect air to balance the net air deflections of the whole airframe configuration, to maintain a pilot's desired speed or altitude performance and resultant AOA.

Anything else being claimed about pitch trims is bullshit.

Whether a counter-deflection to balance net airflow angle is done by a LEVCON that's forward of wing, or an elevator rear of the wing, IS UTTERLY IRRELEVANT TO NET LIFT.

Duh, right?

What "vilters" is claiming here, is that "LEVCON trim ADDS NET LIFT, while trailing elevator trim-tab surfaces NET REMOVES LIFT, which is absolute rubbish.

Trims do not generate lift! Wing and lifting-body AOA does!

All that ANY pitch trim does is modify that AOA!

So whether a LEVCON alters the airframe AOA, or an elevator trim-tab alters the airframe AOA, it is impossible for a trim mechanism itself to add any net lift!

The AOA alone modulates net lift, and ALL pitch trims alter the AOA! So LEVCONs can not generate net lift that way.

Sooo ... not only has "vilters" been consistently wrong, or irrelevant, now he's trying to create a MYTH, namely, that while operating as regular wings-level and stable in cruise that LEVCONs will ADD NET LIFT to the wings! While elevator pitch trim (he asserts) will remove net lift.

This is pure garbage.

He's apparently equated the high-AOA ( very high-drag) vortices generation (to engender air flow remaining attached to the wing longer, over more of its area, retaining partial lift) as being equivalent to "adding lift", then apparently extrapolated this to mean that LEVCONs will also magically generate NET LIFT INCREASE, while operating as a low AOA flight pitch-trim!

bwaahahahaha......... no "vilters".

It doesn't work like that, induced vortices at low AOA, over a wing skin, would create parasitic drag, which works against thrust.

And it is thrust plus wing AOA which creates net lift. It is not a f***ing trim mechanism which adds lift. :roll:

In fact an elevator trim tab would not create down stream skin drag, so is likely to be even more efficient as a location for a pitch trim (less drag). But all pitch trims mechanisms do exactly the same thing, and NONE are capable of creating net lift.

And I'm damned sure the Indians are not going to be interested in creating macro turbulance over the inner wing skin during a stabilized approach or takeoff. If they Indians wanted vertices over the wing on approach, to add lift, they would be after micro vortices generation to rough the boundry air, via using a vortex generator saw-tooth on the rear upper side of the drooping LEX surface--not ftom a freakin LEVCON!

So no, the LEVCONs will not be doing that either to extend stall envelope while functioning as approach flap-deploy pitch-trims.

Quit your ignorant nonsense "vilters", you cleatly have no clue about this and is why you didn't answer the question, and are now just creating TIME-WASTING nonsense myths about LEVCONs, that then have to be debunked.

It is a theory that LEVCONs act as pitch-trims. It may be true.

It is NOT a theory that LEVCONs acting as pitch trims, create LIFT, it is however COMPLETE AND UTTER BULLSHIT "vilters".

Knockoff your rubbish-pedalling.

vilters wrote:FYI : the PAK-Fa is no delta and follows conventional rules.


Hence you should have been reading the question and listenng, rather than asserting nonsense about the "Minimal to NON-Existence" of flaps on delta wings (which is, as shown, also rubbish for non-cannard aircraft).
Accel + Alt + VLO + DAS + MDF + Radial Distance = LIFE . . . Always choose Stealth
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vilters

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Unread post19 Aug 2018, 13:29

Enough to cook your potatoes on blue Mondays in the rain. LOL

First you ask a question, then you don't mike the answer, and start insulting. N :P I :P C :P E :P

OK, take some superglue and glue the things shut.

Could always use a welder too, but for that you need a red Wednesday morning in the shadow of a purple oak tree.

Could always train a dove to pull you around too, but only on even and orange Fridays.
=> They don't have a license for the rest of the week, only ducks do.

Oh, don't forget to deflate the tires to reduce weight and only let lightheaded pilots fly on dark yellow mornings.

And if you precharge the pitot system? ? ? You go faster. LOL.

And if the pilot manages to stay "in", he's not trying hard enough. LOL.

Euh, yeah, I cannna go onnna for a couple more days like this.

And if an elephant is chasing you? ? ? You are on a rollercoaster and should use wonder oil.

Stay off the booze and drugs man.
LEVCON's are one of the nicest inventions these last aerodynamic years and they trim like Wonder Woman without her bra.
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vilters

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Unread post19 Aug 2018, 13:37

PS; Still waiting for your example of a pure Delta that uses its trailing edge as flaps.
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vilters

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Unread post19 Aug 2018, 13:39

From your answer one by one:
Quote :
You seem to imagine that trailing-edge flaps are pitch trims--NO THEY ARE NOT.
Unquote.

Ok, what surface is used to trim then?
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vilters

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Unread post19 Aug 2018, 13:42

On your comment about pitch trim surfaces.

None of the newer aircraft have them. And new goes back 50 years or so. F-15, F-16, F-18, and the list goes on and on.

Trim is integrated in the software that controls surface deflection.
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vilters

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Unread post19 Aug 2018, 13:47

Your comment : Pitch trim does not reduce lift. Amaai, another one like this and it is Christmas.

The wing produces lift, and the slower you fly, the more you push the tail down and the harder the wing has to work to work. => Wing pulls UP and trim pulls Down. To maintain "total lift factor", the wing must work harder. (till it stalls)

But this last is open for discussion between sub and supersonic and depends on the relationship between center of gravity and center of lift, speed AOA and other.
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Unread post19 Aug 2018, 13:49

Next : You keep talking about trim surfaces as if you are dealing with a Piper or a Cessna.

Even the good old F-104, and F-4 and F-5 series did not have any trim surfaces any more.
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Unread post19 Aug 2018, 13:54

I hope the Indians know what they are doing, because integrating a LEVCON on an existing airframe is not an easy task.
ALL Flight control software has to be rewritten to use it to its full potential, and one of the finer tasks is high and low speed trim becasue whatever you do on the leading edge has an impact further down the wing.

It is a blue Sunday, so I am gonna go flying.
Have a nice day.
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