Thread closed for 24 hours to allow for cooling off.
F-15..you need to read the forum rules before you make any other post;
[h=3]Sinodefence forum rules of behavior[/h]
bd popeye super moderator
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Aerodynamics thread
- Thread starter siegecrossbow
- Start date
Thread closed for 24 hours to allow for cooling off.
F-15..you need to read the forum rules before you make any other post;
[h=3]Sinodefence forum rules of behavior[/h]
bd popeye super moderator
This thread is re-opened.
ALL Members abide by the rules of this forum:
Sinodefence forum rules of behavior
bd popeye super moderator
You're right on this one Eng, the LEVCON is not for pitch control, but to create additional vortex lift, as the center of pressure is moved fore and aft by the LEVCON, the canard/stabilator/elevator/elevons are "trimmed out" to maintain the desired airspeed/angle of attack. In addition aircraft employing OVT may employ that for pitch trim. The pitch trim required by the application of slats/flaps/LEVCONs can range from a miniscule amount to a great deal of trim, and those forces should be trimmed out rather than man-handled in order to minimize the likely-hood of a PIO. Even a Cessna 172, trimmed to 60Kts indicated airspeed with 40 degrees of flap, with the engine at idle, requires a great deal of "finesse" if you initiate a go around by the application of full throttle. As engine thrust builds quickly the flaps and elevators are "blown" and become much more effective in the prop-wash, the aircraft will immediately pitch-up, requiring a healthy application of forward yoke, as the trim is "milked-off". So LEVCON/Slats/Flaps are lift enhancing devices, not intended for primary pitch or roll control, that detail is left to the ailerons/spoilers/elevons for roll, and canards/stabilators/elevons for pitch control.
The highly swept delta wings usually have poor low-speed aerodynamic characteristics in example low lift/drag ratios and low lift curve slopes to compensate for the deficiencies of these wings, a lower sweep inboard wing section is employed such as in LCA and the LEVCON on PAKFA. these type of highly swept wing are susceptible to pitch and roll asymmetries in the high angle of attack flight regime. Vortex breakdown has adverse impacts on aerodynamic characteristics. Such as loss of lift, unstable pitching and rolling moment behaviour.
The strong effects of the leading edge vortex breakdown and the loss of lift on the wing sections due to flow separation, moves the center of pressure forward producing the pitch and roll asymmetries.
Then the LEVCON by selectively deflecting simultaneously in the same direction or deferentially, the lateral and directional control of the high-swept wing is improved, at high angles of attack, as well as the Sustained Turn Rate.
The LEVCON is a leading edge device that reduces the roll asymmetries of highly swept wing aircraft that are prone to leading edge flow separation and vortex breakdown and improves aircraft roll control, particularly at high angles of attack where conventional trailing edge surfaces lose effectiveness. The differential operation of the LEVCONs creates assymetricl lift increments on the wing to in order to generate lateral moments.
Reference
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>>>>>>>>>>>>> END MODERATOR'S COMMENTS AND INSTRUCTIONS <<<<<<<<<<<<<
Okay, F-15, listen up.
Compare what you said above:
F-15 said:
to this:
, a Master's Thesis by Alexander M. Benoliel at Virginia Polytechnic Institute.
On page 10, in Secion 1. Introduction to Low Aspect Ratio Platforms Designed for High-Speed Flight, we read this same quote.
Thesis by Alexander M. Benoliel said:
Then, three pages later, on page 13, in Section 2.1 Theorized Reasons for Pitch-Up we read the rest of your quote:
Thesis by Alexander M. Benoliel said:
F-15, are you Alexander M. Benoliel?
If you are, please tell us, and then you should cite your work and link to it.
I am guessing you are not, because you took these two exact quotes from this thesis, three pages apart, and strung them together like they were an individual thought of your own.
If you were going to cut and paste a quote from a publication like this, you absolutely should link it and quote it. Otherwise, the clear implication is that you are trying to make what you say appear as if though it is an idea coming from you.
I asked you to read the rules in a earlier PM to you. If you had, you would have read the following two rules:
Forum Rules of Behavior said:
If you are not the above mentioned author, this is a clear violation of those rules.
Forum Moderation will determine how to deal with this. if you are the Author, please contact myself or BD Popeye by PM within 24 hours and be prepared to prove it. If you do not respond accordingly, there will be forum discipline.
Hmmm...what are those footsteps I hear?
I believe Darth may be coming back very soon to see what's been going on here.
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i have modified it and quote him as a reference
I have okay quote him and re-write my message, but i was talking about
and he is talking about this
If you want me to put his link i have no problem, but my idea was different since i was talking about an inboard cut, not an outboard cut
i am talking about LCA
his idea is not exactly what i said, because he was talking about the outboard sections of the wing i am talking about the inboard cut at the leading edge of the wing plus the wing of PAKFA.
so be also keen to spot the differences
I have okay quote him and re-write my message, but i was talking about
and he is talking about this
If you want me to put his link i have no problem, but my idea was different since i was talking about an inboard cut, not an outboard cut
i am talking about LCA
his idea is not exactly what i said, because he was talking about the outboard sections of the wing i am talking about the inboard cut at the leading edge of the wing plus the wing of PAKFA.
so be also keen to spot the differences
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>>>>>>>>>>>>>>> MODERATOR'S COMMENTS AND INSTRUCTIONS <<<<<<<<<<<<<<<
F-15 is suspended for four weeks for plagiarism and taking issue with moderation warning him of the same on the thread. Both of which are violations of forum rules which he was urged to read and follow.
F-15, if and when you come back, be more polite, do not plagiarize, and follow moderator instructions according to forum rules.
>>>>>>>>>>>>> END MODERATOR'S COMMENTS AND INSTRUCTIONS <<<<<<<<<<<<<
Engineer
Major
The issue of contention isn't whether the center-of-lift shifts. The issue is whether LEVCON can be equivalent to canard in providing pitch authority, on top of providing vortex lift. As you have correctly pointed out, LEVCON is mainly for lift enhancement, not for pitch control. It is also plain clear from a simple law of physics that LEVCON with much shorter moment arm cannot compete with canard. Therefore, LEVCON does less than a canard, and cannot be said to be better. For someone to argue otherwise is like saying flap is better than canard, and I'm sure you will agree such argument is absurd.
Thanks again Eng, and I wish I were able to remain as kool as you brother when explaining this, you do have one convert here, as I loved the conventional lay-out, and failed to recognize the many benefits of the canard, and why they were so important to the J-20 until you layed it all out for me, I do appreciate your patience, and you are quite an outstanding teacher, I wish you could go to Oshkosh and observe all the amateur experimental aircraft, as I would love to hear your perspective on many of these aircraft.
Engineer
Major
You have read this argument of mine before, but I will write this again for the benefit of others. US experimented with thrust-vectoring on F-15, F-16 and F-18, but never decide to equip those aircraft in service with such technology. So, the Russian's emphasis with thrust-vectoring should be seen as nothing more than a marketing gimmick, especially when the Russians have a significant interest in making their older planes more sell-able.
Now, I am not saying thrust-vectoring has no purpose whatsoever. Thrust-vectoring can turn un-flyable situations into flyable ones. However, we should appreciate why those situations are un-flyable to begin with, and realize how it isn't a good idea to put the aircraft into those situations as a result. Indeed, exercises have shown that use of thrust-vectoring can led to a more superior aircraft being defeated.
So when someone tells me how much better an aircraft is with thrust-vectoring alone, that is no different than telling me that the same aircraft is aerodynamically complete garbage.