Aerodynamics thread

delft said:

I would always be afraid of loosing kinetic energy and so perhaps be forced to dive at a moment your opponent can expect. The Harrier could use these manoevres because at that time missiles were not able to turn as fast as they are now so sacrificing speed it order to get into a good firing position made sense. I'm afraid that this has become useless by now.

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Not necessarily. It all depends on the situations and the kinetics/dynamics of that situation at the particular time.

It is always good to have tricks up your sleeve to apply when they could be beneficial.

Such a maneuver as this would require particular parameters...and if the pilot was put in that position...where it would make sense and potentially be a game changer...having it available could be useful.

They would of course have to be trained on when to use it...when and where it would make sense.

Jeff Head said:

Not necessarily. It all depends on the situations and the kinetics/dynamics of that situation at the particular time.

It is always good to have tricks up your sleeve to apply when they could be beneficial.

Such a maneuver as this would require particular parameters...and if the pilot was put in that position...where it would make sense and potentially be a game changer...having it available could be useful.

They would of course have to be trained on when to use it...when and where it would make sense.

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Right, and if you had a bogey on your six rolling inverted and slighty nose down you wouldn't necessarily lose energy if you popped those nozzles down?? the wild card is the lift fan door, and we're fairly certain that is speed limited??? possible to 200 to 250 knts????

somebody knows at least some of these things??? they prolly can't or shouldn't tell? LOL

IIRC Harrier was not designed with such practice in mind and it was developed years after the first flight of the first P.1127 Kestrel. I think that designing the F-35 family was difficult enough without such considerations.
You must also expect that pilots will have trained in simulators to counter any special manoevres opfors are aware of and you must find it difficult to keep such manoevres adequately secret while still providing your pilots with the necessary training.

Air Force Brat said:

Right, and if you had a bogey on your six rolling inverted and slighty nose down you wouldn't necessarily lose energy if you popped those nozzles down?? the wild card is the lift fan door, and we're fairly certain that is speed limited??? possible to 200 to 250 knts????

somebody knows at least some of these things??? they prolly can't or shouldn't tell? LOL

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Okay, now that the Mig 1.44 is on display at MAKS 2015, Mig has announced that they will be "working" on a middleweight fighter based on 1.44, for you gents that want to play photo-shop or CG games, show me an updated 1.44? anybody up to that?

Feel free to beef up the gear and add a tail-hook!

China is now is possession of almost mature TVC-technology with the WS-10B TVC variant. I know you guys like to deride me over weird projections, but how close are we now to a J-20 running TVC engines? With the J-11Ds testing TVC, it would probably be 2-3 years before the J-20s test them, and we'd probably be another 5 years before it becomes standard. However, with the absurd pace of Chinese development, I can actually imagine tailfinless J-20s by 2025 now. That'd be a mean surprise to F-22s.

FYI, yes, TVC has penalties in terms of weight. With 2D TVC, it also has penalties in terms of fuel consumption (the change from a circular to a rectangular exhaust consumes part of the thrust). But Chinese TVC is 3D, to begin with, and both the J-20 and the J-10 are long-coupled or semi-long-coupled canards, where the distance of the coupling benefits more in terms of BVR instead of WVR. Think Rafale and Eurofighter; the Eurofighter had a TVC system proposed, but later mooted, but the Rafale has never even considered TVC. That's because the Rafale is a close-coupled canard, for which the TVC won't give any benefits, while the Eurofighter is a long-coupled canard.

Inst said:

China is now is possession of almost mature TVC-technology with the WS-10B TVC variant. I know you guys like to deride me over weird projections, but how close are we now to a J-20 running TVC engines? With the J-11Ds testing TVC, it would probably be 2-3 years before the J-20s test them, and we'd probably be another 5 years before it becomes standard. However, with the absurd pace of Chinese development, I can actually imagine tailfinless J-20s by 2025 now. That'd be a mean surprise to F-22s.

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Well, I'm glad you're prepared LOL, so that's what happens when you eat sauerkraut and brats so late at night with your "Heavenly Hash" ice cream???

So OVT??? and as Jeff politely states "we'll just have to wait and see??? I'm NOT buying it, the Eng is "dead set" again it to start with, but maybe you R right about OVT, it does work well on the Raptor, T-50, and gives your average big hog Flanker a "kick in the butt", and makes a real airplane out of it!

Tailless, NYET KOMRADE! NO ONE or their Dog is flying a tailless fighter, I just don't think with fighter doctrine where its at?? that anyone wants to give up that much maneuverability for a little more L/O profile, and look at the J-20, not only substantial all flying rudder-vators, but two very large ventral fins to maintain directional stability. Looks kool and works on a bomber, but a fighter is a whole nother animal, when we see the first tailless, OVT equipped fighter aircraft in production, defeating F-22s mano a mano?? please get back to me, and I will offer you an "OFFICIAL" AFB full apology??? but don't hold your breath on that one.

Inst said:

FYI, yes, TVC has penalties in terms of weight. With 2D TVC, it also has penalties in terms of fuel consumption (the change from a circular to a rectangular exhaust consumes part of the thrust). But Chinese TVC is 3D, to begin with, and both the J-20 and the J-10 are long-coupled or semi-long-coupled canards, where the distance of the coupling benefits more in terms of BVR instead of WVR. Think Rafale and Eurofighter; the Eurofighter had a TVC system proposed, but later mooted, but the Rafale has never even considered TVC. That's because the Rafale is a close-coupled canard, for which the TVC won't give any benefits, while the Eurofighter is a long-coupled canard.

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So, if the Raptor's rectangular nozzles are as inefficient as you state, why does it have the fastest "supercruise" on the planet?? Why does it have the highest operational altitude of any operational fighter aircraft??

The J-20's large, all flying, extremely long control throw canards are very effective and in my personal observation are very likely to afford extremely rapid pitch transitions, positive or negative, likely negating much of the advantage of OVT, without the weight, maintenance, and increased fuel consumption of OVT?

Boeing and Lockheed are moving towards tailfinless. Boeing, in particular, uses a canard design for their F/A-XX design. The concept is that you use 4 TVC nozzles to compensate for the loss of tailfin control, allowing you to reduce drag and RCS. I think the J-20 is suitable for such a mod; 2 TVC engines + 2 canards may allow the J-20 to achieve controllable flight without tailfins to provide yaw.

The F-22 is the fastest, but that's because of its low drag-coefficient as well as its powerful engines. I read somewhere that the 2D TVC cuts the F119 engines' thrust by 17%. Incidentally, if you add the thrust back in, you get the 180kN that was originally projected for the F-35, and if you work with a 160 kN base, you get the 190 of the current F135 engine.

The debate is more whether the Chinese 6th gen will be a canard fighter. The problem is that canards have trade-offs; they increase RCS to a degree, as well as drag. The best option is either the Lockheed-style TVC-control only aircraft, which allows superlatively low drag and minimized RCS, or as I would prefer, a 6th generation tailfinless LEVCON. Such an aircraft would have the advantages of a 6th gen canard fighter; i.e, it's not that reliant on TVC, so if TVC fails, you still retain control authority through the canards, as well as some of the advantages of 4x TVC vs canards; LEVCONs present less aerodynamic control relative to canards, but they also reduce drag and RCS, when compared to canards proper. If such a path were taken, research on LEVCON control systems should begin immediately, perhaps with the J-11 series or the J-31 series.

In any case, as long as the Russians get enough money to fuel their military-industrial complex (and with oil likely to be between 60-80 in the long-term, probably not), they will probably give us a LEVCON 6th gen. It would be better for the Chinese to do it, however, because the Chinese are not short of money and have the R&D complex to take such a project through.

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Also:



It's the drag advantage that will keep tailfinless aircraft alive even if Russian photonic radar renders stealth obsolete.