Cornering speed

The F-35 compared with other modern jets.
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steve2267

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Unread post28 Apr 2017, 16:39

Do we yet know what the F-35's cornering speed is?

As I recall, the F-16 has a cornering "plateau" starting around 350kts. To what does that extend? 400kts?

Does how fast or slow an aircraft corners at matter? Is it preferable to have a lower cornering speed or a faster one? Obviously, if you can pull 9G at 300kts, you will turn tighter (smaller radius) than if you can pull 9G at 350kts. Also, the turn rate will be higher. But the slower you go, you will need a higher angle of attack to achieve that same load factor, and the drag will quickly increase with increasing alpha.

But speed is life. (Or so I have read.) Would you guys that have been there, done that, prefer to be able to pull 9G all day at 400kts? Or at 350? 300? 250?

For argument sake, lets say you had a plane that could turn all day at 9G at 150kts (hypothetically speaking). Your turn radius would be tiny, your turn rate would be awesome, but when you come out of the turn, you'd still only be doing 150kts. Haven't you just made yourself a grape for anybody else in the area?

The picture that is forming in my head is that I'd like to be able to pull 9G "all day" somewhere in the 325-400 kt range, but if I need to, I can trade airspeed for increase angle of attack to generate higher turn rate to get my nose around quicker, but I want a monster engine to get my smash back quick when I unload.

Reading between the lines, I am guessing the F-35 engineers have managed to pull something like this off. But with no aerospace press smart enough to ask the pilots, and no E-M diagrams about, it is just a hunch.

(I realize this is 4th-gen thinking, but I'm an aero guy wondering / marveling about what new tricks the F-35 designers have pulled off.)
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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Unread post28 Apr 2017, 17:08

Google HAF F-16C Flight Supplement. You can find F-16C Block 50/52 E-M diagrams with the CP in there. The earlier Vipers needed less speed I believe, since they were lighter (and the A models had the less draggy NSI). The Block 25,32 also had the NSI but only had -220s.


F-35's Corner Velocity is probably still classified.
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Unread post28 Apr 2017, 18:40

The earlier test 240-3 configuration corner speed-

370 knots at 15,000 feet.
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Unread post28 Apr 2017, 19:55

fbw wrote:The earlier test 240-3 configuration corner speed-

370 knots at 15,000 feet.

True or indicated? :wink:
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Unread post28 Apr 2017, 20:13

sprstdlyscottsmn wrote:
fbw wrote:The earlier test 240-3 configuration corner speed-

370 knots at 15,000 feet.

True or indicated? :wink:


If it was from an E-M diagram, I assume they'd be quoting true airspeed (edit- no calibrated). The quote from "F-35 combat skills analysed", no idea.
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Unread post28 Apr 2017, 22:55

I don't really care what corner airspeed is......350, 400, 450, doesn't matter that much, though it is interrelated to the value that I do care about, which is the rate band. If you look at an E-M diagram, this is where Ps=0, and you are sustaining energy and turn rate at a specific load factor. I think OP might be confusing these concepts, as corner airspeed is just an instant in time........I apply max G at this small window of airspeed values, and I get the greatest instantaneous turn rate, which quickly diminishes as I bleed energy. Conversely, if I am in my rate band, at something less than the load limit as indicated by the Ps=0 curve on the E-M diagram, I can maintain that (somewhat diminished) turn rate indefinitely. The wider and flatter the band, the more options I have in a fight. If I have a better average rate in my band than my adversary, I will have an overall advantage in a rate fight/typical BFM engagement. The more compressed the +Ps curves are to the Ps=0 curve, the better my energy addition will be, which is a function of higher T/W, and will also yield an overall advantage. So those are the things that would be desirable to me.
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Unread post28 Apr 2017, 23:48

35_aoa, thank you for the explanation. I am still processing all this. I think I understand what you are saying, but I am in the car (wife driving) and don't think I will be able to post an E-M diagram for discussion at the moment.

That being said, for discussion sake, if you could maintain a load factor of 9g (Ps=0) at 375kts (same altitude, say 15K ft), but I could do the same at 300kts, am I not going to be able to outturn you? (both higher turn rate and smaller turn radius?)
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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Unread post28 Apr 2017, 23:59

steve2267 wrote:35_aoa, thank you for the explanation. I am still processing all this. I think I understand what you are saying, but I am in the car (wife driving) and don't think I will be able to post an E-M diagram for discussion at the moment.

That being said, for discussion sake, if you could maintain a load factor of 9g (Ps=0) at 375kts (same altitude, say 15K ft), but I could do the same at 300kts, am I not going to be able to outturn you? (both higher turn rate and smaller turn radius?)

That is kind of like asking if 3 is more than 2. The answer is yes, but if you can sustain 9G at 300, but 7G at 400, 5G at 500 etc and he can sustain 8G from 300 to 500 then he has more options.
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Unread post29 Apr 2017, 00:11

sprstdlyscottsmn wrote:That is kind of like asking if 3 is more than 2. The answer is yes, but if you can sustain 9G at 300, but 7G at 400, 5G at 500 etc and he can sustain 8G from 300 to 500 then he has more options.


At least I am asking if 3 is more than 2, rather than trying some Solomonesque argument that 2 is greater than 3. :P

So sprstdly, in your example, I have an advantage at 300 (9G), but he would have an advantage at 400 (8G). If this is guns-only, then I should be able to outturn / turn inside him, but if he keeps his speed up at 400kts, I might not be able to close. Alternatively, if he is getting ready to saddle up on me, I should be able to slow down / turn inside him, forcing him outside my turn. Then perhaps I can try to reverse into him. If he gains energy better than I, when I reverse, he should be able to unload and extend away from me. (Of course, this thinking is 2D / planar and does not take the vertical into consideration.)
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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Unread post29 Apr 2017, 00:32

Haha no prob. Find me a jet with a Ps=0 curve at 9G, at any airspeed band/plateau, and I will trade my life savings, wife, child, etc to fly it. A slick block 15 viper at about 10k feet or below feels like it is that jet, but I am pretty sure even it is a little less than that (maybe 6-7G sustained until the tank runs dry).
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Unread post29 Apr 2017, 00:54

35_aoa wrote:Haha no prob. Find me a jet with a Ps=0 curve at 9G, at any airspeed band/plateau, and I will trade my life savings, wife, child, etc to fly it. A slick block 15 viper at about 10k feet or below feels like it is that jet, but I am pretty sure even it is a little less than that (maybe 6-7G sustained until the tank runs dry).


Not being a dimwitted aerospace / defense reporter with a pair of pillows, I've never gotten a free Viper ride. So I have no idea what 9G is like. But I've read it is pretty punishing.

Would you make the same trade if you could air brake to 250kts likkety split, twirl around at 7G (Ps=0), then hit the go switch and be magically back at 400-450 kts?
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.
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Unread post29 Apr 2017, 06:51

steve2267 wrote:At least I am asking if 3 is more than 2, rather than trying some Solomonesque argument that 2 is greater than 3. :P

So sprstdly, in your example, I have an advantage at 300 (9G), but he would have an advantage at 400 (8G). If this is guns-only, then I should be able to outturn / turn inside him, but if he keeps his speed up at 400kts, I might not be able to close. Alternatively, if he is getting ready to saddle up on me, I should be able to slow down / turn inside him, forcing him outside my turn. Then perhaps I can try to reverse into him. If he gains energy better than I, when I reverse, he should be able to unload and extend away from me. (Of course, this thinking is 2D / planar and does not take the vertical into consideration.)

No worries, you are asking the right questions (or at least are thinking the right direction). In a purely horizontal fight it would take you at LEAST 5 seconds of no turning at all to accelerate by 100knots, and that is with 1G acceleration, to MATCH the speed of the guy who just blew by you. Could you stay defensive and turn inside him all day in a one circle match? Sure, but why would he fight that way. He would use HIS advantage and turn away to create separation and turn back around after doing so if forced to stay horizontal. The reality is he would make his turn while climbing, thus shortening the horizontal aspect of the turn (tighter lateral radius, still lower rate) but giving more options as now he is perched X00 feet above you. This type of discussion is not too dissimilar to F/A-18A vs F-16A. Which one is better in a dogfight? It depends on how well each pilot flies their plane. In a guns only BFM the F/A-18 SHOULD be able to force the overshoot nearly every time, and likewise the F-16A SHOULD be able to extend laterally or vertically at will to escape so it boils down to who makes the first mistake. If the Hornet driver tries to force the overshoot too soon the Viper pilot may climb instead, such that they both end up in a similar lateral position and speed but one aircraft is hundreds of feet higher and can accelerate more quickly in a gentle climb or a turn than the other can do in a straight line.
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Unread post29 Apr 2017, 08:30

steve2267 wrote:
Does how fast or slow an aircraft corners at matter? Is it preferable to have a lower cornering speed or a faster one? Obviously, if you can pull 9G at 300kts, you will turn tighter (smaller radius) than if you can pull 9G at 350kts. Also, the turn rate will be higher
Turn rate will be Lower only turn radius will be smaller at 300kts and 9 Gs versus 440 kts and 9 Gs.But with a lower wing loadings it will be an additional momentarily advantage .Faster corner speed is better than lower, because turning you spend kts but higher corner speed allow you to turn climb at a value bigger than enemy whit a lower corner speed .Dogfight is nothing else just to place yourself in the patch of sky were you employ weapons .Turning at higher Gs is fatigue induce process.Not desirable .If you could destroy enemy whitout turning fight do it .The 9 Gs for 1/2min.is hard thing to do. Pilots not always are ready to perform at max. capacity .The same for the planes .Messerschmidt 190 of Germans WWII turn better than F16 but will not be able
to be winner in the fighting.
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Unread post29 Apr 2017, 13:16

35_aoa,

As Naval Aviator, I was wondering if you could give your perspective about the F/A-18C vs Block 15 F-16A once they hit the merge. I understand that they like to fight at different speeds. And I also know that the F-16A has a STR and Thrust to Weight advantage, while the Hornet probably has a small turn radius advantage at low speeds and obviously far better high Alpha capabilities.

It seems that the current Viper (the Block 50/52) has lost some of its "phone booth" fighting capabilities because of all the weight growth. I was just figuring that even though the Block 15 bleeds some airspeed, the fact that it is over 3,300 lbs lighter, it would be a more dangerous opponent for a F/A-18C pilot in a close in angles fight?
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Unread post29 Apr 2017, 15:00

The largely academic discussion of EM diagrams is but one (and minor at that) starting place for acquiring BFM skill. EM diagrams actually make more sense after one has acquired some BFM experience because they help one translate what one experienced in the jet to what the numbers said the jet would do, particularly when one starts dissimilar training.

The most dominant (notice I didnt say "absolute") predictor of outcome in BFM is not the jet, it is the pilot. Some guys are more natural BFMers; some -- who are otherwise terrific aviators -- dont do 3-dimensional maneuvering worth a crap. However, skill is important but experience matters most, and some old farts in nominally inferior jets (comparatively, using EM diagrams) have handed SH teen series guys their asses for decades, That's how/why A-4s snd F-5s have remained in the adversary business all this time. Technology changes stuff (e.g. Raptor) but some things don't change much...

In my experience, well-flown Hornet always a more challenging BFM opponent than Viper. All that sustained performance often works against them. Sometimes ya gotta learn to slow down... :salute:
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