ACM question - one circle flow

I've read "Fighter Combat: Tactics and Maneuvering" and tried implementing some of the advice there in game, mostly in squadron practices. I was revisiting circle flow tactics when I spotted something that I had used before but now don't understand why it makes sense.

On page 101, under similar aircraft guns only, it says that if you're going for the angles fight you should turn into the bandit, then if he responds in kind, reverse your turn to go for one-circle flow. This is logical.

Then it says you should turn nose low and use gravity to avoid bleeding too much speed going for a max-G, min-radius turn. This makes some sense, but isn't one-circle flow all about reducing radius? In which case, why doesn't it make more sense to go high, deliberately reduce speed while preserving energy and reduce your turn radius without pulling max G?

I assume there's a reason the book doesn't recommend it, I just want to understand the physics at play as to why a low yo-yo is the correct move here, not a high yo-yo.

I think the comment about the bandit reversing is if he reverses to a single circle radius fight. An angle fight would be a rate fight in Nato nomenclature as in you are maximizing your angular rate of turn.

Most fights where you both turn towards each other which is a natural 1v1 entry will be a rate fight and normally will involve a descending turn at corner speed to maintain best rate.

If you want a rate fight for instance F16 vs F18, then if the bandit reverses from the natural 2 circle entry then you also reverse and keep it 2 circle.

Radius fights as you point out normally involve a climbing turn to reduce speed and hence radius.

May even involve use of speedbrakes depending on energy level and weapons.

If I am in an F18 I nearly always want a radius fight so I will watch and reverse as required to make sure it goes Radius. Last guy to reverse has decided the fight .

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That's exactly what I thought.

But here's the diagram I am confused about. The text recommends reversal at time 3 to keep the fight 1 circle... and then advises a descending high rate turn in what is clearly a radius fight.

Yep agreed slightly weird he is keeping his lift vector on the bandit so if his speed was already low pre merge then the descending turn would make sense. The bandit keeps going down in a rate fight entry in the picture so it makes sense but the bandit is being dumb.

We always used to lock the guy head on to see what his energy state was just in case he was coming to the merge at 200kts but kept his wings back to try and fool you.

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One circle and two circle are mostly about maximizing rate (or minimizing time to turn). Radius is usually not much of a factor unless you're in scissors. Angles fighter benefits from the one circle fight as he may rate better than his opponent. Energy fighter enjoys two circle as distances are greater and more opportunities for a head on engagement.

I believe the low maneuver is to trade energy for nose position to threaten the opponent most immediately. The angles fighter benefits for a slower fight anyway and so encouraging more defensive turning is only a benefit.

Sorry to disagree but one circle is a factor at the merge. F18 is a radius fighter and nearly always wants to force single circle at the merge. An F3 can get 1st shot on an F15 if he lets you go single circle. Because of that we always went single circle at the merge with a gen 4 fighter ( tbh we had already messed up if we end up in the merge but that's another story).

Single circle radius fights are definitely not only about scissors.

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Well, I used the tactics described in some practice fights and was able to gain an advantage in both 1-circle and 2-circle by going nose low. I was however deliberately merging at corner speed while the other guy admitted he was too fast. In the excitement I forgot to try nose-high in 1-circle, actually nose low felt intuitive because I was pulling a lot of AoA and getting buffet and wing rock (F-14), which nose low saved me from. So maybe if I went high I would have just stalled out and flopped about instead of gaining an advantage. I'll remember to actually try it next time.

The other thing that's odd is the book talks about gaining as much energy as possible into a merge, but in something like a Tomcat if you "zoom climb to slow down to corner speed" you'll be in the stratosphere. With powerful jets it seems you actively want to dump energy going into a merge if you plan to turn, again counterintuitive.

Yes there is an optimum speed for the merge depending on the thrust to weight/drag ratio. F14 bleeds pretty fast but if you are too fast then you will be to far above corner speed. While there are a few other factors involved I normally try and do about 0.9 in a 14 as it seems to be a fair compromise.

TBH I fly all the modern aircraft in DCS and while the F14 is my favourite as long as I have a RIO or a pilot with the group I fly with we accelerate to M.9 on the commit as an SOP. If we mess up and end up in a merge it gives you a pretty good starting point whatever the aircraft.

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The tactics in the book were largely written with the assumption that no aircraft can sustain corner speed. Not even the F-16 could really do that at the time that book was written. Maybe the Block 50 F-16C and F-14D changed that reality. So going nose low to keep max turn rate is critical to winning the turn fight. If the fighters are otherwise equal, the one that doesn't go nose low, will lose angles, while the nose low fighter will still have the energy to pitch up for the shot after gaining the advantage.

If the aircraft in question can sustain best cornering speed, there is absolutely no reason to go low. If their specific excess power is such that they can sustain best cornering speed while climbing, then the advice would be the opposite: go nose high to maintain optimum turn rate while gaining altitude.

In a fight between an F-15A and F-4E, the F-15 has a problem: no high lift devices and pretty much the same max-g as the the F-4E. But the F-15 can pull that 7g while climbing while the F-4E has to stay level or go nose low. To an extent, the F-15A could do this to the F-16A: the F-15 couldn't turn with the F-16 on the level, but it could climb while pulling 7g, which the F-16A could not. Gunsight footage from the 1970s shows this as the F-15 slides out of the gunsight in the direction of more altitude.

So the principles of the book are generally correct, but you have to look at the actual capabilities of the aircraft and realize how they change the application of those principles beyond simply deciding whether an aircraft is an energy fighter and/or angles fighter or neutral relative to a given opponent. Thrust to weight has come up just a bit as well as new tech like vector thrust that slightly changes the available options.

I think there is some confusion here.

Corner speed is at maximum rate (and so you are also at max G load).

Sure you can sustain the same speed if you relax on the stick, but then it isn't corner speed anymore.

There are also speeds & altitudes where you can sustain max G load, but you're so fast you aren't at corner rate either and turning more slowly and wider.

I think we've migrated off the point my original question. Of course different fighters may be able to do different things while sustaining corner speed.

But shouldn't radius be minimised in this case? And doesn't that happen at a speed significantly below corner speed anyway, and at lower G? Why pull tons of G and go nose low to keep your speed, instead of going high to slow down and reduce radius? Even if he goes around his turn faster than you, isn't the whole point of 1-circle geometry that you have the advantage even as a slower fighter as long as you've turned tigher?

My guess from that bit of text is this - whenever the "angles fight" is discussed, the book always emphasizes how important it is to maintain minimum vertical maneuvering speed to threaten the boogie should he choose to go vertical. It's harder to do that if you go nose high and further bleed speed in an attempt to reduce your turn radius. If you do go vertical while turning hard, while the boogie follows you without pulling as hard, then you play into the energy fighter's hands if that makes sense. At least, that's my interpretation of it :)

You are indeed correct that radius is generally minimized below corner speed (e.g. page 392) and that 1 circle fights benefit minimum turn radius over maximum turn rate (e.g pages 79 and 80) though.

If you look carefully at the physics involved, you can see that below corner speed your turn radius is almost constant while doing a lift limit turn. So as long as you stay slower than corner speed and faster than minimum radius speed your radius is going to be pretty close to the minimum.

While the radius may be fairly constant the lack of forward progress at a slower speed helps you get your weapons on earlier. In practice you slow down a lot more than just below corner speed in a single circle fight.

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My guess from that bit of text is this - whenever the "angles fight" is discussed, the book always emphasizes how important it is to maintain minimum vertical maneuvering speed to threaten the boogie should he choose to go vertical. It's harder to do that if you go nose high and further bleed speed in an attempt to reduce your turn radius. If you do go vertical while turning hard, while the boogie follows you without pulling as hard, then you play into the energy fighter's hands if that makes sense.

If you look carefully at the physics involved, you can see that below corner speed your turn radius is almost constant while doing a lift limit turn. So as long as you stay slower than corner speed and faster than minimum radius speed your radius is going to be pretty close to the minimum.

Yes, thank you, that's what I was looking for. Those pieces of information together do make it make sense. :) There's still the fact to consider that you would be above him and inside his turn, but I can see that with a significant loss of turn rate (slower speed) without a further radius gain, you would struggle to gain a further advantage from that position.

While the radius may be fairly constant the lack of forward progress at a slower speed helps you get your weapons on earlier. In practice you slow down a lot more than just below corner speed in a single circle fight.

With all aspect missiles yes, but the part of the book I was referring to is about guns only. In guns only, it makes a lot less sense to burn all your energy for a shot you might not even get, then have the guy energy fight you at his leisure because you can't properly threaten him if he sees what you're doing and just extends.

Well if we're going that way, if you assume the angles fighter carries all-aspect missiles then going 1 circle doesn't even make sense because by the time your nose comes around you might be within min-range and not be able to fire.

Yes, thank you, that's what I was looking for. Those pieces of information together do make it make sense. :) There's still the fact to consider that you would be above him and inside his turn, but I can see that with a significant loss of turn rate (slower speed) without a further radius gain, you would struggle to gain a further advantage from that position.

The easiest way to see this in action are the turn radius lines of an EM diagram. Start at a Ps: 0 point near one of the radius lines. You go a little bit faster (to the right), pull a little bit more G, radius stays the same while resulting rate goes up. Select a higher descent rate in ft/sec to increase your actual Ps, you pull a bit more and your radius goes down while similarly increasing your rate of turn. So you can, in fact, descend with a higher G turn and maintain the same (or better) radius than the bandit with a higher turn rate. The trick is in moderating how much you lose in altitude versus how much you gain in G.

If you look carefully at the physics involved, you can see that below corner speed your turn radius is almost constant while doing a lift limit turn. So as long as you stay slower than corner speed and faster than minimum radius speed your radius is going to be pretty close to the minimum.

Hmm don‘t think you can make such a general statement.Highly depends on which aircraft we are talking about.

If you look at the various EM diagramms floating around, there are quite a few aircraft ( only talking jets now) where the speed for minimum radius is quite a bit below corner speed and more importantly, the difference in turn radii is significant, eg. radius being halved or more at the lower speed.The lower speed and decreased turn radius seems to me what counts in a 1circle fight.

So far I m also problems understanding the advice of the mentioned book.

Kind regards,

Snappy.