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#3880085 - 12/19/13 04:31 PM How to perform Lag Displacement Roll Attack?  
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Laurwin Offline
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I never even knew about this basic fighter manouver before reading the "In pursuit: online pilot's guide for air combat." The lag displacement roll manouver...

From the picture in the textbook, this tactic looks like it could be plenty effective when done right. Yet I don't think I've ever seen this tactic being used on me in online combat, or I've never used it myself in the game IL-2 1946. And yet it's considered a BFM manouver?! Funny that!

I saw the picture of this BFM manouver in the free online version of In Pursuit, about how you're supposed to perform the lag displacement roll manouver on the offensive.

On page 94, picture of lag displacement roll engagement in pursuit free online pdf The following questions are mainly in the interest of the air combat game IL-2 1946. The questions are intended for propeller aircraft air combat.


1. people seem to confuse this manouver with some other manouver like high yoyo. Apparently they are two entirely different manouvers basically?


2. This manovuer is really hard to visualize for me, what exactly is the attacker is supposed to do? (with the rolling part of this attack)


3. It would maybe help to understand, if you had a textbook example, which was worked into a 3D animation (or game video for that matter). I tried to search youtube today (had a really busy day inreal life couldn't search too well), but I didn't really find much understandable examples of lag displacement roll attacks.



4. Let's assume that the attacker (you), roll away (!), from the enemy (who is break turning)

Isn't this an obvious question but basically, at that moment in time, when you roll away from the bandit, the attacker cannot see bandit anymore? The defender could easily stop turning predictably like that because attacker can't see him anymore?


5. does the manouver work even if the enemy makes a break turn unsustainably? (as opposed to sustained turn, which I suppose would be better for the bandit, in theory, for energy retention purposes, but you never know)

After all, unsustained turn makes a really tight turn radius, I was wondering if the lag displacement roll allows to adjust to that turn radius?

Last edited by Laurwin; 12/19/13 04:31 PM.
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#3880168 - 12/19/13 06:21 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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damson Offline
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This maneuver to me looks like High yo-yo but instead of rolling into your opponent's turn after climb you roll the other way while maintaing visual contact (in high yo-yo he would crossed under your fuselage when you turned into his turn).

From attacker's point of view it might look like this:
- attacker (A) in lead pursuit closes to the defender (D) quickly
- (D) tries to increse angles on (A) by starting a turn into (A) (i.e. right)

...(D)..
.../....
../.....
./..(A).
/....|..
.....|..

- (A) having (D) on his left, starts pulling up while rolling left, maintaining his line of sight on the (D)
- (A) while rolling puts it's lift vector on (D) bringing him to pure pursuit position behind (D)

So it's basically lag roll.

to illustrate:


Last edited by damson; 12/19/13 06:28 PM. Reason: added link to a video
#3880212 - 12/19/13 07:12 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Laurwin Offline
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When does the attacker, start climbing vertical? Does it have to happen, when the defender is still on the left side of the attacker's nose position (this is happening during the defender's break turn to the right, from attacker's persepctive)?


How many rolls does the attacker do during the attack (or do you roll slower, but only one full rotation ?)
This is for the diagram that you pictured.

Where to, does the barrel roll, displace your own aircraft (judging from above perspective, like a map perspective, are you still going in the same heading where you started from, when you are barrel rolling and climbing?)

When you are on the final gun run, to kill the defender (out of the barrel roll), how do you prevent going too fast (so that you don't overshoot "from under the bandit", so that attacker is able to pull enough elevator to pull lead pursuit on the defender, and kill him with gun)

After trying this situation out myself with paper planes folded out of A4s (embarrassing I know) it seems that Ive gained slightly more understanding towards the manouver, but I don't understand it completely LOL confused

#3880216 - 12/19/13 07:18 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Laurwin Offline
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I have actually done basic lag roll DEFENSE situation online in IL-2. It was me with spitfire mk8, against bf-109 (I ended up defeating the attacker), but I have never used lag roll for attacking like that example in the textbook!

#3880217 - 12/19/13 07:21 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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GrayGhost Offline
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Originally Posted By: Laurwin
1. people seem to confuse this manouver with some other manouver like high yoyo. Apparently they are two entirely different manouvers basically?


They're used for different purposes usually, but they're very similar. Some BFM maneuvers can be similar enough to be confusing. Think in terms of fluid maneuvering and why you are doing this particular maneuver, not in terms of the maneuver being this or that.

Quote:
2. This manovuer is really hard to visualize for me, what exactly is the attacker is supposed to do? (with the rolling part of this attack)


It can be a small barrel roll, but don't think of the aerobatic maneuver - you don't need to complete some perfect barrel roll, the important thing is to use it to maintain sight, gain correct spacing and get inside bandit's turn circle.

Quote:
3. It would maybe help to understand, if you had a textbook example, which was worked into a 3D animation (or game video for that matter). I tried to search youtube today (had a really busy day inreal life couldn't search too well), but I didn't really find much understandable examples of lag displacement roll attacks.


Because these maneuvers are fluid. Textbook maneuvers are meaningless as anything but example except when a bandit flies so nice for you that you can perform a textbook maneuver. There's nothing saying you have to complete a maneuver start to finish, you can interrupt it and start another, or change it up in some other way. Besides, why are you trying to use a lag displacement roll? It is tactically sound in your situation? That's the real question you have to ask. Having said that, why are you using a maneuver because it has a name?
In flight, everything is done according to lead/lag/pure pursuit with your flight path and lift vector. Every maneuver you do gains energy, loses energy or is neutral, and it may gain or lose forward speed as well. For example, you can do a barrel roll and not slow down one bit, but the guy beside you going straight at 500kt will shoot out in front of you - why?

Quote:
4. Let's assume that the attacker (you), roll away (!), from the enemy (who is break turning)

Isn't this an obvious question but basically, at that moment in time, when you roll away from the bandit, the attacker cannot see bandit anymore? The defender could easily stop turning predictably like that because attacker can't see him anymore?


Never count on the bandit losing sight. And if he appears to be a juicy target, always count on his wingman bagging you.

Quote:
5. does the manouver work even if the enemy makes a break turn unsustainably? (as opposed to sustained turn, which I suppose would be better for the bandit, in theory, for energy retention purposes, but you never know)


It depends ... mostly on how you perform your flying.

Quote:
After all, unsustained turn makes a really tight turn radius, I was wondering if the lag displacement roll allows to adjust to that turn radius?


No, your flying and BFM skill allows you to adjust for that with your pursuit curves. Everything is about pursuit curves. It doesn't matter what the maneuver is called, it's executed with relation to the bandit which is why it will always depend on pursuit curves. If you're waiting for more than half a second to see what the bandit does so you can react, you're too late. This observation and reaction is constant, there's no definitely 'ok this, then this' point, you are constantly flying. Of course, a cooperative bandit can make things easy for you. But that's a cooperative bandit.

Last edited by GrayGhost; 12/19/13 07:23 PM.

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#3880235 - 12/19/13 07:43 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Laurwin Offline
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well yea, I asked because...

a) It's classified as a basic fighter manouver, and I didn't grasp the manouver simply by reading/looking at picture. So, I decide to ask for more...

b) even though it was a specific case, I wanted to understand why it works like that, in that specific case (admittedly this discussion has so far centered on the theoretical side, without specific 1v1 matchup of real aircraft, and input values)

c) how would the textbook case, be countered by the defender, in that specific case. Should the defender just keep turning like that, to the right?

d) e.g. what if in that textbook case, the defender unloaded G on his own aircraft, stopped turning to the right, and simply extended for a while?

e) If in fact, the defender decides to extend instead of continuing break turn all the way to the right, and also, when attacker starts coming down. What would the end positions look like?

Could the end position resemble the starting position, from which the encounter started in the first place?

#3881369 - 12/21/13 07:01 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Hey Laurwin,

There are a couple of obstacles you're facing in understanding the displacement roll attack (From here on out, I'm just going to call it a Barrel Roll Attack or BRA since, realistically, they are the same animal with little variations).

The first goes a bit along with what Gray Ghost was saying in that you are (understandably) mixing in the maneuver with the situations, outcomes, and counters of what precedes it and what follows. The BRA, just like all the BFM "maneuvers" isn't really a maneuver as such as it doesn't need to be "completed" to have its desired effect and it isn't "one size fits all".

Let's try an example and maybe some of your questions will be answered in the process.

The fighter (attacker) sees the bandit (defender) more or less on the same heading as the bandit, but displaced over to the left or right and with a significant amount of closure and relatively close...let's say with the bandit at the fighter's ten or two. If he didn't have a ton of closure, the fighter could just slide over behind the bandit and if he had sufficient turning room in the horizontal, he'd just turn hard into the bandit then hard turn back to align fuselages for a low deflection shot (and we wouldn't be having this discussion).

Even if the bandit doesn't see the attacker and continues straight ahead, the fighter is going to go racing past the bandit at the very worst, or he will need to honk his nose up and/or suck back his power, which is almost as bad since he is now dangling nose high trying to get his downrange travel under control.

What is more is that the fighter would like to shoot the bandit (after all, he came all this way) but he can't because, being displaced to the side he basically can't cram two level aligning turns into the space behind the bandit...in fact, he really can't quite even cram one. If he could just point his nose at the bandit, he could take a medium to high deflection shot and perform a high yoyo to address his impending in close overshoot.

Incidentally, I'm not suggesting that pointing your nose at the bandit for a spray and pray deflection shot and following it up with a desperate clawing high yoyo is a good idea...ever. I'm just saying that the fighter is in such a energy/geometry situation that even that bad option isn't an option and the fighter is trying to take lemons and make lemonade.

So what the fighter does is basically make his flight path effectively shorter (just like in every closure reducing BFM) by taking that straight line and turning it into a corkscrew. Again, let's stay with the compliant straight bandit for now. The fighter raises his nose, how much depends on how late he decided to do this and there are no style points for doing a big hiyaka that effectively takes his nose off the bandit for extended periods of time. This is true of all these maneuvers (I'll return to this in a second).

Once the fighter's nose is committed up he makes a rolling pull, looking very much like a barrel roll, into the bandit. I know it says "roll away" which is true but confusing as, if the bandit were turning let's say right INTO you and you barrel rolled left INTO him, it would effectively have you rolling AWAY from the bandit's direction of turn (you left, him right)....simple, no? wink

Again, how big a barrel roll depends on how much a barrel roll the fighter needs. And here I'll turn to the second obstacle in understanding this stuff. The illustrations all seem to suggest you need to make a massive barrel roll to perform this maneuver correctly. Watch that video above again. Does that look like a massive maneuver to you? But if you made a ribbon diagram of what the maneuver actually looked like, it would look insignificant and difficult to understand. This is true for EVERY ribbon diagram of BFM and is the source of many an overshoot. So, ten out of ten for drama but about minus nine million for clarity, huh?

But the ribbon clearly shows the bandit in a turn. Well, that's what turns this from Barrel Roll Attack into a Lag Displacement Roll Attack. With the bandit turning into the fighter, all the horizontal turning room problems that the fighter faced before are exacerbated. This makes the displacement roll AWAY from the bandit's direction of turn, a LAG displacement roll as it will put the fighter into a lag turn geometry. Once the fighter is coming around the "downside" of the barrel roll, he will now be in a descending lag turn, which he can then convert to attack the bandit with a conversion to lead pursuit and even a follow on low yoyo, if he made his roll too large.

Consider that the fighter went from a stuffed lead pursuit situation in which he had only the two outcomes: overshooting or parking his nose in the air to a nice lag pursuit turn (ideally on the bandit's blind side) and you can see why the BRA can come in handy.

Now, you asked what if the bandit just extends? In a guns only situation, great idea! And the bigger an airshow that the fighter decides to make his barrel roll, the better an idea it becomes. An old squadron buddy of mine taught me a very valuable lesson...

"If you are fighting defensive BFM, give the bandit MORE of what he wants, THAN he wants."

So, (playing as the other team for the moment), if the other guy is attacking me and he is digging to gain closure, I'm going to squash my turn and give him all the closure he can take. When he takes his nose off trying to gain space, I'm going to extend and gain some speed and turning room...neither of which he wants me to have.

This is why you don't make big maneuvers like they show in the textbooks. As the fighter takes his nose off the bandit, who should the bandit worry about shooting him down? Not the fighter...at least not until the fighter gets his nose back on and gets back in range. If however, the maneuver is made early (assuming this is possible) and small (again...), the fighter is always in the bandit's shorts and he can keep the pressure on.

Switching sides yet again, if the fighter is smart he didn't bullseye his nose when he made his BRA. Therefore, if the bandit extends or reverses his turn or does something else, the fighter needs to also convert his BRA into a something more appropriate, a low yoyo perhaps or a continued roll to match the bandit's new turn in something of a high side two circle flow (which would look like a tail chase in this case). If, however, the bandit has an advantage in top speed or acceleration (assuming a guns only world), it is possible that the bandit will be capable of foiling the fighter's attack or at least turning it into a potentially long tail chase. Remember, if the bandit can achieve enough turning room to meet the fighter head on, the fight is back to neutral.

It's the constant interplay of the bandit's and fighter's decisions that will drive the fight. How you win a fight is to continually make moves that force the bandit to RE-act and not the other way around.

This is much of the drive that occurred in the 70's and 80's to redefine BFM as a series of flows, rather than a series of set piece maneuvers as you can see how it's easy to get caught up in the idea that a maneuver, once started, must be completed. That doesn't mean that a modern pilot might not still perform something like the BRA. It's just that he is trained to recognize that there is no beginning to the maneuver and no end...even once the bandit is shot down as he might have some friends in the area.

I know you are primarily asking about prop sims in this circumstance but the BRA would work in any guns situation. Of course, the high thrust to weight ratios of modern aircraft give both the fighter and the bandit a few more options to play with in the fight.

On the other hand though, the presence of increasingly capable off boresight missiles and targeting makes giving either side too much room a proposition not without its consequences.

Long winded I know. Hope it helped some.

Deacon

#3881395 - 12/21/13 07:43 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Nicely explained, much better than I could.


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#3882156 - 12/23/13 04:49 AM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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I'll add a little to what's already been said.

I'm not familiar with this exact term, but names change all the time so I don't think this is instructive.

I would begin by noting that BFM comprises maneuvers that are designed to deal with two kinds of problems...closure and aspect/fuselage alignment. Closure means changing the speed difference between you and the bandit...controlling overtake or separation. Aspect/fuselage alignment refers to our position relative to the bandit.

In the situation here, I see the word 'lag' as meaning that closure is excessive and lag pursuit is being used to 'slow down' relative to the bandit. 'Displacement' seems to mean that your aspect is excessive, meaning that you are closer to the bandit's 3/9 line than you want.

Therefore you want to reposition to the bandit's six and move closer to a lower aspect angle.

To do this, folks are describing a version of a rolling maneuver that could be called a 'lag roll' or 'barrel roll'. Both terms describe a relatively slow maneuver that reduces overtake, aligns fuselages, and moves you towards the bandit's six o'clock.

I would not refer to this as an attack so much as I would think of it as a maneuver that is intended to improve upon an existing attack position.

If I have misunderstood the geometry, please let me know.

#3883069 - 12/24/13 02:17 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Hey Andy, good to hear from you!

The "Barrel Roll Attack" was still in the old ACM (now BFM) student books when I was a nugget. It's exactly as you described, which I agree isn't really an attack (at least not a good one) but I think they needed to add something after "Barrel Roll" and, since it was something that the offensive fighter would do, "attack" was as good a term as any. wink

More contemporarily (but not really), it is in Shaw's old book: Fighter Combat Tactics and Maneuvering, which I still have an ancient copy of, and which I think is the genesis of a thousand and one online Air Combat guides.

As an aside, we would routinely use the term to describe the entry into a Rolling Scissors from combat spread in the Training Command. We'd start in a tight spread, say 0.6 to 0.8 NM apart, and the attacker would perform a "Barrel Roll Attack" up and over the top of the defender. To get the setup right, the attacker would ideally pass inverted over and behind the bandit 90 degrees off the entry heading.

That made it a crappy attack but a good setup for the roller.

You must have done the same sort of setup...I'm guessing you just didn't name it?

Merry Christmas BTW,

Deacon

#3883128 - 12/24/13 03:41 PM Re: How to perform Lag Displacement Roll Attack? [Re: Laurwin]  
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Originally Posted By: Deacon211
...and the attacker would perform a "Barrel Roll Attack" up and over the top of the defender. To get the setup right, the attacker would ideally pass inverted over and behind the bandit 90 degrees off the entry heading.

That made it a crappy attack but a good setup for the roller.


LOL!! I hope the folks here appreciate the humor in that!! Had that initial move only been an entry into the Barrel Roll, I imagine the next radio call would have been "Where ya goin', Willis?"

Quote:


You must have done the same sort of setup...I'm guessing you just didn't name it?


Yep...a good drill for introducing the idea of maneuvering in the vertical...a beginning move that then could lead into other lessons.

Quote:
Merry Christmas BTW,

Deacon


And the same to you and yours and all the rest of the SimHQ family!!

Andy


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