Intercepting the Big-way I

[remko 0]

It's a bit technical, but give it a try. Latest version can be found here:
http://bigrock.com/~remko/crew/Intercepting_the_Big-way_I.html or
http://cluebox.org/~remko/crew/Intercepting_the_Big-way_I.html

Enjoy


Intercepting the Big-way part I

Introduction

This is supposed to become a small series of articles about CReW. Most CReW articles deal with what to fly and how to fly. These writings will be about where to fly and why, in relation to a big big-way. Mostly, it will be the glue around some pictures I will draw. These drawings are really the most important part, and I intend to introduce some new terminology along with them, so we know what we talk about, when we don't have pictures around to clarify.

This stuff comes from my background as a fighter pilot, but it is applicable to any being wishing to join a moving object and continue the journey together. Being it two cars crashing at a junction, or a puma catching a rabbit in the desert. Our objective will be not to crash though, and not to get eaten in the process.

Keep in mind that all this is related to the last part of a large big-way jump. From getting out of the aircraft far ahead of the formation, up to arriving near the formation in echelon.

I was inspired by Rusty Vest, who kept bugging me to reproduce the chalkboard scribbles I put up during a briefing for the 2005 Canopy Formation World Record in Lake Wales. And much inspired by Chris Gay's enthusiasm during that and other events.

OK, here we go, the fundamentals of interception...

The cross roads (Have a look at the picture)

In this first picture we see two cars A and B approaching a junction. We assume they both drive with the same speed. If both cars keep on going, this otherwise uneventful situation will result in a collision at point C. Intercepting is all about angles, and there are more of those than you think. Lets have a closer look. The first one we all know.
Heading (H)

Car A is driving towards the North Pole. His heading is 360 degrees. Car B is going to the West coast. His heading is 270 degrees. Heading says something about where we end up if we keep on going that direction. The next paragraph explains how the heading of car A and B relate.

Heading Crossing Angle (HCA)

The difference between the two headings is called Heading Crossing Angle. It is the angle between the two headings. In the picture it is 360 - 270 = 90 degrees and marked as HCA.

Heading Crossing Angle says something about the severity of the collision. Imagine car B coming from the North and driving on the left side of the road heading South. The HCA would be 180 degrees (360 - 180) and the collision most severe. If car B would drive along side car A, also heading North, the HCA would be 0 and there is no collision at all.

In other words, on two objects traveling at the same speed, HCA determines the closure, the speed at which two objects close in on each other. It is an important tool in the final stage of the intercept. It determines if you crash or shake hands.

Antenna Training Angle (ATA)

`Antenna Training Angle' is a difficult name used for the simple fact that we want to point out our target to someone else. Imagine that car B is a police car with two officers in it, on the road to write speeding tickets, and the driver wants to tell his buddy to point his ray-gun at car A. He would say: `Your target is 45 degrees to the left!' So the Antenna Training Angle is the angle between your heading and the direction the antenna of the ray-gun is pointing. In the picture it is 45 degrees left and marked as ATA. Notice that the ATA can never be more than 180 degrees and has a direction associated with it (left or right). As a side note, ATA can also be expressed in clock codes, 12 o'clock being 0 ATA also called `On the nose', 1 o'clock equals 30R, 7 o'clock is 150L and so on.

Antenna Training Angle says something about the position of the target in relation to yourself. But it can give us more information than just that if we look at how ATA changes over time. Again, look at the picture while you read.

Imagine that you are in car B. Suppose car A is a little closer to the junction. Lets say the ATA is 30 degrees to the left (30L). We know from experience that car A will pass in front of us. Now try to picture what happens with the ATA while car A drives past our nose. ATA becomes smaller and smaller until car A it is exactly in front of us (picture yourself pointing that ray-gun). We would say: `He is on my nose.' (ATA=0). It is important to realize that there will be no collision!

Now imagine that car A starts further away from the junction, say 60L. This time car A will pass behind us. To fully grasp the essence of ATA, it is important that you play this as a little movie in your head, while you concentrate on the ATA. It will become bigger and bigger. When we cross the junction in front of car A it is in our 9 o'clock position, ATA is 90L. It moves toward 150L and when car A finally crosses the junction exactly behind us ATA is at it's biggest, 180. Again, no collision.

So, what happens when ATA remains the same?... BOOM! The nice thing about ATA is, when we fly aloft, not bound by roads, we can easily change it by turning. When we turn towards our target, ATA decreases and we will pass behind. This is also called lagging. When we turn away from the target ATA increases and we will pass in front. This is also called leading. When we steer to keep the ATA the same, ultimately resulting in a collision it is called steering CATA (Collision Antenna Training Angle). It is the fastest way to join a formation from a given position (not necessarily the safest way).

Aspect Angle (AA)

The opposite to ATA is Aspect Angle. It is not the position of the target in relation to yourself, it is your position in relation to the target! Aspect Angle is historically referenced to the tail of the target, because that's where fighters, and basically any predator, wants to end up, behind the target. So, the Aspect Angle is the angle between where the targets tail is pointing and the side you are facing. In the picture it is 135 degrees right (135R) and marked as AA. If you find it easier, you can remember it as `Ass Angle'.

Anything I have written about ATA applies in a similar way to AA, except the reference is now the target and not yourself. This leads to one big difference though, you can not easily change the AA. If you are far away from the target you will have to fly a long way to change the AA by a few degrees,and it is easily negated by the target with a small turn.

Aspect Angle says something about how fast you can get to your target. If the AA is 180, you can meet it head on and be there in a heart beat. if the AA is 0, you could be trailing it forever...

The Aspect Angle is the most important parameter of an intercept but also the hardest one to control. Heading Crossing Angle and Antenna Training Angle are the tools to work on the Aspect Angle.

Conclusion

We had look at the different angles of an intercept. Next time we will see how they can be useful in catching that big big-way.

--
Everything you know is wrong. But some of it is a useful first approximation.

[leapdog 0]

This is interesting. I see how it relates to fighter pilots and how predators in the wild are studied. I see how it is usfull for CRW dogs. I have been using the concept but just didn't know how to explain it such terms. What I have been doing is to have a new CRW dog walk a run back in small scale with me on the ground.

I have a question. Is the writting meant for an experienced CRW dog or New CRW flyers? Perhaps both?

Gunnery Sergeant of Marines
"I would like it if I were challenged mentally at my job and not feel like I'm mentally challenged." - Co-worker

[remko 0]

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What I have been doing is to have a new CRW dog walk a run back in small scale with me on the ground.

That is exactly how I show newbees how to get to a formation, but normally I don't get into detail, just tell them where to go and what to look for.

This article, and one or two more to follow, are meant to explain exactly what we are looking for and why, while we intercept a formation.

Quote

I have a question. Is the writting meant for an experienced CRW dog or New CRW flyers? Perhaps both?

I hope both. I know it hasn't been discussed much, and not in this way. And although it becomes more important when the formation grows, It can be practiced one on one too and is a lot of fun to do.

I plan on applying the new terminology in some practical examples in the next article, to further explain their relationship. It can be used to explain a student how to set up a pin-base, but my goal will be to work towards clarification of the flow of the 100-way next november.

--
Everything you know is wrong. But some of it is a useful first approximation.

[leapdog 0]

Quote

This article, and one or two more to follow, are meant to explain exactly what we are looking for and why, while we intercept a formation.

While I think what you are writing is important and is a good basis for a text explanation, I'm not sure that everyone does what you are writing. Or maybe better put, consciously thinks that way.

Quote

I have a question. Is the writting meant for an experienced CRW dog or New CRW flyers? Perhaps both?

I hope both. I know it hasn't been discussed much, and not in this way. And although it becomes more important when the formation grows, It can be practiced one on one too and is a lot of fun to do.

I plan on applying the new terminology in some practical examples in the next article, to further explain their relationship. It can be used to explain a student how to set up a pin-base, but my goal will be to work towards clarification of the flow of the 100-way next november.

[remko 0]

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I enjoy the technical aspect of what is written thus far.

That is my strong side, but also my week side. I'm aware of that.

--
Everything you know is wrong. But some of it is a useful first approximation.