Problems with the 4-Leaf Clover

This picture could be eye opening.

The full MS word document is on:

www.slovanet.sk/orsia/f.doc

Oh Mr. Keith you have become an agitator.

I don't have the FAI rules handy, but I think they still use the same diagram as AMA. The only discrepancy between the drawing and the description in the rulebook is whether or not the connector between loop 1 and loop 2(and 3 and 4) is "level flight"(presumably at 38 deg) or a straight arc. The difference looks to be only a couple of feet, so I doubt most judges would even notice. On the other hand, you simply can't do loop 2 if you fly level at 38 deg. So change the book so it reads "straight flight" instead of "level flight and the problem goes away.

Phil, the main problem is, that many of us beleive that the "level flight on 45 deg elevation" is "straight flight"

But I think that picture tells much more that just how to fly that straight segment. If one does the 4-L that way he probably gets poor score. I think judge would not welcome bottoms of upper loops under the tops of lower loops and (from judge position) wider upper loops than lower loops (I mean angular width).

With the modern micro technology we have at our disposal, I am considering having a "heads up display" implanted in such a way that it can be activated, with appropriate grid sections, yet not interfere with my normal vision. Will probably take some getting use to, but I am sure it can be done.
Of course, flying the "perfect geometric" pattern will probably look so alien to the judges that my already poor scores would plummet even further.
But then, a GPS system could be programed to do the same thing, and cleverly hidden in the aircraft with minimal weight penalty. Yeah, that's the ticket.
Bill <><

The biggest problem I see in the 4leafclover, even in expert, is starting too low, down around 30 deg. The flyer then makes the first loop a decreasing diameter so it finishes at the right height for the second loop. The next problem is zooming the plane up after loop one and loop three they are afraid of starting a turn towards the ground too low.

The rulebook drawing shows a perfect cloverleaf, from the pilot's perspective. It uses the 45 deg. great circle path, so the plane flys a straight, neutral elevator, path between the loops. Fly it that way and the judges won't even notice that the plane flew "straight" instead of "level" between the loops as they mark down a 36 pt. score.

Hi Phil,
I still think the heads up display or GSP system would be th ebest for me!! LOL!!
I know what the problems are in my clover..... I start near 45* and fly from there. Usually in the low 30s for a score (Advanced) because I work on not overlapping the loops I think, and I get straight lines between the loops without climbing and diving across.
If/when I move to Expert, I know I will have to bring it down a touch and tighten it up s bit.
Now..... got to perfect the plan to raise the funds for the micro technology! LOL!!!
Bill <><

>The biggest problem I see in the 4leafclover, even in
>expert, is starting too low, down around 30 deg. The flyer
>then makes the first loop a decreasing diameter so it
>finishes at the right height for the second loop.

For once I agree with you. A things have developed, everybody is all too aware that the you enter "lower" than 45. So to make sure that this gets taken into account by the judges, the pilots typically enter the maneuver distinctly lower. The fact that it's only ~8 feet between 38 and 45 degrees doesn't matter - you just want to fly it "lower", so you end up entering very low just to emphasize the fact. So you end up with two teeny loops jammed into the ground, and either two giant loops on top, or at least ovals with the long axis "vertical", to keep the width correct.

I think Colonel Trostle's "42" degree change is an attempt to address this. It's close enough to 45 to not be so far as to require exxageration to make it look OK, and instead you can try to execute 4 just slightly smaller loops that actually fit into the space available. Whether it's *really* 41.88, or 42, or 45, is almost beside the point in practice. But it's important that it changed in the right direction in order to break everybody of the bad habit of overdoing the "it starts lower than 45" for emphasis.

> For once I agree with you. A things have developed,
>everybody is all too aware that the you enter "lower" than
>45.

A lot of the top flyers are flying the 4 leaf way under 90 degrees, with the manuever completely out in front of the them. There is no attempt to be at 45 and 90. More like 35 and 70...

> Of course, flying the "perfect geometric" pattern will
> probably look so alien to the judges that my already
> poor scores would plummet even further.

Bill may have been kidding around, but there seems to be a point here. Since the pattern is 'drawn' on the inside of a hemisphere centered, say, at the pilot's elbow, it can only appear 'as drawn' to a pair of eyes located at that point and fixed at the center of the figure being 'drawn'.

Any other vantage point will induce distortion due to differing perspective--the extreme case being trying to judge a 4-leaf clover drawn on a side of the hemisphere perpendicular to the judge's line of sight.

Judges over time develop a perception of what they think must be a correctly flown figure, but what looks right to them and what is technically geometrically correct from the center of the circle are most likely two different things. Makes you wonder if Stunt is judgeable.

I'm reminded of some advice an aerobatic mentor and former world team member once gave me about the problem facing full scale aerobatic competitors. I was going on about what it took to do a round loop or whatever and he told me that the job of the competitor was to know for any given flight what the 5 judges on the line that day liked to see in all the figures in a sequence. Then know which one (in the old days) would tend to get thrown out high or low. Then know how to fly in such a manner that the remaining three would put down the highest marks on the score sheet.

Point was that it did not matter what 'technically correct' figures were flown like--in the abstract sense. All that mattered was undertanding what the judges that day, that contest expected to see and presenting it to them. It took some of the wind out of my sails to contemplate the pragmatism of that point of view. I could fly the exact technically correct figure--a snap roll in one of the new monoplanes that will depart at 10 degrees AOA, for instance--and if the judge did not see what s/he expected to see--enough of a pitch prior to the rotation to convince them that the airplane must have been stalled, say--then I should not be surprised to see my figure downgraded.

The beauty of the sport for me was in the purity of the diagrams in the Aresti manual, but the reality of the sport was in the eyes of those on the judging line. Which reduced the whole escoterically perfect business of scribing the exact path in the sky to the defined standards of the rule book down merely a sophisticated form of airshow flying--trying to specifically please a very small audience.

But what the hell. Despite the loss of objective perfection, the change did not make it any easier, so it was just as much the same sport as before, only now I knew what the real goal was.

Go to a lot of contests, fly a lot of sequences, study the judges scores with the same exhaustive thouroughness that a hitter studies the tendencies of opposing pitchers, compare that with the way you flew each figure and then go out and give the judges something that looks to them like a high scoring flight.

And hope for a little luck along the way, like gentle winds and a nice number in the order of flight.

Thanks, Cy.
Bill <><

Bill,

You'd wind up looking like Geordie LaForge, Star Trek, TNG... Better than implants, anyway... <g>

It’s quite amazing to me that sometimes the point of some of these really good threads can be totally misunderstood. Fortunately, the vast majority of the info on this forum gets past the silly stuff, and becomes very useful. The point of my article on the clover that I sent to Igor, was to show what is possible on the surface of the stunt hemisphere. We are working on fixing some of the bugs in the F2B rules. Whether or not we as fliers, can actually get it right or not, is not the point. The point is that the rules must be correct first, and then we can start working from there. I was not trying to tell everyone that we have to be perfect pilots, although that would be fun! If we did not try to strive for perfection, we would not have PA and RO-Jett engines, no Trivial Pursuit’s etc., etc………

To do the drawing, I took each step in the clover rules, step-by-step, and drew them on my software “stunt-ball.” You can also do this on any physical “stunt-ball.” The pc version is just easier. If you do this carefully, as I have done, then you will arrive at the same conclusions that I have. The rules need fixing! I sent my article to Igor and a few others, and Igor just thought that it would be nice to share it with the stunt community. It is probably better to keep this stuff on the rules change forums. I suggest that anyone that’s interested should read the article on Igor’s site. We are also trying to get the forum going again to discuss, and sort out the maneuver descriptions in the new F2B rules, so it would be nice to see some objective comments.

>It’s quite amazing to me that sometimes the point of some of
>these really good threads can be totally misunderstood.
>Fortunately, the vast majority of the info on this forum
>gets past the silly stuff, and becomes very useful. The
>point of my article on the clover that I sent to Igor, was
>to show what is possible on the surface of the stunt
>hemisphere. We are working on fixing some of the bugs in the
>F2B rules. Whether or not we as fliers, can actually get it
>right or not, is not the point. The point is that the rules
>must be correct first, and then we can start working from
>there. I was not trying to tell everyone that we have to be
>perfect pilots, although that would be fun! If we did not
>try to strive for perfection, we would not have PA and
>RO-Jett engines, no Trivial Pursuit’s etc., etc………
>
>To do the drawing, I took each step in the clover rules,
>step-by-step, and drew them on my software “stunt-ball.” You
>can also do this on any physical “stunt-ball.” The pc
>version is just easier. If you do this carefully, as I have
>done, then you will arrive at the same conclusions that I
>have. The rules need fixing! I sent my article to Igor and a
>few others, and Igor just thought that it would be nice to
>share it with the stunt community. It is probably better to
>keep this stuff on the rules change forums. I suggest that
>anyone that’s interested should read the article on Igor’s
>site. We are also trying to get the forum going again to
>discuss, and sort out the maneuver descriptions in the new
>F2B rules, so it would be nice to see some objective
>comments.

Hi Keith,
I appreciate the efforts you have put forth in drawing/illustrating the 4 leaf clover manuever. It is obvious that there is a need to correct the rules.
Unfortunately, Cy (perhaps others who did not respond) was the only one who saw through my post(s).
Since I am, probably, the author referred to in the "silly stuff" comment, maybe a little insight into my reply is necessary.
Being human, like everyone else here I hope, and of well above intellegence and insight, I all too often see the foibles of our treatises when discussing the subjective judging of an event that is of a different perspective in regards the person in the inside of said hemisphere (pilot) vis a vis the person(s) on the outside (judge), who is at a different angle and distance, from same said hemisphere.
For anyone to truly believe that a manuever can be totally described, at least in writing, to the point that both the pilot and judge are "seeing" the same thing is beyond us all. Re-writing rules will only be of a limited benefit.
But, I surmise, the correct *definition* as to what can actually be performed within the bounds of the limited area we are confined to, is of great value.
However, I stand behind the somewhat veiled implications (too well hidden I suppose) I made as to the *human* factor of judging being the final, determining, factor. A Judge *scores* what he sees and believes to be correct, taking into consideration all of his/her human factors of sight and perception.
I sincerely wish to commend you on the efforts you put forth to clarify these points, and do realise that certain elements the are written in the rules are incorrect. A glaring example is the 5 ft. radius turn which yet to be truly realized.
To simplify: What I see from the handle is different (has to be, and will always be) from what the judge sees. What I have to learn, as Cy so apptly stated, is what the judge sees so that I can present a figure that will will achieve an increasingly higher score.
I hope you see where I am coming from, as a competition flyer, and realize that I am not attempting to belittle your efforts to correct the rules.
Regards
Bill <><

>To simplify: What I see from the handle is different (has to
>be, and will always be) from what the judge sees. What I
>have to learn, as Cy so apptly stated, is what the judge
>sees so that I can present a figure that will will achieve
>an increasingly higher score.

There's dozens of examples a really good competition aerobatic pilot will give you about how you deliberately (if subtly) distort the performance of a figure compared to the CIVA manual definition in order to put the perception in the judges mind that s/he saw a correct figure.

The pilots who can win at the world level know what it takes to induce the perception in the judges mind of a 'perfect' figure. And as much as we all go on about judging impartiality, there are certain trends that come and go in the presentation style that will garner more or less points.

It's part of the competition pilot's job description to know what they are and adjust accordingly.

Hi Bill,
No problem. Thanx for clearing up what you were getting at. I figured it out anyway. I just think that we were getting off the point a bit. These kind of "heavy" rules discussions are better kept in forums like Igor's rule change forum anyway.
I hope to me meet you at the world champs in Muncie, if you are going to be there. All the best.

I had this idea.

If the path of the model was to be, from the pilot's point of view, a straight line and not an arc, wouldn't it be like the green line?

>I had this idea.
>
>If the path of the model was to be, from the pilot's point
>of view, a straight line and not an arc, wouldn't it be like
>the green line?
>

No. That would only look like a straight line if you looked at it from an infinite distance away, or with your sightline in the plane formed by the arc (which is something like 55 feet off the ground, and parallel to the ground).

That is exatly like written in #24, #31, #33. That green line is level which is paralell to straight ground, but "paralele to straight" on ball does not mean "straight".

... and why did't you do that line longer? you will clearly show how it crosses all loops

>I had this idea.
>
>If the path of the model was to be, from the pilot's point
>of view, a straight line and not an arc, wouldn't it be like
>the green line?
>
>Ion

Any straight line from a pilots point of view (well, an eyeball at the center of the hemisphere) would be a great circle route in some direction with the plane defined by the circle cutting through the center of the hemisphere. To actually see a straight line across the inside of the hemisphere, the pilot would have to extent the arm straight out from the sholder, hold the handle in his eyeline to he airplane and then keep it there so that the airplane was flying about a point between the pilot's eyes--at which point I'm willing do dismiss parallax.

Anything else including a green 'longitude line' such as Ion has drawn will be more or less a looping figure. To see this just keep raising the altitude of the airplane until you are scribing a 'level line" near the top of the circle. That is really a loop done overhead.

The green line is level relative to the planet, not the pilot.

The only case where the two coincide is where the plane flies level at eyeball height. Then it's path is 'straight' from the pilot's point of view and 'level' from the planet's point of view.

Make sense?

Keith, can you add to the first picture also 41.88 deg level line together with 38 deg level line? I think it will better show proper approach to the 4L.

>Keith, can you add to the first picture also 41.88 deg level
>line together with 38 deg level line? I think it will better
>show proper approach to the 4L.

No problem, Igor. In the picture you can see the approach problem, because the rules ask for the first loop to be a complete 360 degree loop, so I would say that this means that it ends where it starts. You can also see why I said that maybe a better place to enter is at 38 degrees, or you could fly through it as Brett said, and start at 42 degrees where the tangent point is. This is something that we need to clear up on the F2B rules change forum.

The 45 degree great circle path is the only horizontal path (upright and inverted) that can connect loops 1 & 2 and 3 & 4, so that it satisfies the rule requirements. Flying this path as level flight parallel to the ground, makes it impossible for the loops to be tangent to another 2 loops. It also makes the requirement for the distance of the level flight from loop 1 to the start of loop 2, to be equal to the diameter of loop 1.

The loops have to be approx. 42 degrees arc size (41.88) as Pete Soule calculated, but if you look at the drawing, you will see that the entry point is back at 38 degrees. Does it look different when you fly the horizontal lines as great circle paths? You bet! Flying parallel to the ground looks like a downward curve, and flying the "Straight line" or great circle path, makes it look like an upward curve. Have a read of the artcle on Igor's site, and I've addes a few more drawings to explain a bit more. Enjoy!

Keith

Keith,

Thanks a lot for the explanation. A straight line at higher elevations on a hemisphere will appear as a slight arch extending toward the top elevation of the hemisphere! Hmmm = straight tops of squares! Of course they are so short as to make the arc relatively
un-noticable.

Yes, it is good idea to read the orriginal text with pictures. If the .DOC format is problem I can convert it, just tell me.

but to the point - I want add that the tanget line at intersection of loop 1 and 4 and also loop 2 and 3 is identical line and it is that 45 degree great circle path. By other words, both - the 42 deg level line as well as 38 deg level line are crossing proprerly fitted circles. The only line which is not crossing those circles (loops) is that 45 degree great circle path. It means that the model at the intersection should not fly any level direction (heading paralel to the ground) it should fly at that 45 degree great circle path.

"unless begun at an elevation of 41.88 degrees as you have shown."

Need a rather steady hand and good geometrical judgement to achieve that one.

>Yes, it is good idea to read the orriginal text with
>pictures. If the .DOC format is problem I can convert it,
>just tell me.
>
>but to the point - I want add that the tanget line at
>intersection of loop 1 and 4 and also loop 2 and 3 is
>identical line and it is that 45 degree great circle path.
>By other words, both - the 42 deg level line as well as 38
>deg level line are crossing proprerly fitted circles. The
>only line which is not crossing those circles (loops) is
>that 45 degree great circle path. It means that the model at
>the intersection should not fly any level direction (heading
>paralel to the ground) it should fly at that 45 degree great
>circle path.

Or in other words, a straight line from one tangent to the other, in the pilot's frame of reference. That's the whole idea.

Brett, I did not want to use that "straight line". It is very often misinterpreted - I very often hear that "parallel to ground" = "straight".

>Brett, I did not want to use that "straight line". It is
>very often misinterpreted - I very often hear that "parallel
>to ground" = "straight".

Well, that isn't what it's supposed to be. It's supposed to be a "square loop" from the pilot's perspective. In fact, one or other of the judges guides says precisely that. The only way that happens is if the maneuver sides and tops are "great circle" tracks of equal angular length. It's projection in to latitude and longitude is whatever it comes out to be. It's identical to what would happen if you took a plane perpendicular to the axis of symmetry, and drew planar figures on it.

I thought that we had resolved this latitude/longitude question long ago - like in the 70's. But apparently not.

BTW - the 4- leaf entry point is at the tangent point of the 1st and 4th loop, which *is* at 41.88 degrees - not at the lowest "latitude" point of the first loop.

You are right, the “straight line” is well defined in actual draft as “closest distance”. It is the same as arc of the great circle. And rules also carefully distinct between “straight” and “level”. For example the vertical segments of squares are defined as “straight”, while tops of squares are “level at 45” – means they should not be “straight” by upper definition. The same is in 4L definition. The horizontal segment is defined as “level at 42 deg” – means not straight – and now try to ask someone if that horizontal segment in 4L should be straight or not I never got answer “NO” which is by this definition proper.

You wrote: >>>entry point is at the tangent point of the 1st and 4th loop, which *is* at 41.88 degrees<<<

YES - formally! And that is the problem. If that horizontal segment is defined as “level” then the entry point defined as “entry to the first loop” is:

either at 38 degrees and thus at its lowest point thus before the intersection at 42 degrees;

either the level is at 42 degrees and the approach is not tangent, it is intersecting first loop thus the entry must be some corner instead of tangent.

sorry, I mean poor = low ...

BTW ... we have only 5 mil people in Slovakia, so our language is not usefull for any international contact and my only experience in English (beside C/L forum or newsletters) is with German speaking people, so excuse me if I do mistakes, or better - tell me, could be I will get better

Hey Dave,
Now we're getting somewhere! Virtual reality in stunt! I like your idea. Coupled with the implanted heads up display I could fly the perfect patter, and get scored about a 290. (did get that from one NATS judge one time...... he was only 184 points lower than one of the others, talk about spread).
Great idea!
Oh yeah, got to build another Argus. Last one is history thanks to a flame out going vertical.
Bill <><

Brett, I think Keith go little further with his step-by-step test. He points the entry point to the figure - especially disproportion between 42 deg elevation where loops touch each other and lowest point of the first loop which seems to be at 38 deg elevation - and that is that smooth tangent entry point. So it looks the old description asking for 38 deg level flight before 4L was proper, does not matter that intersections are at 42 degrees.

There is also another idea - the entering the 4L by that 45 deg main circle path – that really looks like the proper entering. Question is, if it is practical. It could be little problematic to enter 45 deg elevation down the strong wind. In any case a judge should NOT take care how the model comes to the 4L as it starts at begin of first loop.

>Bill you certainly cannot fly 5ft corner, because model is
>not able do it, but judge can see what you did and what you
>had to do. But it is different if you cannot do figure
>because its definition is internally incosistent, then the
>result depends on interpretation.

I think the point I was trying to make is that, regardless of how you fiddle with the rules or the laws of physics and aerodynamics, the results you get on the score sheet are always a matter of interpretation--by the judges you are flying for.

If the rules will hold still, then all you gotta do is fly and fly and fly in front of enough judges until you know what it takes to make them write down high scores.

If you change the rules, then they gotta think (some of them, anyway) about maybe changing what kinds of scores they write down for a given performance of a figure.

Seems to me you may as well leave the rules alone and put more gas through the venturi in front of judges and study the results.

Just a thought.

Keith, I do not see that first picture, but the second is I think not proper. I would say that the upper loop (with that text “bigger top loop”) has proper size while that lower is too small. Or do I see it wrong?

Igor, What I am showing here is that the rules says that we must enter at 38 degrees, fly loop 1 so that it touches first the vertical line directly in front of you, then continue going round until the path is tangent to the "wingover path" at 90 degrees to you. This will automatically set the size for loop 1. You then complete the full 360 degree loop back to where you started. Step 2: Fly along straight and level flight at 38 degrees and perform 3/4 of an outside loop for loop 2. Now........the only space left for loop 2, is an arc of 38 degrees, and that is why the bottom loops are too small.
What I did not show in my drawing, is that the rules state that the straight and level flight to loop 2, should be equal to the distance of the diameter of the first loop. This would bring loop 2 closer to loop 1, and it would not then be at a tangent to the vertical line. Would you like me to do a drawing to show this? This will be no problem.

aaaa.... now I understand, that "bigger" upper loop is bigger than that lower, but not bigger than it have to be yes?

It means that upper loop has proper size, while that lower is too small. Yes?

>aaaa.... now I understand, that "bigger" upper loop is
>bigger than that lower, but not bigger than it have to be
>yes?
>
>It means that upper loop has proper size, while that lower
>is too small. Yes?

We broke the code. The four leaf clover is impossible to fly as described by the AMA and FAI rulebooks. These rulebooks now require the entry to be at 38-degrees, all loops to be tangent with each other with the bottom two loops tangent to the equator line (horizotal flight altitude) and the top two loop tangent with the vertical plane through the center of the circle and all loops are to be the same size. This cannot be done with the 38 degree entry point and 38 degree elevation angle for the center of the maneuver. With the 38 degree elevation angle, the loops cannot be the same size if the top loops are to be tangent to that vertical plane through the center of the circle.

This I do not understand well:

>>>These rulebooks now require the entry to be at 38-degrees<<<
This is OK I think. The lowest point of upper loop is at 38 deg, and 38 deg level flight would be tangent yes?

>>>all loops to be tangent with each other<<<
This is OK if loops are of diameter 42 degrees yes?

>>> with the bottom two loops tangent to the equator line (horizotal flight altitude)<<<
No problem at all.

>>>the top two loop tangent with the vertical plane through the center of the circle and all loops are to be the same size<<<
This is also OK.

So that is why do not understand this:
>>>This cannot be done with the 38 degree entry point and 38 degree elevation angle for the center of the maneuver.<<<
Yes, but we do not start this figure at center of maneuver, we start lowest point of the first loop. And that is at 38 deg. And if you then continue from tangent point of upper and lower loop by the great circle path, then you will come to the center of figure which is at 45 deg elevation.

You can see on last picture in message #51 that there are several different important numbers:

38 deg – lowest point of upper loop
??? deg – tangent point
42 deg – highest point of lower loop
45 deg – center of figure

>> I came to the diametric opposite conclusion - this
>>description is *precisely* what was intended. Take a vector
>>from the "origin" (i.e. pilot) to the intersection of the 45
>>degree "great circle". Then draw in a plane perpendicular to
>>this vector. The pilot sees a projection onto to this plane.
>>You then draw 4 equal circles with radii of 20.94 degrees
>>into the 4 quadrants. Viola, perfect 4-leaf clover. And it
>>will look like 4 round loops to the pilot, and connected by
>>straight lines, and symmetrical.
>>
>Brett, I'm not quite sure what you mean here about "this
>>description is *precisely* what was intended." What you describe is exactly what I've drawn in the picture from Igor. The description that I was referring to is the one in the present (not the new rules)F2B rules, which are the same basically as the AMA rules. The horizontal lines are defined as being straight and level flight. This means parallel to the ground and not a "straight line" which is as you know, a great circle path.

No. The only way a square looks square is to fly the tops as a great circle.

>BTW, the squares in the present rules have tops that are
>defined as level flight at 45 degree line elevation. The
>bottom and sides are indeed great circle paths. If the top
>was a great circle path, and of equal length to the bottom
>and sides, then the apex would be higher than 45 degrees.
>
>The main point is that what Igor and I are saying is that
>the rules should be correct, maybe even a little vague, but
>they should not be wrong, and as far as the clover goes, the
>present rules are WRONG!
>

No. I think you are assuming that, for example, the level 45 degree flight is at a constant altitude above the ground, and I say that its supposed to be a straight line to the pilot (i.e. great circle to outside observers). Keith's change to the 4-leaf description is precisely consistent (to 4 significant figures (!)) with this interpretation.

Thought experiment for you. Instead of performing the 4-leaf with the "cross" at 45 degrees, consider it at 90 degrees, i.e. axis of symmetry directly overhead. No debate about what the connecting paths are, perfectly clear that all 4 loops are the same size. Take the same manevuer and rotate it so the axis of symmetry is at 45. That's what it's supposed to be like.

Brett, We have got to the point of why Ted Fancher does not normally get into these forum discussions. As he said before: "I sort of avoid these issues except in face to face discussions when your fingers don't get worn out from the bazillion exchanges necessary to get a clear case made for a given point of view."

We seem to be saying the same thing different ways. I also have Pete Soule's paper on the clover. The 42 degree loops are correct, the great circle path is correct. What I'm saying is that the description in all the rules where it states that the horizontal joining line is flown as straight and level, and parallel to the ground is wrong i.e the rules are wrong. I know exactly how it can be done, I can draw the diagram from any view, and show what is possible and what is not. All I'm saying is that the rule description is wrong. Please have a look at the new F2B rules (March 04 on Igor's site), and try and follow each step carefully, and then stick it on the hemisphere.

These same rules also describe describe squares with sides that are vertical to the pilot (perpendicular to the ground), and the tops flown parallel to the ground. This makes the top considerably shorter than the bottom. The old F2B rules, that we will be judged to in this coming world champs in Muncie, describe square loops with equal length sides and tops that are flown at 45 degree line elevation angle. Does this not mean parallel to the ground? I continually hear opinions about how to perform squares that look square to the judges. The rules however, do not actually ask for this. The F2B Judges Guide just before the Peter Germann version, states quite clearly in point 4.2.16.7 "If flown as per the book, the judge being placed exactly upwind shall expect to see a square shaped manoeuvre with slightly outward slanted verticals." We do we then try and make them look square?? A square can indeed be done that looks square, but only to one judge. I actually don't mind if the rules ask for squares with wiggles in the sides, just as long as the rules describe it properly. If the rules are vague, is this not what is causing all the many different opinions of the same story??

This is basically like your point when you took Dave Cook to task in Stunt News over the point of the first level laps setting the height for the bottoms of all the maneuvers. It could be a great idea. Dave Cook has some very valid points, but the bottom line is.........it is not in the rules! I come back to my reason for doing all this in the first place. We need to make sure that the rules are at least technically correct. Sure we can never fly perfect patterns, sure the judges can't see many of these finer points easily, etc. etc......but to get a better universal, common understanding of the rules, we need to fix the basic things that are wrong first, and work from there.

I would really appreciate your help on the rule change forum. I will try to get a good discussion going again with Igor's help. Thanx.

Brett............that is exactly what my drawing shows if you rotate it overhead as it is. Now I ask you with tears in my navy blue eyes (they're actually royal blue!)Why did it take us all so long to figure this out from the first drawing in Igor's posting?? Just for fun, I've rotated it and posted it below. Enjoy!

Darn it!

I had thought of the same thing some time ago, but I completely forgot about it.

Why did it take me so long?
Because I'm a dummy!

Ion:'(

>>>Thought experiment for you. Instead of performing the 4-leaf
>>with the "cross" at 45 degrees, consider it at 90 degrees,
>>i.e. axis of symmetry directly overhead. No debate about
>>what the connecting paths are, perfectly clear that all 4
>>loops are the same size. Take the same manevuer and rotate
>>it so the axis of symmetry is at 45. That's what it's
>>supposed to be like.
>>
>> Brett............that is exactly what my drawing shows if you rotate it overhead as it is. Now I ask you with tears in my navy blue eyes (they're actually royal blue!)Why did it take us all so long to figure this out from the first drawing in Igor's posting?? Just for fun, I've rotated it and posted it below. Enjoy!

I was going to try to stay out of this, but I thought something more needs to be said about this one.

First, I think Keith Renecle's graphics for illustrating various parts of our pattern are the best I have seen. He has devised a tool that will be very useful for even a casual student of how the maneuvers should actually appear on the surface of the hemisphere where we operate our airplanes. Keith has generated these graphics for the various manuevers and is the best thing that has happened since Rich Porter's Stunt Ball and Charles Mackey's article in Model Airplane News years ago in forming wire figures on a hemisphere (actually a bowling ball)to show the shapes of these maneuvers.

Also, I think Keith Renecle has shown the validity of Pete Soule's calculations that the loops of the four leaf clover must be "approximately" 42-degreees in diameter in order to fit the requirements of the rulebook where the four loops are tangent to each other, the bottom two loops are tangent to the "nominal" five foot altitude and the top two loops are tangent to the vertical plane that passes through the center of the circle. Also, the diagram that Pete Soule has in his paper to determine the proper diameter of these loops hints at the same thing that Keith's graphics clearly show that the mid elevation tangent points of each of the left and right pairs of loops is not defined by a constant (approximately) 42-degree elevation angle. I am not sure if Keith was able calculate mathmatically that these tangent points are defined by that great circle path that is 45-degrees from the horizontal as shown in his graphic of if he found a path that appears to be tangent to those points and it appears to be 45-degrees. Neverthless, it is not the constant elevation angle that is currently defined in the FAI and the AMA rules (which is the "approximate 38-degree elevation." Now, the AMA rules are gong to be changed, starting in 2005, that this intersection is to be "approximagely 42-degrees". The 42-degree loops are technically more correct than the current rulebooks (FAI and AMA) in that the loops can be flown the same size and can meet the tangency requirements of the rulebook. (These tangency requirements cannot even come close to being met with the current 38-degree loops if the loops are the same size which is also specified by the rulebook.) At least, it should be easier for a pilot to more properly fly and a judge to better evaluate the size of the loops while meeing the tangency requirements of the rulebook rather than the often times seen distortion where the loops are flown as small as 38-degrees (or less) with the tops of the four leaf clover well in front of the pilot rather than being above his sholders at those tangent points to the vertical plane through the center of the circle. Unfortunately, it would be difficult for the pilot to accurately fly that 45-degree great circle path between the tangent points of the left and right pairs of loops. It will be even more difficult for a judge to see this with any great amount of accuracy. After all, the judge is looking for the tangency point of the first and fourth loops - that tangent point does not appear as a physical colored marker hanging up there in the air - the airplane has flown two more loops before it gets back to that spot. Granted, the second and third loops are flown consecutively and it is a bit easier to "see" their tangency, but it will still be difficult for a judge to determine if that tangency is close to that 45-degree great circle path or even if the tangent point is across the constant 38-degree (soon to be 42-degree elevation) angle. I will maintain that even the most experienced and conscientious judges cannot do this well even if located at the best possible position outside the circle (or even if the judge could be immediately behind the pilot, these nuances in intersection angles could barely be detected.) There are many more problems in flying a decent looking four leaf clover than just these tangency angles. Please do not misunderstand my intent. I think that Keith Renecle's graphics are supurb and offer a better understanding of this manuever. But I do not think that a complete wholesale revision on how the maneuver is to be flown or judged is warranted by the revelations of these graphics and how those middle tangent points are positioned. It is not possible to fly the four leaf clover as described in the current rule book. The new "approximate" 42-degree elevation angle and loop diameters will make it possible to more accurately meet the tangency requirements of how the maneuver is described. (The constant elevation angle to define the middle intersection tangency points still makes the four leaf clover impossible to fly as described, but not to the extreme of the current rules. There will be very few judges that could ever tell the difference if the four leaf clover is flown precisely as Keith's graphic shows or one where the horizontal intersections are defined by a constant 42-degree elevation. I say this because I have the records over the years of good, experienced, concientious judges who give good scores to four leaf clovers that are entirely too small, even with the 38-degree standard.

Now, to respond to Brett's "thought experiment" to place the axis of symmetry directly overhead. I think Brett and Keith Renecle are saying and showing the same thing with this location of the manuever with the center directly over the pilot's head. It would be possible to position that maneuver anywhere on the hemisphere and there would still be the four equal size loops and the relative tangent points of all of the loops are always the same. The tangency paths of the intersections are all and always great circle paths regardless of where or how this maneuver is positioned on the hemisphere. It is easy to see those great circle paths when its center is at the top of the circle because those tangency paths are all longitudes that pass through the top of the circle. The size of the loops that we fly in the PA pattern are fixed because of the tangency requirements defined by the rulebook.

This thread brings up another subject that should probably be better discussed in another thread. But it is interesting to consider the difference between constant elevation angle altitudes used to describe certain portions of the PA pattern and great circle paths.

The attitude of our models flying on our hemisphere with the wingtip tethered to the center of the hemisphere is significatly different than an untethered aircraft flying over the surface of the earth. A full scale aircraft flying a great circle path does not change directions left or right even though the compass heading may change significantly during that flight. Now, our tethered models can easily fly great circle paths like on wing overs and horizontal flight at the equator of our hemisphere with essentially not elevator input (assuming a stable flying model). But if a great circle path as shown in Keith Renecle's graphic that starts on one side of the circle with a climb of 45-degrees and ends up on the other side of the circle in a dive at 45-degrees, constant elevator adjustment must be made to follow this path. In contrast, if a constant 60-degree elevation angle is maintained (where the model remains at a constant altitude for an entire lap, the model has essentially flown a loop but with no change in elevator input to maintin this level flight (again assuming a stable flying model). I think what I am trying to say is that except for wingovers which follow a lattitude line across the top of the circle and horizontal flight at the equator of our circle, great circle paths are difficult to fly with our tethered models. Great circle paths appear in various portions of our pattern other than the wingover and level flight, like the vertical sides of the square loops and square eights and the legs of the triangles and hourglass. Interesting things to ponder.