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Aresti Made Simple

RV8Squaz

Well Known Member
For those that may have an interest in aerobatic competition, I realize that one of the things that may seem complicated is the Aresti System. The Aresti System is a system of depicting and scoring the many aerobatic figures and their multitude of variations. It?s called a system because there is method to the madness. It was designed by a Spanish Air Force Colonel, Jos? Luis Aresti, many decades ago and it is used universally for aerobatic competitions. The files below are written for the r/c (radio-controlled aircraft) community and it is presented in a simplified method. Caution, there may be some differences from the actual Aresti catalog.

http://anti-gravite.com/fichiers/IMAC/Aresti Made Simple.pdf

http://www.nzrcaa.co.nz/wp-content/uploads/2015/06/Aresti-Dictionary.pdf


This is the Primary Known sequence for 2017 and 2018:

https://www.iac.org/system/files/Primary 2017.pdf

It?s a:

1. 45 degree up line
2. A one and a half turn spin
3. Half of a Cuban 8
4. A loop
5. A 180 degree turn
6. Am aileron roll or technically a slow roll.

If you?re already doing some aerobatics, this could be something to shoot for. If you haven?t already please get some aerobatic training before trying this at home.

I hope this inspires someone to give it a go and enjoy this sport as much as I have.
 
Thanks for posting this Jerry! Good luck to you as you get started with the contest season. I'm getting ready for Borrego Springs, CA in April, then it'll be one a month for the rest of the year!
 
You're welcome Gash. Wow! A contest every month! That's pretty aggressive, but that's how you get good too.

I'm getting ready for our first contest at the beginning of April, The Snowbird Classic in Dunnellon FL. I did four last year. I'm hoping for 5 or 6 this year. I say hoping because we have a lot of travel plans. Many of the contests are over the summer and I'm hardly home over the summer due to work and family vacations. It's a good problem to have!

Good luck to you too!
 
Flying the sequence - Figure #1

Primary Known 2018

Getting from an Aresti drawing of a figure to actually flying the figure perfectly is what IAC competition is all about. What may seem like a true representation of the figure from the cockpit may differ greatly from what the judges see from their vantage point on the ground. Coaching from the judges' vantage point is essential to success in competition. So let's take it one figure at a time.

But before you fly figure #1 you must enter the box. You will be holding outside the box, listening for the Chief Judge to call you: "Joe Blow, you are cleared into the box. Have a good flight." You are on a base leg at 3500' AGL and do a half roll to inverted to check the security of your seat belt(s) then roll upright, turning 90-degrees as you dive into the box. A 30-45 degree dive into the box allows you to see the box markers easily, orienting yourself in the box for your first figure and picking up speed. Three quick 45-degree wing dips to the judges signals that you are ready to commence your sequence. You level off briefly before starting figure #1. (Note: all figures start and end with a horizontal, level line.)

Figure #1 is a 45-degree up line. Each figure starts with a score of 10 and is reduced by each judge as he finds errors in your figure. Seems simple enough! The pull to the 45-degree line is a constant radius 1/8 loop which is downgraded by one point for every change in radius. The 45 degree line is not wind corrected and is graded on the path of the aircraft center of gravity.
Think of the airplane condensed into a single dot and watch the path this dot takes through the sky. This is the flight path, or track, of the aircraft?s center of gravity. Judging the flight path consists of comparing the observed path with fixed references such as the horizon or the X and Y axes of the Aerobatic Box. Aircraft attitude does not determine the 45-degree line. Actually, if the aircraft slows as it climbs the attitude will appear to increase in order to maintain the 45-degree flight path. Since the 45-degree up line is not wind corrected it will appear steep in a headwind and shallow in a tailwind. Judges recognize the wind effect and mentally disregard it when determining whether the line is a true 45 degrees. However, most experienced competition pilots will purposely fly a 45-degree up line slightly shallow into the wind and slightly steep downwind. Deviation from 45 degrees is penalized one point for every five degrees steep or shallow. The return to level flight is a pushed 1/8 loop which need not have the same radius as the pull to the 45-degree line but it must have a consistent radius to avoid penalty. The figure is complete when the aircraft returns to level flight. Deviation from level flight are penalized by one point for every five degrees off level and/or off heading.

Take a deep breath and ready yourself for figure #2.
 
Ron, little clarification - 45 lines are graded on attitude rather than flight path. Only level lines are graded on flight path.

And the only airplanes that really appear on a 45 attitude when pitched 45 degrees from the vertical zero lift axis are those with zero incidence, symmetrical airfoils, and long thin fuselages. Technical "IAC" 45 uplines in RVs and Citabrias will appear well shallow, and pilots are definitely advised to steepen those up for the same reason Ron mentions adjusting for wind - to make it look good to those half blind judges a half mile away. :) There's more to the story than putting your sighting device edge on the horizon. ;)

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Thanks for the info

Thanks for the info and please keep it coming.

I plan to use this info to give a grade to my neighbors when they are practicing. I have a nice view from my deck in the back of the house.
 
Flying the sequence - Figure #2

Primary Known 2018

Welcome back. It doesn't take long to get from figure #1 to figure #2, so here you are after a very short breather.

Figure #2 is a one and a half turn spin. The 45-degree up line of figure #1 is a perfect setup for the spin as you are at the top of the box (about 3500 AGL) and slowed to near stall speed. The spin must start from level flight so you reduce power to idle and keep increasing pitch to maintain level flight. A five degree descent will get you a one point penalty!

When the aircraft stalls, the aircraft must simultaneously move around all three flight axes:
(1) the nose will pitch toward the ground; (2) the nose will yaw; and (3), a wing tip will drop. Failure to achieve simultaneous motion about all three axes should be considered a ?forced entry? and downgraded one point per five degrees of deviation on each axis. For example, if 10 degrees of pitch and 10 degrees of roll are observed before any motion about the yaw axis is seen, a four point deduction would be made. Note that you can spin either right or left, your choice. (It would be good to practice spins in both directions as you will need to go both ways when you get into other sequences. Imagine a 3/4 spin that you need to exit going to the left of the entry heading.) I goes without saying that over or under rotation of the spin by 10 degrees is a two point penalty. (I did say it, didn't I?)

If the aircraft never stalls, it is apparent that it cannot spin, and a hard zero (HZ) must be given. (Consider a hard zero to be just as bad as a plain old zero for now.) After completion of the one and a half turns, the aircraft must stop rotating precisely on the X axis and in the direction of flight appropriate to the sequence being flown. (To the left or downwind in the illustrated sequence.) Be alert for early stopping of the autorotation followed by ?aileroning? to the required heading. In this case, a deduction of one point for every five degrees of "aileroning" must be applied. For example, in a one-turn spin the autorotation is observed to stop after 345 degrees of rotation and the ailerons are used to complete the remaining 15 degrees of rotation. The highest mark this spin could receive is a 7.0.

Following completion of the one and a half turn rotation, a vertical down line must be seen. It is acceptable for the pilot to achieve this in either of two ways: Immediately after rotation stops, the nose is pitched to the vertical down line and the wings are simultaneously brought to the level attitude; or, the vertical down line and wings-level attitude are achieved as the pilot halts the rotation, such that the prescribed number of turns, vertical down line, and wings-level attitude are all achieved simultaneously. The vertical down line may be as long as desired but must be a true vertical line or a penalty of one point for five degrees off vertical will be assessed. The pull to level flight is a ? loop of constant radius. The figure is complete upon reaching level flight. Again, penalties are given for deviation from level flight or proper heading.

Take another deep breath and get ready for figure #3, the half Cuban. Actually, take the weekend off and I'll get to figure #3 on Monday.
 
I'm going out to practice this weekend, you have me inspired, although I might not be able to wait till Monday to do the half cuban and the loop

Cheers
 
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Flying the sequence - Figure #4

Primary Known 2018 - VAF

Well, Eddie in Australia, I hope you had a great time practicing this weekend. I suppose you tried a few half Cubans and loops. I hope they worked out OK. Notice that I have skipped figure #3. I did this on purpose. Figure #3 is a half Cuban which is really a 5/8 loop with a 45-degree down line tacked on with a half roll on that 45. You will do better half Cubans if you first understand what makes the perfect loop. Competition loops are not simple and there are a few things you need to know about how loops and partial loops are judged in order for you to be competitive.

Figure #4 is, of course a loop. RV entry speed for the loop can be anywhere from about 140 knots to Vne. The higher the entry speed, the larger the loop. Be careful to avoid exceeding Vne. You should give yourself a little margin for error there. Nothing in competition aerobatics requires you to exceed the design limitations of your aircraft. Stay within airspeed limits, CG limits and within aerobatic maximum weight limits!

The competition loop is a wind corrected figure which means that to the observer on the ground the perfect loop should be round, regardless of the wind speed or direction. Wind correction is only with regards to the roundness of the loop and not for the effect of any crosswind on the figure. Therefore, no deduction is given if the finish point is displaced relative to the start point in a direction perpendicular to the plane of the loop. I find that the perfect pull for the loop is between three and half and four Gs and G load should normally be eased up to less than 1/2 G at the top of the loop. No need to go higher than 4 Gs on the initial pull and if you use too little G you will find that the airspeed across the top of the loop can get quite low. Full loops must also begin and end at the same altitude or they will be downgraded. Loops must be flown with no visible crabbing and wings must be level at all times. The one point for every five degrees rule holds for both these cases. Any variation in the radius from one quadrant to the next can be downgraded a fixed number of points, generally one point for each change in radius. It can be more depending on the magnitude of the variation. A common error is for the vertical diameter of the loop to be larger than the horizontal diameter. This is often called an ?L? shaped loop. In general correcting for a headwind requires that a larger than normal radius is needed when going into the wind (the first and last quarter) and a smaller radius is needed when going downwind (the second and third quarter). There are many variations on the loop (immelmann, split S, Cuban 8, etc) but the basics still apply.

I'll get back to the half Cuban (figure #3) next. Now that you understand how to fly the perfect loop you can apply that knowledge to the half Cuban.
 
Flying the sequence - Figure 3

Primary Known 2018 - VAF

Now that we have discussed loops (Figure #4) we can back up and apply that knowledge to figure #3 which is a half Cuban eight. The first part is just 5/8 of a loop and should be wind corrected as we discussed earlier. At the completion of 5/8 of the loop you will be headed towards the Earth at a 45-degree angle and hanging from the seat belt. Pick a point on the ground as you establish this down line and drive to the point. There is a half roll to upright on this 45-degree line and the roll must be placed at the center of the line. The line starts when you first depart the looping radius and ends when you begin the pull out at the end of the figure. Points are deducted based on the variation from perfect placement of the roll at the center of the line.

--A visible variation - 1 point deduction
--If the lengths vary by 1:2 - 2 point deduction
--Greater than a 1:2 variation - 3 point deduction
--No line before or after - 4 point deduction
--No line before and after - 2 point deduction

If you do not have an inverted system in your airplane you may opt to roll immediately after the 5/8 loop and start the pull-out immediately following the roll. It would only cost you two points!

Finally, the pull out is just a 1/8 loop back to level flight. End of figure.
 
Flying the sequence - Figure 5

Primary Known 2018 - VAF

Figure #5 is called a competition turn or a competition 180. It is also a cross box maneuver in that it can be flown in either direction in order to bring the contestant to a more favorable position in the aerobatic box. For instance, should a strong crosswind blow the contestant towards the front of the box, a cross box maneuver such as the competition 180 can be used to move back towards the center of the box to avoid an "out" or merely to position the remaining figures in a more favorable position to be judged. (Judges do not like to see contestants crowd the near edge of the box as the true shape of figures is difficult to judge at that angle and can also cause undue strain on the necks of sensitive judges. :rolleyes:)

Competition turns are not to be confused with standard coordinated turns. In aerobatic competition, a turn is divided into three distinct phases: 1) establishing the bank using a roll on heading; 2) a heading change of 90?, 180?, 270?, or 360?; and 3) a roll back to straight and level flight while maintaining the final heading. Immediately after the roll to a bank angle of at least 60? is complete, the heading change must begin. Throughout the turn, the established angle of bank, rate of turn, and horizontal flight must be maintained. Turns are NOT wind corrected to have a constant radius. Therefore, in wind, a 360 degree turn will not close over the same point it began. As soon as the aircraft is on the exit heading, the heading change must stop while maintaining the chosen bank angle, followed immediately by a roll back to wings level using a rate of roll equal to the entry roll.

Commencing the turn before the bank angle is set will cost one point for every five degrees of turn completed before the bank angle is set. Setting the bank angle less than 60 degrees or changing the bank angle during the turn will also cost one point per five degrees. The rate of turn must be constant and the rate of roll into the figure must be the same as the rate of roll out at the end of the figure. A constant altitude must be maintained else a penalty of 1 point for a 100 foot deviation can be assessed and the bank must be held constant until the aircraft has completed the entire turn. Finally, the turn must be completed on the proper heading, that is after 180 degrees of turn in the above sequence.

I find that the RV makes the most predictable competition turns at high speed and at somewhat more than 60 degrees of bank. If you lollygag around the turn it is just too easy to let the bank vary and altitude control is more troublesome.

Now that you have used the competition turn to move to the center of the box we will begin the final figure in the sequence and by far, the most challenging figure of all... the aileron roll. :eek: Take a breather and I'll finish up the sequence tomorrow.
 
--No line before or after - 4 point deduction
--No line before and after - 2 point deduction

If you do not have an inverted system in your airplane you may opt to roll immediately after the 5/8 loop and start the pull-out immediately following the roll. It would only cost you two points!
To clarify: If you start the roll immediately after the looping portion, and pull out immediately following the roll, you lose two points, but if you held the downline after the roll and then pulled out you would lose four? So it sounds to me like symmetry before and after the manoeuver is more important than establishing the starting/finishing downline?

Second question: Any tips on keeping the nose from "wandering" while doing that roll? I find I can do a reverse cuban (45 nose up, roll inverted, 5/8 loop back to level) without issue, but rolling while on the inverted 45 downline always ends up with exiting the figure to one side. Maybe I should wait for the discussion on aileron rolls... :)
 
Flying the sequence - Figure 6

Primary Known 2018 - VAF

Figure #6 is an aileron roll. There are only two basic types of rolls in powered aerobatic competition, the aileron roll or slow roll and the snap or flick roll. But there are dozens of variations of those two figures. The aileron roll can be a two, four or eight point hesitation roll and it can be incorporated into basic figures as in the half Cuban eight, figure #3 of this sequence. A full aileron is the basis for all of those variations so I'll discuss it here.

On a horizontal line the perfectly executed aileron roll will remain on that horizontal line throughout the roll with no gain or loss of altitude and no change in heading. The roll rate will remain constant throughout the 360 degrees of rotation and the initiation and termination of the roll will be crisp, without a discernible bobble. Deviations in the rate of roll can be penalized by a one point reduction for every rate change. If you hesitate at any point during the roll it could be mistaken for a hesitation roll and earn you a hard zero for the figure! Over or under rotation and heading deviations are penalized by one point per five degrees.

RVs have non-symmetrical ailerons to minimize adverse yaw at positive angles of attack. When rolling with the stick forward as is required when executing a competition aileron roll the effect is to make adverse yaw worse. Because of this, rudder inputs are much more important when the stick is forward than when it is back. Let's discuss an aileron roll to the left: The first quarter of the aileron roll will require more top or right rudder as you approach the 90 degree point and the same rudder input will be required throughout the second 90 degrees as you feed in forward stick to maintain altitude while approaching the inverted position. Right rudder will STILL be required well past the 180 degree point to counter the effects of adverse yaw while inverted. Approaching the 270 degree point the right rudder is reduced and finally left rudder is applied to keep the nose up during the last quarter of the roll. The following graphic is borrowed from book by Alan Cassidy titled Better Aerobatics. (A fine read if you really want to get into this stuff!)



Master the control inputs as depicted by this graphic and you will be well on your way to mastering the aileron roll.

Upon completing the final figure of the sequence you should give three crisp wing dips to the judges and exit the aerobatic box with a smile on your face. :D

Much of the information I have provided in this series of posts is gleaned from the IAC Official Contest Rules which is available to IAC members HERE.

If you are not already an IAC member I hope you will join us and discover the thrill of aerobatic competition. Join HERE.

I want to leave you with a quote from Alan Cassidy which accurately describes the joy I experience while flying aerobatics. I hope you will feel the same.

"Ultimately, whether you fly for an airline, for the military or even with your best mate on a day trip to the next state, you lack freedom in the air. You are bound by tasks, procedures and limitations. The romance and pure joy of the unrestrained flight of birds are missing. Pure flying involves no application. It has no purpose other than personal fulfillment. It is selfish and pointless. It is also utterly inspiring and addictive. There is no other way of squandering large amounts of money on high-tech machinery that comes close to providing the three-dimensional freedom of expression and timeless joy of limitless pure flight. Cars, boats, yachts, jets... you can keep them all. They don't even come close."

Questions? Bring 'em on!
 
To clarify: If you start the roll immediately after the looping portion, and pull out immediately following the roll, you lose two points, but if you held the downline after the roll and then pulled out you would lose four? So it sounds to me like symmetry before and after the manoeuver is more important than establishing the starting/finishing downline?

Second question: Any tips on keeping the nose from "wandering" while doing that roll? I find I can do a reverse cuban (45 nose up, roll inverted, 5/8 loop back to level) without issue, but rolling while on the inverted 45 downline always ends up with exiting the figure to one side. Maybe I should wait for the discussion on aileron rolls... :)

Rob, I think you answered your own first question. As a bonus, this works in favor of those without inverted systems.

The discussion on aileron rolls does answer your second question in a way. Look at the graphic that describes the control inputs during an aileron roll. Start at the 180 degree point and you will see that a left roll from inverted requires lots of RIGHT rudder to maintain a coordinated roll. This is due to adverse yaw which is countered by rudder OPPOSITE the direction of roll when inverted.
 
Ron, thanks muchly. I bought Cassidy's book this year, but haven't got to the article on aileron rolls yet... :) I know what inputs I need, and the graphic you show above confirms it... The catch is getting my feet and hands to coordinate it all together at the right time. That's why we practise... :)
 
That's the way you do it (youtube)

I was hoping Ron would put in a video along with the great explanations of each maneuver. However, this RV one might do: https://www.youtube.com/watch?v=PhJHdb9k7Ho Note that I have an inverted system, so I can draw a 45 down line on the 1/2 Cuban 8.:cool:
Time to go have more fun,
Bill McLean
RV-4 slider
lower Alabama
 
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