Author: John Glezellis
Edition: Model Aviation - 2012/02
Page Numbers: 119,120,121
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Radio Control Scale Aerobatics - 2012/02

Introduction

Because the 2012 flying season is approaching, this month’s column is dedicated to Maneuver 6 from the International Miniature Aerobatic Club’s (IMAC) Official 2012 Sportsman Known sequence: a Stall Turn with a Full Roll Down.

In this sequence, 10 different maneuvers must be performed by the pilot in a specific order. Each move has a different level of difficulty, so each exercise plays a different role in how scores are tabulated for a total flight score. Although a seasoned pilot will be able to perform all maneuvers well, it is important to understand the basics behind how one can change a flight score.

As an overview, I will first look at how each movement in a given flight is tabulated, using the maneuver of the month as an example. Then I will examine the key inputs for performing Maneuver 6 and offer a few setup tips that will benefit you, the pilot.

What is K-Factor?

Each basic move and rotational element in the FAI Aerobatic Catalogue is assigned a difficulty coefficient, also known as the K-Factor. The basic shape comes from each family (the first value) and rotational elements are given a K-Factor according to their flight direction and extent.

In the basic form, a movement such as an inside loop will have only one value. Compound moves have separate K values that are added together. Each component of the exercise is given a Catalogue number, which tells us which family, row, and column it comes from so we can see the individual value of each part.

If a pilot performs a low-K maneuver very well but makes a mistake on a higher-K maneuver, another pilot who performs both moves in a mediocre fashion may actually earn a higher score. This is one of the ways top pilots separate themselves from good pilots, especially when flying an Unknown program.

Unknown programs are usually given to contestants the night before they are to be flown and cannot be practiced. Each pilot has one chance to perform the sequence in front of a panel of judges.

FAI Aresti System (Condensed)

Scale aerobatics sequences are based on a catalog of maneuvers defined by the FAI (Fédération Aéronautique Internationale) for full‑scale aerobatics. The catalog consists of nine (9) families of figures:

  • Family 1 – Lines and Angles
  • Family 2 – Turns and Rolling Turns
  • Family 3 – Combinations of Lines
  • Family 4 – (Not in Use)
  • Family 5 – Stall Turns (Hammerheads)
  • Family 6 – Tailslides
  • Family 7 – Loops and Eights
  • Family 8 – Combinations of Lines, Angles, and Loops
  • Family 9 – Rolls and Spins

Under the Catalogue number are separate elements that represent each part of the move and show which family they come from. For example, the stall turn with a full roll down is represented by two catalogue lines:

  • The first line starts with 5 (Family 5). The subsequent numbers indicate Row 1, Column 1, giving a difficulty coefficient of 17.
  • The second line is 9.1.5.4 (family 9). The value here is 8.

Seventeen plus eight equals a total K of 25 for the maneuver. The score you receive for that figure will be multiplied by this K value.

Flying the Stall Turn with a Full Roll Down

When looking at a sequence, pay attention to which moves come before and after each maneuver. The best routine will look smooth and graceful and will not force the pilot or the judges to rush.

To fly this maneuver:

  1. Align the airplane parallel to the runway.
  2. Apply ~90% throttle and perform a gentle radius to establish a vertical upline. Note the size of this radius because the exit radius should match it.
  3. Once vertical, show a large line segment. The full roll on the downline must be centered, with time and distance shown both before and after the roll. I recommend a line segment of at least 600 feet when flying a 40% scale aircraft.
  4. At the top, reduce throttle and wait for the airplane to nearly stop. Apply full rudder so the airplane pivots around its CG; when the airplane begins to head down, release rudder so a clean 180° pivot has occurred.
  5. Establish a downline, perform a full roll in the desired direction, show another line segment, and then pull out to exit in upright level flight.
  6. Apply throttle as needed to keep a constant speed throughout the maneuver.

If the stall turn isn't performed near the end of the aerobatic box, the pilot may be pressed for time and have to rush the following loop or other figure in order to center it. Plan the sequence so you have adequate room and time for each element.

Scoring and Penalties

  • Rotational errors: If the roll is centered and the stall turn and radii are correct but there is a 10° over-rotation in the roll, pilots are penalized one point per 10° of error.
  • Flight path: Strong crosswinds will show up in the flight path scoring. The airplane must be angled into the wind so that the flight path is vertical. If not, points will be deducted at a rate of 0.5 point per 5° of deviation.
  • Stall turn quality: In a perfect stall turn you should see the airplane rotate around its CG. If it does not and instead performs a "flyover," points are deducted.

Don't give away easy points by leaving obvious flight-path or rotation errors uncorrected.

Control Setup and Exponential

If your airplane is sensitive to control inputs, you may have too much control travel or not enough exponential. Adding exponential softens the stick response around center while allowing full travel near the extremes.

  • Note on radio systems: JR radios use positive (+) values for exponential; Futaba uses negative (–) values to obtain the same effect. Always consult your radio manufacturer for exact setup guidance.
  • Recommended starting values:
  • Aileron exponential: ~20%
  • Elevator exponential: ~20%
  • Rudder exponential: ~35%
  • Aileron travel: ~15°
  • Elevator travel: ~12°
  • Rudder travel: ~45°

You will likely need more rudder to execute the pivot and stall turn, but excessive deflection on other surfaces can make precision difficult.

Conclusion

Understanding how moves are tabulated and how each component of an exercise adds difficulty is as important as flying the figures themselves. This month’s maneuver combines a stall turn with a downline roll; knowing its K-Factor, the scoring risks, and proper control setup will help you improve your performance.

Now get out and start practicing — and always remember to have fun! — JG

Sources

Transcribed from original scans by AI. Minor OCR errors may remain.