Radio Control: Aerobatics

RADIO CONTROL AEROBATICS

Rick Allison, 26405 SE 160th St., Issaquah WA 98027

We pick up where we left off on our discussion of basic flight maneuvers. Having previously chewed our way through stall turns and loops, this installment considers Immelmanns, Cuban eights, and rolling maneuvers.

As you progress up the Pattern skill ladder, basic maneuvers constantly reappear as the elements that compose the more complex maneuvers found in higher-skill classes. Spend the time to master the simple fundamentals — they won't go away. If you can't do a decent stall turn, a Figure M with 1/4 rolls is going to be a struggle to learn.

Immelmann Turn

The Immelmann is one of the first true hybrid maneuvers, combining elements of two classic aerobatic families: loops and rolls. In its basic form as a center maneuver it consists of a half loop followed immediately by a half roll to upright flight. Looping rules apply and downgrades result for poor entries or exits.

Key points:

• Begin from a straight-and-level entry.
• Perform a half loop and finish precisely over the point where it was started (the center flag).
• Do the half roll immediately after the aircraft comes level in the inverted position.
• The maneuver finishes in straight-and-level flight on a heading 180° from the entry heading (if entry was parallel to the flight line, the exit will be parallel but opposite).

Common mistakes and tips:

• Do not center the half roll on the pilot; the roll center is slightly displaced past the maneuver center. Centering it on the pilot produces a "buttonhook" effect or a roll on a slight up line — both are penalized.
• A good, strong engine is important to maintain airspeed over the top. The most common fault is losing heading or dipping during/after the roll from inadequate airspeed.
• Rolling to the right (against engine torque) often helps hold the nose up better.
• Always form the habit of straight entry and exit lines. The AMA Competition Regulations state: "Maneuver entries and exits ... will be at least 15 meters in length." A missing entry/exit line carries a mandatory 2-point downgrade.

Cuban Eight

The Cuban Eight is a symmetrical hybrid maneuver made up of rolling and looping segments. Symmetry is critical: what you do on one side must be mirrored on the other in size, shape, and position.

Description (basic Cuban Eight):

• From a straight-and-level entry, perform a 5/8 loop to a 45° inverted down line.
• At the midpoint of that down line, perform a half roll (centered on the judges).
• Continue the 45° line into a second 5/8 loop to another 45° inverted down line.
• Perform a second half roll centered at the midpoint of the second line (and centered with the first roll and the judges).
• Finish with a 1/8 loop to straight-and-level exit.

Notes on classes and occurrence:

• The full Cuban Eight appears in the Sportsman class.
• The Half Reverse Cuban is in the Novice class.
• Variations of full and half Cubans appear in Advanced, Masters, and FAI schedules.

Wind correction and handling:

• The maneuver must be wind-corrected so the ground projection and geometry remain correct: round loops, centered intersect point, and symmetric halves.
• In a tailwind, you may need more elevator input over the top; the downwind 45° descent will be flown slightly steeper in front of the judges than the upwind descent.
• In significant breeze you may need partial to full throttle in upwind descents and/or rudder into the wind with a crosswind component.
• Adjust the shape of the loops so the wind’s effect on the aircraft’s track produces the same ground projection as in calm air.

Common errors:

• Flattening the bottoms of the loops.
• Over- or under-pulling the 45° descents.
• Habitually rolling late or early.
• Making the second loop larger than the first.
• Performing the whole maneuver off center.

The Cuban is lengthy and composed of many elements, so it is easy to make mistakes — and judges are strict. Respect the maneuver, practice it often, and practice it in many wind conditions.

Rolls

Rolls come easily to some pilots and are difficult for others. When the aircraft goes inverted, some pilots’ minds seem to switch off; stay mentally in the cockpit and think upside down.

General roll advice:

• Watch the wings and fuselage angle relative to the horizon; use elevator to hold heading and a horizontal line.
• All airplanes need a small amount of elevator input to maintain altitude through consecutive rolls. Methods vary: a quick shot of down elevator on inversion, or alternating down/up as the airplane switches sides (a rowing motion). Both can work — keep the rate constant.

Three Horizontal Rolls

For the Three Horizontal Rolls, rhythm and a consistent roll rate are critical.

• The roll rate should be slow enough that pilot and judge can follow it. Stretching rolls to five seconds or more was common in older styles but is impractical for turnaround flying.
• Rolling to the right often works better, but use what works for you.
• Aileron differential (more up aileron than down) should be tuned to achieve a nice axial horizontal roll. This setting is often a little different (usually less) than what works for vertical rolls.

To check differential using a Half Reverse Cuban Eight / Pattern Split-S style maneuver:

1. Pull to a 45° up line.
2. Half roll, continue the line, and 5/8 loop to level flight.

• If the tail yaws in the same direction as the roll, increase differential.
• If the tail yaws opposite the roll, decrease differential.

Placement and faults:

• The center point of the Three Horizontal Rolls is the inverted portion of the second roll.
• Common faults: off-center placement, gallops in elevation, improper altitude.
• Center the maneuver in the bottom half of the aerobatic frame. Too high scores low; too low makes it hard to roll fast enough and invites "roll rate increase taper."

Straight Inverted Flight

Straight inverted flight is more an exercise than a dramatic maneuver. Think of it as a two-point roll:

• Roll in on a line, fly a straight inverted line in the middle, roll out on a line.
• It looks better and scores higher to roll in and out slowly and gracefully.
• Keep the roll rate the same on both ends — this is an easy place to lose points, and judges will notice if you mess it up.

Common Themes and Closing Thoughts

We’ve covered lines, entries and exits, straight-and-level flight, stall turns, loops, rolls, Cubans, Immelmanns, and inverted flight — the basic building blocks of Pattern flying. Snaps and spins will be a future subject.

All advanced maneuvers are combinations of these elements. Think of them as a giant pizza menu in the sky: mix and match elements to make new maneuvers. The Aresti catalog used by IAC and IMAC organizes maneuvers this way: each element has a "K factor" difficulty, and the total K is the sum of the elements.

If you get a decent grip on the basics described here, you can call yourself an aerobatic pilot without blushing, and you’ll be well prepared to move on to more complicated maneuvers. You won’t be intimidated by long lists of strange names — you’ll see them as new combinations of familiar friends.

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