IMAC aerobatics buyers' guide

Model Airplane News, Apr 2001

The International Miniature Aerobatic Club (IMAC) has been around for more than 25 years, and its popularity has unquestionably grown. Look in any RC model airplane publication, and you'll find more than just a few colorful IMAC airplanes to choose from. Aerobatic competition is challenging for the pilot and entertaining to spectators. Now more than ever, the opportunity to become involved in IMAC aerobatics is wide open to anyone who wants to improve his piloting skills. If you're looking for a new challenge or want to feel a renewed sense of accomplishment that's as great as or greater than the one you felt when you first soloed your RC trainer, then consider this wonderful and rewarding aeromodeling pastime.

The introduction of almost-ready-to-fly (ARF) and almost-ready-tocover (ARC) aircraft has redefined our hobby. Instead of spending weeks and months building and finishing a model, we can now enjoy bench time that has been reduced by prebuilt aircraft kits to days-even hours. ARFs and ARCs are not likely to totally replace kit-built models, nor should they, but for someone who has little time to build, they are a great way to get to the most exciting part of the hobby: flying!

We've collected as much information as we could on the plethora of prebuilt IMAC-legal airplanes on the market today. Though not a complete list-new products are being introduced almost daily-we're sure this guide will be a helpful source for finding the best IMAC aerobatic airplane for you. If you want to join all the fun and excitement IMAC has to offer, this guide will put you on a straight and level line as you enter the "aerobatic box"!

What is IMAC?

IMAC's objective is to duplicate full-scale sport aerobatics using miniature RC aircraft in a realistic manner that is both challenging for the contestants and intriguing for spectators. All AMA regulations apply to RC fliers. The type of equipment fitted to the aircraft is not limited, nor is the number of controls. IMAC competition is open to all aerobatic monoplanes and biplanes that are replicas of full-size aerobatic competition aircraft. To maintain separate levels of difficulty, there are three classes: Sportsman, Advanced and Unlimited. The aircraft are flown within an imaginary aerobatic space known as "the Box." The maneuver sequences (groups of maneuvers to be flown) are the same as those used in full-scale International Aerobatic Competition (IAC). The sequences are grouped into two categories-Known and Unknown.

The Known compulsory sequences are similar to IAC sequences but are modified to better coincide with model aircraft capabilities and pilot skill levels. The sequences change annually and are printed in the IMAC competition newsletter each spring, along with any updated rule changes.

The Unknown sequences consist of 12 to 15 maneuvers designed for contestants to fly without prior practice. They are assigned on the day of the contest (or the night before) to allow pilots to visualize them. The contestants' flight order is established by a random drawing.

Flight Pattern

A contestant must fly the entire flight according to the established flight schedule for his class and in the sequence listed. Maneuvers that are performed out of order are not scored. Takeoffs and landings are not judged, and it is not necessary for the judges to see the aircraft take off or land. No flybys are allowed during an aerobatic sequence. If a flyby breaks the sequence order, any omitted maneuver and the next maneuver in the sequence earn zero points as a penalty. Whenever the entire airplane is observed flying past any of the box's boundaries or markers, this is noted and the pilot's score is penalized.

3-Minute Freestyle

The 3-minute Freestyle is known as "Show Time" and is a separate event. It is an unrestricted, individually created sequence in which anything safe goes! It is scored on:

Originality. Creating new figures, novel combinations of old figures, novel use of the aircraft, an element of surprise and good use of the full aerobatic zone.

Versatility. Displaying a wide variety of maneuvers.

Harmony and rhythm. Choreographic characteristics of sequence.

Execution. The quality of flying and the pilots ability to hold the judges' and spectators' attention.

Four judges evaluate contestants on each of the criteria separately and rate them on a scale of 0.1 to 10 for a maximum total of 40 possible points.

The Aerobatic Box

All maneuvers must be flown In front of the judges in an area that is 60 degrees on either side of the centerline, to the rear comers of the box, 75 degrees to the front comers and no higher than 60 degrees. The minimum altitude is no less than 20 feet. The aircraft must rock its wings before entering the box and again just after leaving it to show the judges the beginning and the end of the sequence. The pilots may also announce the beginning and ending of sequences to alert the judges. There is no time limit while In the aerobatic box, but there is a time limit for starting the engine, taking off and entering the box. All classes' maneuvers are scored on a scale of 10 to 0. Points are deducted for imperfections in positioning, heading, track and attitude. Half (.5) points are also used in judging. Excessive or unrealistic speed and high G-force maneuvers are downgraded. The degree-of-difficulty factor (K-factor) values are assigned to individual maneuvers based on the current FAI catalog of maneuvers and are modified as needed by IMAC. The contestant's score for each maneuver is multiplied by that maneuver's K-factor. The flight score Is the sum of all the "K-factored" scores.