RADIO CONTROL AEROBATICS
Ron Van Putte, 111 Sleepy Oaks Road, Ft. Walton Beach, FL 32548
The FAI F3A Rules Vote
The big news is the vote on FAI F3A rules: the unlimited engine displacement proposal passed. Weight and noise limits remain the same — five kilograms (11 pounds) and 96 dB, respectively. The model must fit in a two-meter-by-two-meter box (about 78 3/4 inches on a side). Interestingly, the proposal to change the box limit from 60" to 75" never even came up for a vote.
The new rules will not go into effect until 1996, so we face an interesting transition period. Many designers and fliers will experiment with different airframes and powerplants; it may be reminiscent of the shift when turnaround-style flying was first introduced. Biplanes? Who knows.
One trend already being discussed is trying the new supercharged YS .91 four-stroke in airframes designed for .61 two-strokes. That could make models like the .61 Jekyll, Meridian, Elite, and Desire more competitive.
Four-Stroke Engines: Necessary or Not?
Current wisdom says that to compete in RC aerobatics you must have a supercharged 1.20 four-stroke and burn at least 35% nitro. Bull — that's not true. It might help those aiming for the highest levels of Masters and FAI competition, but historically a four-stroke has never been in an F3A World Champion's model when he won. Nor is a four-stroke necessary to compete successfully in AMA Novice, Sportsman, or Advanced classes.
Letters from Readers
Letter from Lyle Sams (Kingsport, Tennessee)
"I have flown Pattern for lots of years since 'the reed days.' I have raced boats, midget cars, and karts. A known fact is that you cannot beat the almighty cubic inch.
"The AMA engine rules as they stand are the most one-sided thing I have ever heard of in any kind of competition. Whether you want to use two cycle or four cycle, the cubic inch should be the same, with maybe a limit. I think the present rules are killing the interest in Pattern. I saw it get into a slump a few years back and it has never fully recovered."
Based on preliminary results of the National Society of Radio Controlled Aerobatics (NSRCA) rule-change survey, I expect the NSRCA will propose that the AMA adopt an unlimited engine displacement rule, effective January 1996.
Letter from Dana Moreland (Encino, California)
"After reading your June 1994 Model Aviation Aerobatics column, I have a third topic of concern for a beginning Pattern flier (other than the model and radio; RV/P): Which engine should he use?
"I have been flying RC sport models for four years now and have decided to try my hand at competition, flying Novice Pattern. I have decided on an Ultra Sport-40 kit, controlled by a Futaba 7UAF radio. Which .45-.46 c.i. engine should I use? — The choices are many, over 25 different ones. They range from $53 K&B .45 R/C Sport to the $200 O.S. .46SF ABC with pump.
"Which .60-.61 engine would you recommend for the Ultra Sport 60 kit for the beginning Pattern flier? Again, the choices seem many, from a $100 Fox to a $400 Hanno Special.
"I would also like to know if you would recommend for or against the following features in an Ultra Sport kit built to fly in Novice and/or Sportsman: 1) A tuned pipe 2) Retractable landing gear 3) Aileron differential 4) Inflight mixture control."
Engine Recommendations for Beginning Pattern Fliers
For an Ultra Sport 40 flown in Novice, I recommend an ASP .46. The ASP is reliable, low-priced, and provides more than enough power to complete the Novice maneuver schedule comfortably. While other .45-.46 engines may produce more power, that extra performance is unnecessary at this level, and the money saved can be spent on fuel and practice.
For the Ultra Sport 60, I recommend the ASP .61 for the same reasons: reliability, cost-effectiveness, and adequate power. Another practical consideration is parts availability; the ASP distributor (ISC International Trading Co., Inc.) maintains a good stock of spare parts for repairs after hard landings. I have no financial interest in ISC; I speak from the perspective of a hobby dealer and value-conscious flier.
Responses to Dana's Feature Questions
Tuned Pipe
A tuned pipe is not really necessary for Novice and Sportsman. It is heavier and more complicated to install than a muffler, and on models like the Ultra Sport it cannot be hidden inside the fuselage. Tuned pipes are generally quieter than some mufflers and can offer a power boost, but Novice and Sportsman schedules do not require that extra power. For an Ultra Sport 40 in Novice, skip the tuned pipe. For Sportsman, consider a tuned pipe only if you want the feel of a higher-performance setup.
Retractable Landing Gear
You can fly a model with retractable landing gear in Novice, but the gear must be left down. Retractable installations can improve flight handling and reduce trim changes with airspeed, but they are difficult to install well. I do not recommend retractable gear for models like the Ultra Sport unless you have the skill and patience to do a solid installation.
Aileron Differential
Aileron differential helps reduce adverse yaw and makes a model roll better. It's straightforward to implement mechanically or in the transmitter. Tuning the correct amount of differential takes time, but it's not difficult and is a useful adjustment.
Inflight Mixture Control
Inflight mixture control is a nice-to-have, not a necessity. There have been times I wished I had it, but once a flier learns how an engine behaves in different weather conditions, inflight mixture is generally unnecessary.
Practical Advice
When considering features, realistically assess their practicality. Many times you'll find you want a feature more than you need it. Make choices based on reliability, simplicity, and what truly helps you fly and practice effectively.
Transcribed from original scans by AI. Minor OCR errors may remain.
