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Ailerons Can Be Flaps Too!

Flaps are popularly used for full-scale aircraft as a means of altering the lift-to-drag ratio of a fixed wing, especially at low speeds. Small flap extensions, say 10 tex2html_wrap_inline122 , can increase the lift of an airfoil, allowing shorter takeoffs and much slower landings. Large flap extensions, typically up to 40 tex2html_wrap_inline122 , markedly increase the drag of the airfoil, allowing for slow landings with steep, predictable glide slopes. In fact, many aerodynamically-clean aircraft practically require some extension of flaps to land easily at all! Even small general aviation planes like the venerable single-engine Cessnas will float along seemingly forever without flaps, but have a markedly steep glide path with full application of flaps.

Radio-controlled models can often benefit from the same application of principles. Many of us have had one model or another that was very fast, very ``clean'' - and almost impossible to slow down to land predictably or reliably. Scale models are notorious for this kind of behavior, especially models with high wing loadings such as WWII warbirds.

Most modelers don't add flaps to their planes, however. One reason is the popularity of simple 4-channel radios; however 6-channel radios are arguably even more common nowadays, and most of those pilots still never use the 5th or 6th channels. Increased complexity in wing construction is certainly an issue, especially since most kits don't include plans or materials for flap construction. So what is one to do?

One neat way to easily retrofit flaps on your plane is by the use of flaperons - a term implying use of ailerons as flaps. To use flaperons, you will need a radio with mixing capabilities (i.e. just about any ``computer radio'') or will need to install a mechanical mixer. The structure of the wing remains intact, since the ailerons were presumably there in the first place!

There are, however, some issues that must be addressed when using flaperons, namely 1) Adverse yaw while the ``flaps'' are down, and 2) Pitch trim changes when lowering the ``flaps''. How shall we deal with these issues?




next up previous
Next: Dealing With Adverse Yaw Up: Front Page Previous: Club Instructors are:

Craig Kulesa
Wed Jun 30 22:29:14 MST 1999