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Importance of Low Weight for Successful Model Aircraft Flight

The Critical Importance of Low Weight for Successful Model Aircraft Flight by Tim McKay

Perhaps no other factor affects the flight performance of a radio control model airplane than aircraft weight. You can demonstrate this for yourself. Take one of your favorite RC planes, one you know well, and fly it through a series of normal maneuvers. Add some additional weight to this model and fly it again. The lighter version will fly better, take off in a shorter distance, climb out quicker and handle in a more pleasing fashion.

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This effect of weight on flight performance applies to all aircraft. Minor differences in weight for the same aircraft type are usually not noticeable. But if you are not paying attention to aircraft weight as you design a model aircraft or construct one from a kit or set of plans, excess weight can easily creep into your finished project.

In full size aircraft, weight is a major factor affecting flight operations. A typical jet airliner can have up to one third of its weight in fuel alone. If you take off in a Boeing 747 for a long flight, the jet transport is actually too heavy to safely land right after takeoff. The assumption is the aircraft will burn off fuel and become lighter during flight, allowing for a safe landing at a lower weight once at its destination.

With most radio control model airplanes, and especially electric powered RC models, there is no real difference between take off and landing weight. We therefore have to be careful to build the model as light as possible. Once the airplane is built, its flight weight is essentially fixed.

The question comes up as to what is an acceptable weight for an RC model plane to fly well. The answer is “it depends.” You need some method to relate total aircraft weight to the size of the model. This is usually done by making a ratio of the aircraft weight in ounces per square foot of wing area.

Wing loading, by itself, is not enough to properly predict the flight characteristics of a model airplane. Rather, wing loading is an indicator of flight performance that must be considered with other aircraft design factors.

Wing shape, airfoil and aircraft size all play a large role in determining flight performance. A trainer model plane with a Clark Y airfoil will tolerate a higher wing loading as opposed to an aerobatic model with a thin wing cross section.

A larger plane can typically handle a higher wing loading than smaller aircraft. For example, a wing with an area of 2000 square inches could support a loading of possibly 35 ounces per square foot, while a 500 square inch wing could handle perhaps 20 ounces per square foot. Note that 144 square inches equals one square foot.

Very lightweight micro sized indoor electric powered model airplanes represent a special case for wing loading and weight considerations. For truly miniature indoor RC planes, total weight is the governing statistic. The tiny electric motors and propellers produce limited thrust, and the model is essentially designed around the power plant.

Some of these micro flyers come with a flying weight of just 18 grams. There is really no point in figuring out the wing loading on a miniature model of this nature. Rather, the guiding principal is to keep everything as light as possible. Modelers who have added just a piece of tape to this genre of aircraft prevented take off due to the minor increase in weight.

We can use these aircraft performance characteristics to our advantage. When building any model airplane, and especially micro indoor flyers, keep the weight to an absolute minimum. If you are designing the model, “build in lightness” with the least amount of structure required. When building any model pay attention to the grade of balsa or other building material being used to conserve weight wherever possible.

Model aircraft weight is a critical aspect for safe flight and a predictor of performance. Few actions will more quickly and easily improve a model’s airborne characteristics than reducing the airplane’s weight. Keep this insight in mind as you design, construct and evaluate the flying performance of your RC airplane fleet.

Tim McKay is an accomplished model airplane designer, builder and pilot. Find more information, flight reviews, building tips, free plans and over 30 instructional model aircraft videos at: => http://www.IndoorFlyingModel.com

 

 

 VINTAGE Hirtenberger HP 49 VT 4 Stroke RC Airplane Engine. ( Made in Austria )

 VINTAGE Hirtenberger HP 49 VT 4 Stroke  RC Airplane Engine. ( Made in Austria )
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