LIGHT IS BETTER!

-By Clay Ramskill

We all know that airplanes are created as light as possible, consistent with structural strength. To most of us, this is a pretty obvious reality -- after all, they use aluminum, not cast iron, right? But ALL the advantages of a light airplane may not be so apparent.

So let's have a peek -- we'll start with the most obvious.

Load carrying capacity. Hey, this one's easy! All other things being equal, the lighter plane can carry more load. Big deal? Well, maybe yes -- how about more fuel, or a larger battery, or bigger servos?

Climb performance. Again, everything else being equal, the lighter plane will climb quicker. For us, that means better vertical performance for acrobatics, among other advantages.

Turning performance. How tightly a plane turns is one more area that is directly related to weight. With all else being equal (i.e., speed, angle of attack, etc.), the lighter plane will turn a smaller diameter circle.

Acceleration. F = MA, remember? Again, a direct relationship exists, the heavier plane (more mass!) being the loser!

Stall speed. Ok, this one's not a direct relationship. But without going into the math, it's a fact that a heavier identical plane will have a higher stall speed. And it follows, then, that both take off and landing speeds will be higher for the heavier plane.

Top speed. Really? Yes, indeed! -- but not by much! Every wing produces drag in the process of getting lift (the lift vector is ALWAYS tilted back a bit with respect to the line of flight). So, the more the lift required for a heavier plane, the more drag will exist, cutting top speed somewhat.

All the above itms can be calculated accurately, with the right formulas and an ordinary calculator. But some of the "light is better" advantages are more subjective -- words like "quicker" or "more responsive" come to mind. And heavier planes? Have you heard the terms "dog" or "slug"?

The wind/turbulence factor: Ah, you say, here comes the BAD part! Well, yes -- and no. The lighter, more responsive plane will react more quickly to wind gusts and shifts. However, self-correcting and any corrections you can make can also be effected sooner with the lighter plane. And note - problems with wind, turbulence and gusts is more related to wing loading than just to weight itself. If we took some weight out of a plane, then lowered the wing area proportionally, then the planes behavior in the wind would remain about the same.

We've all seen a very light plane being blown around badly in gusty conditions -- but this is more a result of the plane's design, and is most certainly a result of lower flying speed.

One more comment on lower aircraft weight. If you can save weight somewhere, you may be able to save even more somewhere else! The lighter your plane, the less structural "beef" is required. An obvious example would be landing gear -- a lighter plane can use lighter landing gear. But this principle will apply all over the plane's structure.

Another point of contention here could be crash survivability. But the fact is, crash damage is a result of how well or how badly a plane can absorb the energy that must be dissipated in a sudden stop. That energy is, again, related to the planes weight - less weight, less energy to absorb in the crash! If you add in the point that the lighter plane has a good chance of crashing at a lower airspeed, then the light plane actually may suffer LESS damage in the same circumstances! [Future articles will give you some details about weight placement and how to cut weight in typical models.]

Site maintained by QSoftWorks
Last Update: 10/12/97