Perhaps you've been to the local flying field, visited a hobby shop, or spent hours
watching "Wings" but for whatever reason, you now have the burning desire to fly an
R/C airplane. And not just any airplane but a model of one of the famous WW II
warbirds or a high performance aerobatic aircraft.

Your motivation for getting into this great hobby is similar to what got many of us
started. The path you take will have a great impact on whether you reach your goal or head down the road to unnecessary expense and frustration. All to often we hear of the enthusiastic newcomer that builds a beautiful scale warbird for their first model only to completely trash it after a maiden flight lasting all of 20 or 30 seconds. Usually, the newcomer is so upset by this event that he or she quits right then and there.

If you want to earn your wings flying full-scale aircraft, you'd probably agree that it
would be ludicrous to expect to start off with an Extra 300 for your basic flight training. Well it makes no more sense in the R/C world either.

The appropriate airplane for basic flight instruction for either full scale or R/C is a high
wing trainer. With the next few hundred words, I'll attempt to explain why that is. Most of the attributes that make a plane great for the fighter or aerobatics role make it unsuitable for the basic trainer role. Two important attributes are stability, and stall
characteristics. Let's look at these in more detail and see how they differ for each role.

Stability - There are three characterizations of stability: positive, neutral and negative stability.

A plane that is said to have positive stability will eventually return to straight and level
flight on its own (with enough altitude). This is a very desirable trait for a trainer as the plane wants to fly straight and level and it requires deliberate and significant input from the pilot to get it to deviate from that flight regime if it is trimmed correctly.

The design features that impart this virtue to a trainer are:

• Flat bottom airfoil
• Constant chord wing
• Generous dihedral
• Long tail moment
• High wing configuration
• Light wing loading

I think that it is safe to say that you won't find these features incorporated in the design of warbirds or aerobatic types.

Neutral stability is the characteristic of a plane that will go where you point it and
continue on the directed heading and attitude (even into the ground) until the pilot's input causes it to go off on a different heading or attitude. Planes with neutral stability don't have a natural inclination for straight and level flight. More experienced pilots consider this to be a virtue and the plane is said to groove well. But at the newcomer stage a plane of this type can quickly get ahead of you.

Negative Stability. This is the characteristic that has created many proverbial smoking
holes during the history of manned and R/C flight. Airplanes that seem to have a mind of there own and will dart around the sky like a dog looking for a spot to relieve himself have this type of stability. Actually, instability would be a better word as the last thing a pilot would say of these aircraft is that they are stable.

You may think that this is a very undesirable characteristic but it does have its place. The hottest new jet fighters have this feature designed in to enhance their maneuverability. All it takes are a couple of high-powered on- board computers to help the pilot keep from adding to the world's supply of smoking holes. The legendary WW I Sopwith Camel was considered to be a very dangerous aircraft to fly but a great fighter by those pilots who lived long enough to learn how to fly it. Unfortunately, many didn't. With its big rotary engine mounted on its short nose, this plane was unstable but none of its contemporaries could out-maneuver it when flown by a pilot who learned how to tame it. If you would like to experience the thrill of flying a model with negative stability, throw a bunch of weight in the tail of a normally well-mannered plane (but one you're willing to offer up as a sacrifice). Those of us who have can state without much fear of contradiction that this isn't a desirable trait for a trainer.

Stall characteristics - No were not talking about what the engine does when it runs out of fuel. Our discussion refers to an aerodynamic condition that causes the wing to stop providing lift. When aerodynamic stall occurs, the consequences can be anywhere from benign to sever depending on the aircraft. Typically, a well-designed high wing trainer will have a very gentle stall when forced into one. The nose of the plane will gently drop, the wings will stay level and the plane will regain speed and resume normal flight. The other end of the spectrum is a stall that occurs without warning and instead of the nose dropping gently, one wing will drop and the plane will enter a vicious snap to the right or left. If the pilot doesn't react quickly, the plane will then go into a spin if at altitude or snap into the ground at low altitude as when you are on final approach. There is a .25 size Spitfire ARF on the market that has some of the nastiest stall characteristics I've ever experienced.

Wing design and wing loading play a role in the stall characteristics of an airplane.
Trainers generally have a constant chord wing with a flat bottom airfoil that generates a lot of lift at low speeds. With a light wing loading, this type of wing has to be forced into a stall. And as the stall propagates outward from the wing root on a constant chord wing, the wing will remain level.

As the builders of WW II fighters optimized the designs for speed and maneuverability,
they typically have a tapered wing with an airfoil shape that causes less drag than a flat bottom one but also less lift at low speeds. Models of these planes generally share these features. In addition both the full scale and R/C versions of these planes have
significantly higher wing loadings. Putting all of this together means that these models
will stall at higher speeds with little effort on the part of the pilot. And because the stall propagates inward from the wing tip on a tapered wing, it is highly likely that the plane will fall off to one side rather than straight-ahead resulting in a tip stall. Tapered wings can be designed to avoid tip stalls by incorporating "wash-out" on the wing tips. This means that the angle of attack of the wing tips is at minus 2 or 3 degrees when the rest of the wing is at zero degrees. You won't find this on an aerobatic design because it works against you when the plane is inverted. My Ohio R/C Chipmunk has this feature and it is one reason why it won't do an outside loop. I can't prevent it from snap rolling as I enter the loop.

No one deliberately designs a plane to have a high wing loading but with WW II fighter
models, it is hard to avoid. Even if a particular model doesn't have what's considered a
high wing loading, it most likely will be greater than that of a comparably sized trainer.
Many of the maneuvers performed by aerobatic airplanes require that one wing stalls first for proper execution so they are designed that way. Snaps and spins are the expected repetoir for these planes and they are designed accordingly. Good characteristics for aerobatics, lousy for basic training.

In summary, a good trainer has positive stability and gentle stall characteristics. This will be a plane that is considered forgiving of pilot error. On the other hand, a typical warbird or aerobatic type has, at best, neutral stability and a manageable stall or worse, have negative stability and an aggressive stall. Either way, they will be an unnecessary impediment to learning how to fly an R/C airplane. To be on the safe side, check with an experienced instructor before buying your first model. Most instructors have flown just about every trainer variation that has taken wing and we love to have the chance to express our opinions.

By the way, if you still want that P-51 kit, go ahead and get it if you have your heart set on it. Just do yourself a favor and put it aside for awhile. It just might provide the
motivation you need to learn how to fly with a trainer, then learn how to handle a gentle low wing tail dragger with your second model. If you get this far, and we'll do all we can to insure that you do, you just might be ready to tackle that P-51.