Chapter 6 : Choosing My First Model Airplane

The main intent of this chapter is for the beginner to choose the correct ways to start his/her hobby with minimal error. Of course, there is no such thing as perfect ways to start this hobby. Just avoiding the "don'ts" which we usually ignore and when the consequences arrive we will not be surprised of the outcome. Pilot error occurs because of avoiding the safety measures before flying. Flying with undercharged transmitter or receiver batteries is considered pilot error because we are not careful of the consequences.

Also because we are not aware what to choose for a beginner aircraft, we buy the wrong type thinking that all airplane are the same. For a beginner, I would suggest choosing a high-wing, constant chord (straight wing) and tricycle type landing gear so that we can concentrate on the other controls. These features already have inherent stability as we have tackled before in previous chapters.

I remember when I was a teenager I bought an F16 fighter jet kit (propeller driven). I thought that it's only a toy airplane and I don't need any flying skills in order to fly it. I know how to build the plane by studying books and magazine on building model airplanes. But later I learned that I can't fly it because it is not a trainer aircraft. Then I bought another airplane kit, the piper cub. Yes it was a trainer on a full-size aircraft but I didn't realize that it is a scale model. I knew later that I couldn't fly scale model aircraft even though it was a trainer aircraft because it was "scale".

Why is it that a scaled trainer of a full-size aircraft is not recommended as a RC model trainer aircraft? The reason behind it is the aerodynamic characteristic of a full-size aircraft is different on a scaled down aircraft even if the model is exactly the same dimension from the original. The viscosity and size of air molecules cannot be scaled down for the model aircraft to behave like it's full-size counterpart. That is why when you scale down an aircraft that is very stable, the miniature will fly terrible. It is called "scale effect". The model has to be redesigned based on the lift and drag coefficients and Reynolds number on its miniature dimensions to achieve stability. On illustration of Fig. 22, the tiny circles represent the air molecules. On a full-size aircraft, the molecules are small compared with the scale model. For the model aircraft the air molecules are bigger so it will behave differently compared with the full-size aircraft.

Figure 22 : Full-size and model aircraft comparison

Materials are also a major consideration for a model aircraft. The secret for it to fly successfully is to build it light and strong. Traditionally, balsa wood was the first choice because of its strength to weight ratio and very easy to cut, sand or carve. Because the airframe is consisting mainly of balsa, repair was possible and easier unlike the plastic or foam materials. Other materials are combination of foam core wings covered with balsa skins, molded plastic fuselage and fiberglass fuselage. The covering for bare balsa frame is usually an iron-on plastic called "monokote". It is a strong mylar film coated with pigmented adhesive on one side.

Covering with monokote only need a handy iron to fasten the film to the airframe. After the plane is covered, just apply heat to shrink the film to remove the wrinkles and sags. It is far easier to apply than the traditional silk and dope. The combination of silk and dope provides added torsional strength but heavier compared with mylar film. It also needs an experienced and skillful builder because the total weight will depend on the hobbyist's skill and it should be built as light as possible.

Figure 23a : Typical model aircraft structure

Depending on the hobbyist's desire to enjoy this past time, some enjoys building as well as flying his or her model aircraft. Some love to fly but hates the tedious task of building. One thing in common for us hobbyist is that we love aircraft. We are in to this hobby to enjoy it so the best thing is to make all things simple. Sophistication most of the time will end to frustrations so the next time we plan to buy a model kit is to think ten times or more if this aircraft is suited to your skill. If we overestimated our skill, we will end up a closet full of broken airplanes.

Since flying skill is needed to enjoy this hobby, it is best to ask for help of an instructor. It is almost impossible to teach yourself if you are a beginner because it is important that your model will land in one piece. Take-off and landing is the most important maneuver to learn. Your model is safe whatever maneuver it makes as long as it will not touch the ground. Avoiding crashes is of utmost importance. When you have mastered take-off and landing, it is now possible to teach yourself any kind of maneuver you wish.

Flying a remote controlled model is very different from flying the real thing. Because in a real aircraft if you are in the cockpit, left is left and right is right. In a model aircraft, if your view is at the back, left is left and right is right. But when it is going towards you, then right is not right anymore. If you are not properly oriented confusion will result. Your right will become left and left will become right. Practice flying the airplane towards you because this is very helpful in case of dead stick landing.

Figure 24 : Comparison of aircraft orientation:
aircraft flying away vs. aircraft flying towards the pilot

Dead stick landing is when the aircraft losses it's power due to engine failure. Either the engine is not properly break-in or fuel exhaustion is the major cause of engine failure. The only available power is gravity where the aircraft glides until it reaches the ground. Control is very limited because you cannot climb again to make a perfect landing.

Some times there are other unexpected event that occurs when we are flying our model. The receiver some times experiences interference from other radio transmitter and may cause glitches to the servos. The effect is that the aircraft may suddenly stall and spin dive. The only solution to this problem is to apply opposite control input. When the airplane is spin diving to the right, apply left rudder control and elevator up to recover to a safe altitude. Practice on spin diving and recover in a safe altitude. Radio interference occurs most of the time in AM an FM band ( Amplitude and Frequency Modulation ) which are used in earlier version of radio controlled flying. Then came the PCM ( Pulse Code Modulation ) which replaced the AM anfd FM band which is immune to radio interference.

Today, there are many flight simulators available in the market, which is a very good way to start this hobby. This will orient you on flying "remote controlled". Flying in the cockpit is different from flying remotely piloted (see figure 24). And as the computer nowadays are getting faster and graphic cards available are like true to life, it is easy for us to master the skills of a true RC pilot. Mistake can be repeated because it is only software. Unlike in the earlier days, even the most stable RC aircraft can turn into an expensive litter with a very slight pilot error. The common flight simulators available in the market today consists of a transmitter box, cord, adapter and CD containing the software. All you have to do is to install the software, plug the transmitter adapter cord to the back of your computer's CPU casing (Either com1 or com2). Modern technology is a big factor in learning to fly so I think flight simulators is a very good place to start. There is a free flight simulator I'm using which I've downloaded in the internet. It is called the Flying Model Simulator or FMS. The astounding detail and realistic simulation is very good dispite of being a freeware. You can also add models which are available in the internet. For more info please just follow these links: Flying Model Simulator & RC airplane experiment studio page for FMS

So this ends up our short lesson in RC Airplane: Theories & Practice for Dodos and I hope this short lesson about radio controlled airplane helped you in my own little way. This is a very nice start before building and learnimg to fly your first airplane because you already gained knowledge in pre-flight lesson which is similar to full-size "ground schooling". Thank you for your time and patience in reading my article and enjoy flying!

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