From Model Airplane News

(by Gerry Yarrish)


We've all been here, done that!
The life expectancy of your RC airplane is directly proportional to how well you follow directions. That is to say, you've built and setup your plane properly as explained by the instructions. This article is intended to give the first time model builders some helpful tips for being successful the first time out. We’ll talk about avoiding the avoidable, not correcting for things like crosswinds or hitting something with your plane.
There are several things that are common in that they can greatly affect your airplane’s safety. Like a weak link in a length of chain, any one of these things can bring the best built planes down. Let’s break down these areas of concern into the following groups.
Center of Gravity Balance Point. In my opinion, more airplanes are damaged or destroyed on their first flight because they were improperly balanced. The balance point for all RC model airplanes (with the exception of small foamy RTF planes,) are called out on the plans of a kit built plane, or in the instructions of an ARF plane. It is absolutely imperative that you take the time to balance your plane properly. Use a balancing jig or simply use your finger tips to hold the plane by the wing to see where it balances. If the tail hangs low while placing your fingers where the instructions say the balance point is, it is tail heavy. If the nose hangs low, it is nose heavy. Of the two, slightly nose heavy is better than slightly tail heavy. As the plane becomes more and more tail heavy, the more and more sensitive it becomes to control inputs until it gets to a point where it is uncontrollable. We’ see this all the time. The plane takes off and the wing rock back and forth. The nose stays high and eventually the plane snaps to one side and crashes. You prevent this by adding nose weight.
   

Engine/Fuel System. The next item most likely to kill your plane is an unreliable engine. This can be caused by a poorly broken in engine, an improperly adjusted carburetor and/or an improperly installed fuel tank. Always follow directions and break in your new 2-stroke or 4-stroke engine before trying to fly. This requires several tanks of fuel and a controlled running of the engine to condition it for proper operation. What you want to do is obtain a reliable idle and a smooth transition from idle to full power. When it comes to power output, always run the engine slightly rich, not lean. Lean engine runs cause overheating and can lead to a damaged engine. The fuel tank should also be installed properly to supply the engine with fuel. Assemble it correctly and install it so the center of the fuel tank is even or slightly below the center of the carburetor. The simplest setup is a 2-line setup with the output line attached to the carburetor and the other line acting as a vent. You fuel the tank by removing the line from the carburetor. A common problem is a fuel clunk that gets jammed forward in the fuel tank after a hard landing or nose over. Always make sure the fuel pickup line is free to move around in the tank. If it is jammed forward, the next time you take off and the model’s nose is pointed up, the fuel level will move back and the clunk will start to suck air and cause your engine to lean out and die.

The model airplane engine is an important investment in your hobby. Treat it right and it will treat you and your airplane right.


Radio Battery. Another common failure point is the onboard battery powering the receiver. You should always fully change your radio system the night before you go flying and have a battery checker to monitor the condition of your battery pack at the flying field. Batteries seldom fail before you next flight, and when they give up the ghost during a flight, you are out of luck because your model is going to lose control and it will eventually hit the ground…hard! I check the battery voltage before every flight with a loaded volt meter. You simply plug it into the charging jack and it tells you what the voltage levels are. If the voltage is below 4.8v for a 4 cell pack or below 6v for a 5 cell Ni-Cd pack, do not fly! So it is always good to have a DC quick charger/peak detection charger in your field box so you can top off your battery pack. Also, check the battery switch and connections. Never install a battery pack without foam rubber padding. Always make sure your pack is securely installed and doesn't more around.

 Use good quality battery packs and use high capacity packs when you use more and more servos in a plane.


Final Condition Check Besides these three basic failure points, always check the condition of your model before every flight. Make sure the radio system and servos are properly installed and working correctly. If you have a programmable radio, make sure you have the correct model memory called up for your airplane. Check the screws and clevises and make sure everything is connected and secured properly. If you have recently repaired a plane, or if it is the very first time you've brought it to the field, have a friend go over it as well. A second pair of eyes can often detect something you over looked. Always check your control throws for proper amount and proper direction.


Don’t push a bad situation! Again, we see this all the time! If your engine is just not operating properly, or if something is not working correctly, just don’t fly! The best course of action is to step back and take a breath. Maybe you need to work on the engine back home on a plane stand, to solve the problem. If an aileron is twitching, maybe the servo needs to be replaced. You are the pilot in command. Abort your flight attempt. The plane you save may be your own!