Taking a look at radio controlled flying machines
We have all seen the various contraptions that have been created to enable man to fly. Some people tried making wings out of wood and paper and attached them to their arms and jumped off the roof of the barn, not successful. Man has been working on achieving flight in many ways for centuries. The early attempts were mostly unsuccessful. It is utterly amazing how advanced aircraft has become in the past few decades. The same is true for radio controlled model airplanes, as well.
Why then, do people keep coming up with unusual radio controlled flying machines. You can’t generalize them as airplanes because some don’t even resemble that which we perceive an airplane to be. In a recent post I had a link to a site that had a video of a flying lawn mower. It was about the size of a push type mower like the one you might use to mow your grass. It really flies.
I first saw one of these flying lawn mowers in a radio controlled modeling magazine in the late 1970′s. It was made out of foam sheets from the lumber yard, fitted with the radio control system and had a small nitro powered engine attached to the front. At about the same time someone came up with similar idea and created a flying iron (like you press clothes with). And, another magazine article was about a flying “Tin Lizzy” ( a model T Ford car). These things all flew and their owners had fun designing, building, and flying them.
One of the members of the local club where I learned to fly built a radio controlled model airplane out of cardboard boxes. It had a wingspan of about 8 feet and the length of the fuselage was about 6 feet. He designed it to look like a large sailplane or glider. It was made mostly from cardboard television antenna boxes. The engine was mounted on to strips of hardwood the extended out from the nose and it was controlled by a 3-channel radio system. If I recall correctly, the tail section was made out of balsa and covered with a heat shrinkable Mylar film. It wasn’t much to look at, but it was entertaining to watch and it provided a lot of fun and satisfaction for the modeler. One day he actually flew it from the club’s flying field about 6 miles to where I lived. He had someone drive his van and he rode in the back of the van with the side door open and he flew the plane as his friend drove the van along the side of the highway.
Modelers have come up with all sorts of flying machines such as flying disks, a broom with the witch attached, and even a doghouse with Snoopy sitting on top of it. Why do these people do that sort of thing? The technology has advanced to the point that we now have special remote controlled devices that are used in combat to reduce the exposure of our troops to enemy fire. There is a new age of miniaturization in R/C modeling that has created a whole new arena of tiny model helicopters, airplanes, cars, and even a real life sized dragonfly. I was watching a science channel on television recently an saw how a scientist discovered the mechanics of how a dragonfly flies. It was an amazing show that went all the way from research to a working full size radio controlled scale model of a dragonfly. They showed how well it can work for surveillance by hovering outside of some-one’s house and flew inside when the door was opened. Equipped with camera equipment this worked as an efficient spy.
Why do they do this sort of experimenting? Probably for a multitude of reasons but the first two that come to mind are to advance the technology and secondly to just have fun.
See you next time.
Tuning the radio controlled airplane engine
One area of learning the basics of flying radio controlled model airplanes that we have barely skimmed over up to this point is the tuning of the nitro powered model plane engine. This is a very important part of getting ready to fly. But, before you fly with a brand new engine, it should be properly “broken in”.
You will hear discussions on the “right” way to break in a new engine, but really there is no one way that is the best way. What is important is that you run the engine either on a test stand or mounted in the airplane until it starts easily and runs smoothly without excessive heat.
It is important that you select the proper fuel for the engine. You have choices of the type of lubrication that is in the fuel as well as the nitromethane (nitro) content. Model engine glow fuel can either contain castor oil or synthetic oil, or sometimes a combination of both. As far as the amount of nitro in the fuel is concerned, basically for your trainer 10% to 20% will give you adequate performance. Check with your hobby dealer or your instructor to find out what fuel is commonly used in your area.
Although you can successfully break in your engine while it is mounted in the airplane, there are a couple of reasons why I like to use a test stand for at least the first few tanks of fuel. When the rc model airplane engine is running, oil will be blown out of the exhaust and if you use a stand, you won’t have to clean the plane. Also, if your test stand is mounted at a comfortable work height, it will be easier to work with the adjustments and make needed repairs. Either way you need to run a few tankfuls of fuel through you engine at various operating speeds and fuel mixture settings.
The engine should be fitted with the proper size and pitch of propeller as recommended by the manufacturer, before starting the break in process. If you are going to leave the engine mounted in the plane, make sure that is well secured in place. Either use some type of hold down device or have a trusted individual hold the plane. While tuning and breaking in the engine, you will have to run it at varying speeds, so you will want the radio system turned on. Remember, if you are doing this at the flying field, you must be cleared to use the frequency that your transmitter is set up with. Also, if there are other people flying their models, you should be away from the flight line to help with the noise problem. These are some more reasons that I prefer to use a test stand at home for the break in.
With your test stand securely mounted to a table or a workbench, it is time to get the engine running and tuned. You will need a source of energy for the glow plug and some means of connecting it to the glow plug. We will go into setting up a flight or field box in a later post. Starting and running the engine has its own set of safety hazards. You will need sufficient room all around the test stand to allow you to keep away from the propeller and especially away from the ends of the prop. Tip: A black or other dark colored prop will be nearly invisible while it is spinning. To make it more visible, dip the ends in some white model airplane dope. Never stand in line with the propeller. If the prop is cracked or damaged in some way, at high speeds it could shatter and someone could be hurt. When the engine is running it is safest to stand behind the engine.
Any internal combustion engine needs three things to start and run. Air, fuel, and a source of ignition are all required in the right mixture to make the engine run properly.
Fill the fuel tank with fuel by disconnecting the fuel line from the carburetor and connecting a fuel bottle or pump to the fuel line that is connected to the tank. After the tank is full, reconnect the fuel line to the carburetor.
You need to make an initial adjustment to the needle valve setting before you start the engine. Check with the manufacturers instructions on the recommended inital setting. If you don’t have the instructions, it is common practice to gently screw the needle valve all the way clockwise until the needle contacts the seat. Be careful not turn it too tight, because you could damage the needle valve or the seat. Back off the needle valve two full turns. There is a mark on the knurled knob th help you count the turns.
Finally, we are at the point of starting the engine. It takes longer to explain how this done than it does to actually do it, so please bear with me. The engine has no fuel in it at this point and it will not be able to draw fuel from the tank without a little coaxing. Do not connect the battery to the glow plug just yet. If you are going to start the engine by hand, place you finger tightly on the carburetor’s air inlet port and turn the prop counterclockwise ( looking from the front) and watch the fuel line to see when the fuel reaches the carburetor. Don’t overdo this step because you can easily “flood” the engine and make it very difficult to start.
Now, it is time to connect the battery to the glow plug and start the engine. Open the throttle a little (you will quickly learn how much) to allow some air into the carburetor. Give the glow plug a few seconds to heat up and then using a “chicken stick” to keep you fingers off the prop, flip the prop smartly counterclockwise until the engine fires and begins running. At this point it will not be running smoothly. Slowly open the throttle and listen to the sound of the engine. It may take several attempts to get the engine to run through the full range of speed, but keep slowly turning the needle valve in until the engine breaks in to a full two-cycle sound when at full throttle. Then back it out about 1/8th to 1/4th turn and let run as rich as you can and still keep it running. At this point unhook the battery from the glow plur.
You have to be careful not to lean out the engine until it has had a tank or two of fuel run through it. The terms “rich” and “lean” refer to the ratio of fuel to air. A rich mixture is a high fuel to air mixture and a lean mixture is a low fuel to air mixture.
When you have it running on the rich side vary, the speed by changing the throttle setting. Don’t let it run at a constant speed too long at a time. The engine can “load” up with fuel if it runs too long at a slow speed and it could possibly develop excessive heat if you let it run wide open for too long while it is still brand new. Let the first tank of fuel run through the engine while varying the speed from slow (just above idle) to wide open at a very rich fuel mixture setting.
Watch the amount of fuel in the tank so that you don’t run it empty, because as the tank gets empty, the fuel mixture rapidly gets leaner and the speed will increase dramatically and that is not a good thing to do at this point. You should stop the fuel flow by pinching the fuel line between the tank and the carburetor with you thumb and finger thereby stopping the engine.
Le t the engine cool down slowly and repeat the fueling and starting process. This time and each successive time you should not change the initial needle valve setting. Run three or four tanks of fuel through the engine and each time you can work your way closer to getting it up to full two cycle, but do it slowly.
When you have completed the “breakin” process, reinstall the engine in the plane and be prepared to go through fine tuning when you start working with the instructor at the flying field. He will want to make sure that it is running properly so that you can benefit the most from your training.
I want to make this blog as informative and accurate as possible so as to provide the best possible instruction for beginning modelers. So, I welcome comments from beginners and experts alike. Thanks for your support and I’ll see you next time.
Working with your R/C flight instructor
All through this series of entries on getting started in flying radio controlled model airplanes, I have been emphasizing the benefits of having an experienced flight instructor’s help. You should be able to do a search on the AMA website for sanctioned flying clubs in your area and find a qualified instructor. You may also need to purchase a liability insurance, available from AMA. Some instructors are permitted to train new pilots and have them covered under their insurance for a period of 30 days. But, since AMA sanctioned clubs require members to have the insurance, you may as well get it right away.
The instructor will want to go over his and your responsibilities within your relationship. One thing is a verbal or written agreement on what happens in the event of an accident. The instructor will do everything possible to help you learn safely and as quickly as possible. However, you need to have the understanding that unexpected things do happen and he may not always be able to avoid disaster.
Before he will start your training, he will discuss the terms of your training and the rules that are in effect at their club. The instructor will work with you as long as you need assistance and he will advance you through your lessons as he sees how you are progressing.
Some instructors will use only your transmitter and the two of you will share it to fly the same airplane. This method can sometimes lead to problems in that the student will be reluctant to pass the transmitter to the instructor when asked to. The student may feel that he still has the plane under control and the instructor (having more experience) can see the plane getting into a situation that can quickly turn bad. This is one of the things that can cause the student to go looking for another instructor. It is imperative that the student trusts the instructor and respects his judgment. There is simply no room for argument when that model is heading for trouble. The students reluctance or hesitation in handing the control back to the instructor may not leave enough time for the instructor to regain control and prevent an accident.
Another method that allows the instructor to have total control of the model at all times is to use a training system (buddy box). This is to use two same brand transmitters connected by a cable. One transmitter will be the master and it is set up to send the signals to the receiver(this one is for the instructor) and the other one is just used for the joysticks( the student uses this one). The instructor will take control of the plane and get it airborne and after he has adjusted the trim controls for each function and has the plane set up for straight and level flight with throttle set at some point between full and 1/2 throttle, he will press and hold a button on his transmitter which gives control to the student. If the instructor sees the plane getting out of control he just releases the button and has immediate control until the plane is back on a straight and level path. Control of the airplane is passed back and forth until the instructor decides the student has advanced to the point where he is landing and taking off on his own and has demonstrated his ability to handle emergency situations.
Having a qualified instructor to train you and to keep you on the right path helps avoid costly and dangerous accidents. So check out the AMA, get your membership and insurance and their free magazine for one year. The AMA is a good place to get started with and they will even assign you some cool numbers to put on your models. Have fun and we will talk again next time. Please respond in the comments link with any questions or suggestions that you may have.
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