Getting Started Guide to Electric RC Flying
by Scottwired
Intro:
Updated 2/25/09 to add LiFe04 info. After a year of experimentation on my own on learning to fly Electric RC airplanes, I thought I would put together a guide so others could benefit and maybe not waste as much time and money as I did. If you follow my steps you will avoid many of the pitfalls that I went through. Don’t take everything here I say as Gospel, but use it as a guide when talking to others, researching web sites, looking at catalogs and visiting stores.
Please be aware that modeling may present hazards to participants and spectators. While every attempt has been made to convey accurate information, you alone are responsible for all current or future liability for personal injury, property damage, or wrongful death caused by negligence or application of information presented in this guide.
One topic that I am sure is at the top of your mind unless you are independently wealthy, how much is this sport going to cost? The answer is depends on what paths you take. You can buy a low cost 27MHz foam package for $150 and be in the air in a couple of hours. I would recommend against this path. The barriers to success are many, and you will probably end up frustrated with a bunch of broken foam pieces.
Instead what I would recommend is the following steps. You will end up spending about $600 in stages, but you will avoid most of the barriers to successful flight, and have some good equipment to expand upon. If you are a good shopper, scratch builder, or if you pick up some old equipment at a swap meet, you can spend less. If you have a quality setup, you will crash less often, less severe and most times be able to repair the plane with some extra balsa or foam and glue. Even if you total the plane, all the expensive stuff will usually survive a crash, and the most you are out is dollars to buy another airframe, starting at about $50. I also have some pointers in the FAQ if you need help justifying the expense to your spouse or parent.
Another alternative is to start with Free Flight planes. These can be purchased as full kits or ARF. Free Flight is just that, you wind up the rubber band, or turn on a motor, and send it flying. There are actually clubs and competitions that specialize in free flight. Best part is you can get a kit for $20 and having the fun of spending several weeks creating your masterpiece. The cost per hour, when you consider the joy of building is pretty darn low, of course assuming you find building fun…
1) Start an RC Plane 3 ring binder
I have a notebook where I keep all my RC related manuals and articles. I would recommend you do the same. As you get a manual for a plane, charger, battery, radio, punch holes in it, and add it to your binder. Keep this binder with your flying equipment so when you need programming or setup information its readily available, and you are not tempted to guess.
2) Learn flight basics:
- This is from wings over Kansas site with some minor modifications, link included below.
WHAT ARE THE BASICS OF FLIGHT?
Flight may seem complicated, but in fact it's based on some simple laws of nature.
The
principle of lift
When you examine a cross-section of an airplane's wing, or airfoil, you'll notice that the top part is curved and the bottom part is relatively flat. This special shape creates lift, which makes the airplane fly.
The basic principle is as the wing moves forward, the air flowing over the top travels faster than the air flowing beneath, resulting in a lower pressure area above the wing. The relative pressure differential provides the upward force called lift. Lift is basic to flying. You say but wait, I have seen planes fly upside down, or 3D planes that have flat wings with no airfoil shape. How do they fly? There is an area of low pressure being generated above the wing. It’s just being created by the wing orientation or prop wash.
Lift
and gravity
In order for an
airplane to climb, lift must be greater than gravity, the force that holds
objects on the earth.
For an airplane to maintain level flight at a particular altitude, lift and gravity must be the same, or in equilibrium. When gravity is greater than lift, the airplane will descend.
Thrust and drag
As an airplane moves forward, the wing produces lift. The force of forward movement is called thrust, and it's created by the engine-driven propeller.
Like the wing, the propeller is also an airfoil. As it rotates, it creates "lift" in a forward direction that is called thrust. Thrust overcomes drag (resistance of an object toward movement).
When thrust is greater than drag, the airplane's speed increases. When thrust and drag are equal, the airplane maintains the same speed. Whenever drag is greater than thrust, the plane slows down.
Lift, gravity, thrust, and drag are the four forces acting upon the airplane.
The
parts of an airplane
An airplane, of course, is more than a wing, a propeller, and an engine.
The body of the airplane, which holds the motor, electronics, battery, fuel is called the fuselage
The tail of the airplane is called the empennage, and it consists of the horizontal and vertical surfaces called the elevator and rudder. They help keep the plane traveling straight and level.
Parts of the wing, horizontal stabilizer, and vertical stabilizer are moveable to provide the pilot with the means to control the airplane. These control surfaces are called ailerons on the wings, elevators on the horizontal stabilizer, and rudder on the vertical stabilizer.
Control
As the pilot, you control the airplane, and determine how it flies. The different movements of your controls will cause corresponding movements in the airplane. Here are some basic airplane movements.
Pulling the right stick towards you raises the elevator, which in turn forces the tail down and the nose up. This serves to create more lift than gravity and the airplane will climb, as long as there is sufficient airspeed. If there is not sufficient airspeed the plane wire stall and nose over. To help produce the extra lift needed in the climb, you usually need additional power from the engine, which you achieve by using the throttle control. Pushing the right stick away from you lowers the elevator, forcing the tail up and the nose down. This reduces the lift, and gravity makes you descend.
The left stick controls the movement of the plane from right to left in much the same way as the rudder of a boat. Pushing the left stick right forces the nose of the airplane to the right, and moving the stick left produces the same movement to the left.
Moving the right stick moves the ailerons in opposite directions, enabling you to raise or lower either the right or left wing which enables the airplane to turn faster than using rudder only.
To change the attitude of the airplane, its relationship to the horizon, you simply use the control surfaces and the power of the airplane. It's an exercise in coordination. As a beginner you can control the attitude of the plane quit well using just the right stick to operate the elevator up/down direction, and ailerons left/right direction. Rudder is used more in takeoff/landing and more complex moves.
Here are few links to look at:
http://library.thinkquest.org/3720/toc.htm
http://www.wingsoverkansas.com/learn/article.asp?id=256
3) Network with other flyers:
Visit an RC field and talk with the guys that are there. Where is the closet RC field? AMA has a search function that will give you location and contact info for a field close to you at http://www.modelaircraft.org/clubsearch.aspx Most people will be happy to strike up a conversation and tell you what they have learned over the years. Be prepared for different opinions, passions, on topics such as radios, equipment, gas or electric. Read articles from manufactures and on newsgroups. Meet the instructors at the field and ask them what plane/equipment they would recommend to work with.
Visit a local RC store and ask them where people fly in the area. You can go to any of the following manufacturer’s links such as Horizon or Great Planes and find a local store. Also try to make some of your major purchases at the local store and help keep them in business. You will want to help keep a local business solvent so you can stop by ask questions, and buy things you may need right away like a servo or prop.
Also there are many great sites on the Internet, loaded with info, here is a sampling of my favorites:
http://www.rcgroups.com/forums/index.php -- First Place to go besides visiting an RC field. It’s a great source of information, and place to ask questions. Look at the beginner’s area for helpful hints.
http://www.3dhobbyshop.com/default.aspx -- Good store with lots of helpful info. Great technical support. Also if your travels take you to Fredricksburg, TX make sure to call them and stop by. They have a great group of guys to go fly with, and they will be happy to help you set up a plane and get you started in flying.
http://www.horizonhobby.com/Articles/Article.aspx?ArticleId=1647 -- beginner’s guide. Horizon makes some good equipment including the Spectrum radios, my recommendation for a park flyer, even AMA endorses them as the future of RC flying.
http://www.easyrc.com/ -- Tower hobby’s beginner guide.
http://www.greatplanes.com/ -- Great site, good setup and configuration info.
http://www.hobbycity.com/hobbycity/store/uh_index.asp -- Low prices on servos, ESC, Motors, props, LiPos.
4) Flight Simulator:
Buy a Simulator program that uses a RC remote type of controller. I didn’t do this until 9 months into trying to learn. Big mistake. There are a couple of good programs such as FS One http://www.fsone.com/ and Real flight G3 http://www.realflight.com/ Its worth the investment, in saving time/frustration of ramping up the learning curve, and last I checked, crashing simulated planes is much less expensive than real ones. Spend a few weeks working with the tutorials until you can take off, fly and land (hardest part), several times in a row without crashing. As you get better add variables in such as cross/variable winds to increase your skill level. Any time you have difficulty flying a particular move on a real plane, try the same move repeatedly on the simulator until you master it, and it becomes second nature, especially if it caused a crash.
5) Join AMA http://www.modelaircraft.org/
AMA has a really good magazine. It has great articles on safety, construction, advertisements, RC meets, and the world of RC modeling. They also provide liability insurance when you fly at an AMA sanctioned field and promote interests/rights of RC modelers. Also you need AMA membership before you fly at any sanctioned club field.
Next you need to buy a plane, radio and accessories. This is one of the fun parts, but encompasses lots of decisions. Let me hit the major ones:
6> Gas vs. Electric Decision:
There are people that will debate this and be very passionate for one or the other. I don’t think one is better than the other anymore than a fork is better than a spoon. Depends what your criterion is. I will distill a few of the points that you need to consider, which will hopefully help your decision.
- Noise: Gas engines are typically noisier than electric, which makes for a more realistic experience, but bad if you are trying to fly somewhere besides an RC field and don’t want to disturb other people around you. This is also a consideration when building and testing the plane at home.
- Cost: For small planes electric is most cost effective solution, for large planes gas/glow is the way to go. At what weight does cost advantage switch from electric to gas? Goes up every year. I just bought a 5lb plane and decided on electric configuration, and I spent $150 more than a gas configuration. By the time you figure fuel costs over the life of the setup compared to the upfront for batteries, it’s about a wash. To me it was worth it to be able to leverage batteries and chargers from my other planes. Batteries are a big up front expense, but as long as they are cared for properly they will last a long time in the 100-200 cycle range. Gas/glow engines require expensive fuel, every time you fly.
- Fuss: Electric motors are in general easier to work with. Charge the batteries, run your checklist and go. No engine adjustment, smelly gas, exhaust, or post flight cleaning to mess with. Note that some people consider this fun, like changing your own oil, brakes or tuning up the car.
- My conclusion? Start with Electric. You can fly an electric plane anywhere there is a 300x300ft field with no people or trees on it. This gives you more options to fly, which means you will get to fly more often. Some guys will carry a park flyer in their trunk and stop by a small field on the way to or from work and get a 15 minute flight in. This is not an option for most glow/gas flyers.
7> Plane Size:
What size plane should a beginner start with? Just like a boat in a choppy lake, a bigger/heavier plane will be easier to handle in higher wind. So assuming you are outside, I would recommend something at least in the 18-24oz size with light wing loading. You will want to limit yourself to under 3mph wind days until you get more experience, no matter what size plane you have. If you are flying a slow stick type of plane, go with no wind.
8> Plane Type:
I prefer a high wing trainer type of plane for a starter. Some people like the prop behind the wing for a beginner plane, but in my experience, they don’t seem to survive crashes any better. Look for something that is advertised as a beginner plane or trainer. If you look at a picture of it, the wings will have a pronounced dihedral, where the wing is slanted up, not a straight and flat. A Dihedral adds stability since it tends to keep the plane level, which is a good thing for a beginner. Sport and 3D planes typically have no dihedral. This makes it easier to do aerobatic tricks such as rolls. Don’t get a 3D plane, or a sport flyer, they are very responsive and hard for a beginner to fly. You want something that is slow and forgiving. You may also want to limit your first plane to one without ailerons (the surfaces that move on the back edge of the wing), and stick with a plane that uses the rudder and elevator only. I actually found planes with ailerons easier to fly, as long as you limit the travel of all your control surfaces, concentrate on keeping the plane level, and have an instructor get it off the ground, trimmed and can land it for you for the first couple of flights.
The other variable you will see is RTF (ready to fly), and ARF (almost ready to fly). Full kits where you have to actually build the wings, fuselage, etc are pretty hard to find. The choice between RTF and ARF is not critical. Ones guy’s definition of an ARF can be different from another, anywhere from assemble in an evening to 3-4 evenings of work. ARF is usually a little cheaper, mainly because it’s cheaper to ship the plane in 10 pieces instead of having a bigger box for the plane completely assembled.
Once you pick a plane, assuming you are going electric, you then have to decide on motor, prop, and ESC. Best bet for an electric motor is a brushless outrunner. Most store sites will have a recommended motor, prop and ESC that matches the plane. This is certainly the easiest way to make sure you have the correct equipment. I would still run the calculations on how to select the right configuration section. At minimum you should measure the current with a power meter in series with your battery at full throttle and make sure you are within continuous current specs for the ESC and battery, and max power specs for the motor. See motor system selection below for more details.
I also recommend concentrating your learning experience on one plane at a time. Master flying that plane well before trying fly another one. Otherwise you may confuse characteristics of one plane with another and crash, especially when first starting out.
9> Construction Material:
I personally prefer balsa and plywood planes. They are fairly stiff, predictable and seem to tolerate a crash better than a foamy. When I say tolerate, it means for more cases than with foam, the plane is repairable. I have tried to repair lightweight cut foam planes without much success. Note that this is just my preference based on how well different planes survive or are repairable for another flight, and still fly predictably.
There are lots of great materials out there to make a plane out of. Dapron, EPS, Balsa and others I haven’t played with yet. I watched a guy called the mad scientist in Fredericksburg fly planes made out of blue foam from the building supply store. His planes were built in all sizes, usually with a yardstick as a spare in the wing, the rest of the plane assembled from blue foam, hot glue and a heat gun to help bend the material. He flew several models, doing all sorts of 3D moves, and flying in high winds!
Just make sure whatever plane you choose is easily repairable, since you will crash it at some point. Note that some crashes aren’t worth a repair. I try to limit my repairs to small dings like motor mounts, landing gear coming loose, cracked fuselage or wing. If you have to rebuild an entire section of a plane, best to start with a new one and move all the electronics over. I think this is one of the fun things about RC flight. You can push the performance envelope and try stuff that you would most likely end up dead if you were flying a real plane, and the most you are out is $50 to buy a new ARF.
10> Radio Technology:
There are two parts to a radio system, the transmitter, what you hold in your hand with the joysticks and buttons on it, and the receiver, which resides in the plane. Servos and an ESC plug into the receiver; these are what actually move the controller surfaces on the plane. When you move the joystick on the transmitter, the control signal being transmitted by your transmitter to the receiver changes, which changes it signal to the servo, and the control surface moves. The transmitter has its own battery pack, which you need to make sure is sufficiently charged when you start. The receiver will also have a battery pack, but in the case for most electrics, shares the motor battery pack, if the ESC (electronic speed control) has a BEC(battery eliminator circuit). Most ESCs have a BEC, to the point that it’s typically only mentioned if it’s not included. The BEC is a voltage regulator the outputs the correct voltage typically 5V for the receiver power. The power is driven back from the ESC to the receiver on the ESC control cable.
Many of the starter kits come bundled with a 27MHz radio. I would recommend skipping over this technology. This is a controlled band that includes RC cars. You could fly ok one day and crash the next because some kid around the corner turned on his RC car or plane, and your plane goes spinning into the ground.
The workhorse of the industry is 72MHz radios. You can find lots of quality, reasonably priced transmitters on the market. Used correctly these are a great choice. However, note that you need to make sure you don’t turn your radio on if someone else is already using your channel or within 3 miles of an AMA sanctioned field. That is why all the RC fields have a big board with a list of channel numbers on it. Only one person can have a radio on a particular channel at a time. Note if you violate this rule, turn on your radio and cause someone else’s plane to crash, then you are expected to pay for the other person’s plane. This can get quite expensive since some planes cost $1000s. Also planes or helicopters that are out of control have the potential to hit and injure or kill someone. Again, this is never an issue if you follow the rules at the field you are on, buts its one more thing you need to think about if you use 72MHz radios.
Note: AMA National Model Aircraft Safety Code dictates that you will not operate your 72MHz radio within 3 miles of a sanctioned RC field to eliminate RF interference and potential of you crashing your airplane or another flyer’s airplane at the flying field.
Latest technology and what I use is spread spectrum 2.4GHz. Just introduced in 2003, they are taking the industry by storm. There is no need to worry about interference with other radios or what channel you are on. You also have the peace of mind when flying at a local non RC field that other devices or another radio will not cause you to crash. You can find spread spectrum radios from Horizon hobby http://www.hobbyzone.com/rc_parts_transmitter_spektrum_dx6.htm. The DX6 is for park flyers only, the DX7 will work with any size of plane.
If you are working with an instructor, which is highly recommended, make sure your radio trainer jack is compatible with their transmitter equipment. Note that JR and Spectrum radios are compatible for training. When your transmitter and the instructor’s transmitter are connected with a training cable, the instructor’s transmitter has control of the plane except when he/she pushes the trainer button. When the trainer button is depressed, your transmitter then controls the plane. This way the instructor can take immediate control of the plane at the first sign of trouble. This is much more effective than passing the transmitter back and forth, and will save you from many crashes.
11a> Electric Motor System Selection
There are 4 main pieces you need to be concerned about in an electric motor system, Motor Prop, ESC and Battery. All need to be appropriately matched and designed as a system or your plane will be under powered, over powered, or you will damage some of the components. When you buy a plane the manufacturer will suggest a combo of these components. This is a good place to start, but you can probably save some money, and put together a better performing system on your own. At minimum you should verify the power at full throttle is within recommend current and power guidelines for each of the components using an inline power meter once you have the motor and prop installed in the plane. These are available at any hobby store retail or online.
The Motor:
There are three main types of electric motors that you will come across. Brushed, inrunner brushless, and outrunner brushless. Note that you need to match up the correct type of ESC for a brushed or brushless motor. Fortunately this is easy since the brushed has two power leads, and brushless has three and always calls out brushless in the packaging/ordering info. If you are buying a motor, get a brushless outrunner. They are not that much more expensive and have superior performance characteristics for most applications since no gear box is needed. I also find the gearbox one of the weakest links in the system when I crash.
Motor Size:
Most motors will come with a power rating. As the throttle is increased the power output of the prop goes up. Most ESC are not changing the voltage going from the motor to the battery, but are controlling the % of the time that the voltage is applied to the motor. At full throttle the voltage is on all the time, low throttle the voltage is off all the time and at half throttle the voltage is applied 50% of the time. As the throttle is moved up, the % of on time increases. Motors will have a max voltage and current spec, these should not be exceeded when designing your power system.
Prop:
A Prop must be properly sized for a given plane and electrical system. Fortunately most planes or motors will give a recommended prop(s) to use. There are two main variables on props the length and distance traveled in one revolution in the blade was cutting through an imaginary solid material. So a 12x7 prop would cut a 12 inch wide hole through the air and travel 7 inches forward in one revolution. All else being equal, a larger or shallow prop will make the plane fly slower. A small deeper prop will make the plane go faster. Of course this is an oversimplification, but you get the general trend. The other factor to consider on prop is what RPM the motor will turn for a given loading. Fortunately you don’t have to worry too much about RPM unless you are lightly loading the motor. Most outrunner setups are designed for lower RPM, so you don’t have to worry about a prop disintegrating.
ESC (Electric Speed Control):
Most ESCs are actually two devices in one; the motor speed control, and battery eliminator circuit, which powers the receiver radio and servos. Like the motor you need to pay attention to the rated voltage and current handling capability. Don’t exceed these. Often the ESC manufactures will make it even easier for you and specify number of LiPo or NiMh cells it can safely be driven by. There are three sets of wires coming from the ESC. The black and red power leads, these need to be soldered to a male dean’s connector for the battery. Then there is a small gauge 3 wire cable with a plug on it that goes to the throttle control of the radio receiver. The third set of leads goes to the motor, 2 if brushed, 3 if brushless. Don’t worry about the order, just reverse two of them if the prop spins in the wrong direction when you power they system up.
Battery:
There are three main technologies used in RC planes. NiCd/NiMh, Lithium Polymer, and Lithium Iron Phospate. Most RC planes are now powered by Li-Po due to its superior power to weight ratio.
Batteries are one of the most expensive parts of the plane, especially if you don’t treat the batteries correctly, they will be damaged with a shortened life span, or could explode, but this is rare. There are a couple of things to pay attention to on a battery.
Capacity: This is specified in mA/Hours. A 1000mAHr battery will run for 15 min with a 4Amp load.
Voltage or # of cells: Most are 11.1V or 3 cells, but can range from 2-10 cells.
Continuous discharge current: usually specified in XC where X is typically 15 or 20, and C represents the capacity of the battery. So a 20C 1000mAHr battery can be safely run at up to 20A discharge rate. A good rule of thumb is to keep the average discharge rate below 12C for lower cell temperature and longer cell life. So you are better off designing a system to run on more cells at a lower discharge rate then fewer cells at a higher discharge rate to get the same amount of power. Note that the Motor, ESC and BEC need to be rated for the max voltage of the battery pack you select.
Battery Packs can be connected in series for a higher total voltage output, or in parallel for higher current/capacity. Make sure to only do this with same capacity packs in series, and same # of cells for parallel configurations.
Lithium Polymer batteries require a special type of charger, make sure to buy a lithium compatible charger and use it in the correct mode. Lithium Polymer batteries will explode and burn when charged or handled wrong. They have burned houses down. For them to be modified by an amateur is dangerous. Don’t charge a Lithium Battery indoors. Place the battery in a fireproof container while charging. Always observe the cell while charging. If it starts to heat up, swell, discontinue charging immediately. Do not exceed max discharge current for a battery. All of these conditions are a precursor for an explosion or fire. Read all the safety instructions that are provided with your charger and battery.
Almost all batteries come with a cell balancing connector. Balance your batteries often, preferably every time you charge. Unfortunately every battery manufacturer seems to want to have a custom balancer connector. Either stick with one brand of battery, or get adaptors cables to match a common balancer connector that is compatible with your charger. I also use a female dean connector on the power leads of the battery. AMA recommends against an amateur from modifying any battery pack. If you are experienced with a soldering iron and still choose to modify a battery pack, be careful when soldering or cutting leads on any battery. Only modify/expose one lead at a time, otherwise you have a good chance of short out one of the cells. This could lead to an explosion, fire, bodily harm, battery damage or all the above.
Lithium Iron Phosphate:
LiFe04 is an alternative battery technology to consider over LiPo. While the power density is not as high as LiPo, it has many attributes that make it superior to LiPo, at least for sport flying.
Advantages:
1> long term stability. LiPo batteries sitting at room temperature not being used will lose about 10% of their capacity in a years time. They can be stored in the refigerator (not freezer) at half charge to slow the degradation. LiFeO4 don’t degrade significantly over time.
2> Charging: LiPo batteries should only be charged when cool, and at 1C rate. Violating these conditions will shorten # of useful charge/discharge cycles and reduce the high discharge current capability (C rating) of the battery. A 20C pack will quickly fall off to 5C capability or less. LiPoFe batteries can be charged a 3C rate or higher depending on manufacturer and charger, although high charge rates may reduce total # of charge/discharge cycles the pack is capable of.
3> Handling: If you handle a LiPo when it’s hot, you can create salt deposits in the cell, which you guessed it, reduces the C rating and capacity of the cell. Since LiFeO4 are in a metal can there are no handling issues.
4> LiFEO4 batteries maintain high discharge rates through entire discharge cycle. 18A for the 1200mAHr cells, 40A+ for the 2500mAHr cells. LiPo’s max discharge rates fall off quickly, especially when they are not handled correctly.
5> LeFeO4 cells will often last for over a 1000 charge/discharge cycles. I have had LiPo cells become unusable after 50 cycles.
6> LiFeO4 will vent when subjected to over voltage or over current conditions, but typically do not explode into a fireball like LiPo cells when subjected to these same conditions. The cell will still be destroyed, but at least you didn’t start a fire.
Disadvantages:
1> LiFeO4 have lower power density, and lower voltage per cell. It will typically take a 4 cell pack to equal same voltage as a 3 cell LiPo pack, and it will be heavier.
2> LiFeO4 are more expensive to purchase, with fewer choices of manufacturers.
3> Limited charger options. FMA direct makes chargers capable of LiFeO4 (A123), and a few others, but you really have to look for them
4> Some ESC are not compatible. LiFeO4 cells need a cutoff voltage of 2.0-2.4V/cell, LiPo cells need a cutoff at 3V/cell. You will need a programmable ESC that you can set the appropriate lower cutoff voltage. If it’s too high the Motor will not run or cut off soon after takeoff. If the cut point is too low <2V/cell then you will damage the pack.
Battery Care:
Li-Po Batteries are good for 100-200+ cycles if they are used properly. Never discharge to less than 3V/cell, overcharge or run at a higher than rated charge/discharge rate, overcharging past 4.2V/cell, or store at high temp or freezing. If you leave your plane in the car during work, best to take the battery with you. Some manufactures also recommend storing at 50% charge. Each battery in a Li-Po pack is matched for capacity and discharge rates, but there are some variations. If you don’t use a balancer, the variations in charge/discharge rates will accumulate over time and soon one battery in the pack will either get overcharged or over discharged, ruining the pack. See the RC groups for lots of discussions on batteries or http://www.fmadirect.com/. FMA Direct seem to have the most universal charging system I have seen so far, with adaptors for most common Li-Po Batteries. They even have a discharge monitoring circuit, which is good for preventing over discharging of any cell in a pack.
Configuring:
So now that you understand the major components of the power system, how do you pick a set for your plane? It’s actually not that hard. The below table is a good rule of thumb to sizing the system:
75-100 Watts Per Pound for a Trainer & Sport Performance
100-150 Watts Per Pound Aerobatic & High Speed Performance
Over 150 Watts Per Pound 3D & Extreme Performance
So a 150-200W power system will be appropriately sized for an up to 2lb (32oz) trainer. If you under power a system, the plane will not take off, act sluggish or crash. If you over power it, it will run really fast and be hard to handle. Don’t forget to include the weight of the motor, electronics and battery as part of the planes total weight.
So once you have a power target, pick a battery, ESC and motor that can handle your targeted power level. I would actually recommend at least 20% margin above your targeted max power level for better component life. Most power system are setup for 3 cell Li-Po, so for our above example at 200W, with a 3 cell li-po battery the motor will be pulling about 18A. Note this is an approximation, as the battery discharges, or is put under heavy load, the battery voltage will go down, and since power=volts*amps, the power will go down as well. So a 20C 1000mA/Hr battery would be barely sufficient to handle this load 18A vs.its 20A rating. Probably not a good idea for 2 reasons, first you will be running the battery near its rated capacity which will shorten its life. Second it will only run for 1/18 of an hour at full throttle, or only about 3 minutes. Not much time to have fun. Something in the 2400mA/Hr range would be more appropriate. Same sized Li-Po batteries can be connected parallel or series as well to meet a desired power output. As a general rule of thumb if the current is exceeding 30A, check to see if you can pick a different motor and ESC that will run at a higher voltage by using 2 battery packs in parallel. At higher currents the battery, cable and ESC internal resistance start to become significant, cause more power to be consumed in these components and less by the motor.
Important: Once you assemble the plane and install the motor, prop, battery and esc connect a power meter in series with the battery. Run the throttle up and check the current draw and make sure it is within the battery, esc and motors max current. If not, switch to a smaller or shallower prop.
11b> Gas motor selection
I can’t add much here if you want to go this route since I fly electric only. You might look at the Learn to Fly section of the ARCA web site.
12> Servo Selection:
A servo is a motor that is attached to a position feedback device. Generally there is a circuit that allows the motor to be commanded to go to a specified position. In RC planes the servo moves the control surface based on a signal from the radio receiver, and is powered by the ESC or 2nd battery through the receiver. There is usually 1 per control surface, rudder, elevator, each wing aileron, and one for the throttle if you are running gas. The wing ailerons servos share a common control signal and power using a Y cable. Sometimes only 1 aileron servo is required with linkage that connects to opposing arms off the servo. There are different sizes so make sure you buy the correct size to fit your plane. Most common are standard and submicro. You can buy cheap or expensive servos. Cheap ones will do the job for a beginner, but note that they will wear out quicker than an expensive servo with metal gears and ball bearings. The other main delta in servos is torque rating and response time. As a beginner you want a slower, lower torque servo, which will be more forgiving and smooth out some of your random excess control movement. Listen to the servos when you power up the plane. Once they initialize if you can hear them buzzing, then you either have some binding in the linkage, or the servo is under powered for the application. I would recommend fixing this issue before you fly, otherwise a servo could fail, causing your plane to crash. The servo has three wires, the black or brown wire is the minus- connection. Don’t plug the server connector in backwards, you will damage the server, receiver radio or both.
For more details see: http://www.cs.wisc.edu/~bolo/shipyard/servos101.html
13> Building Checklist:
Supplies: Plane, Motor, ESC, Battery, Radio Receiver, servos (2-4 depending on plane), hobby knife, CA or hot glue (depends on what manufacturer recommends), screw drivers.
Take your time and follow the directions, check out RC groups or ask a friend if you don’t understand a step. Don’t use any damaged or cracked components, take it back to the store if it’s defective, most will happily replace it. Use a little glue as possible to get the job done. As you pour more CA on, it just runs down the side of the plane and then your fingers stick to the plane.
14> Initial setup:
Once you have built the plane, its time to do initial setup. Always be careful around the prop. I usually don’t even install the prop or connect the power to the motor until after I have done all the alignment, so I don’t have to worry about hitting the throttle and getting cut by the blade.
Control Surface Alignment:
Follow the directions for setting initial positions for the control surfaces. You will want the transmitter and receiver radios power, and the servo connected to the receiver. Make sure the sub alignment and trims on your remote are at zero neutral settings before starting. Sub micro tuning can be used to fine tune once you get it close by eye. The trims are used to make adjustments when in the air so make sure these are at center now so you have max adjustment flexibility when flying. Note that remotes typically support multiple models for the configuration setting, so make sure you pay attention to which memory/model number you are configuring and only use it with that plane if you do any customizing. If the servos are stalling or buzzing, resolve the binding issue. Disconnect the control linkage from the servo and figure out why it’s binding. The control surface should move freely and easily when it’s not connected to the servo.
Servo Direction:
Check the direction the flaps move when you move the stick on your radio. Also make sure you have the correct servo connected into the correct position on the receiver. When you pull down on the right stick, the elevator should go up. When you move the right stick to the right, the starboard (right when viewing from the back) aileron should move up, and port aileron (left from the back) should go down. When you move the left stick to the right, the rudder should go to starboard (right when viewing from back). If they move the wrong control surface, or don’t move anything, check the connection to the radio. If they move in the wrong direction reverse the corresponding servo direction in your transmitter setup, see the transmitter manual on how to do this.
Control Servo movement and exponential:
For first flight I would recommend limiting the servo travel and turn on some exponential, especially for a plane with large control surfaces. Limiting the travel will make the plane less responsive and give you time to correct from wrong moves. Exponential travel dampens the control surface movement around stick center. This will also make the plane easier to control with less radical changes of direction with small stick movements.
Motor Prop and Power:
Next check the motor/prop combo. Never allow spectators or other flyers to stand in front of, or to the side of a moving prop. If someone moves into this zone, shut the motor down Make sure the prop pushes are back across the plane when you move the throttle. If not, switch any two of the wires coming from the ESC to the motor. After you ramp up the prop make sure it’s on tight, and spins without causing the plane to vibrate. If it vibrates or wobbles fix the issue before going on. Could be bad prop, prop shaft hole not center, or bent motor shaft. Always tie down the plane and stand behind the prop, not in front or on the side of it. Especially first time you power it up. The prop can cut down to the bone if it contacts you. Bigger props can severe appendages. Plug an inline power meter between the battery and ESC. Ramp up the motor to full throttle and observe the current and power readings. Make sure they are within specs for the motor, ESC and battery. Change to a smaller prop if they are not. Weigh the plane with a battery and make sure your power fits the profile of plane you have per section 9a configuring power system.
Center of Gravity:
Mark a small dot on the bottom of the wings where the manufacturer specifies the center of gravity, usually about 1/3 of the way back from the front edge of the wings. Make sure the plane is level when you place you fingers on the center of gravity. If not move the battery forward or back until the plane is level with your fingers on center of gravity. If you are going to err, do it a little on the side of two far forward. The plane will tend to nose down, but you will most likely still be able to control with a little up elevator. If it’s too far back the plane tends to stall and then spin down crashing into the ground before you even know what happened.
15> Required Equipment for Electric flight
a> Plane, motor, esc, battery
b> Transmitter and receiver radio
c> 2-4 servos (depends on plane)
d> Battery charger and balancer or combo
e> Inline power meter
16> Flight Checklist
a> Battery fully charged? (are you sure?)
b> Control surfaces trimmed, correct direction and functional?
c> Transmitter battery fully charged?
d> Does motor/power level sound correct when ramping up to full throttle?
e> Is the plane in good working order, nothing damaged?
f> All hardware is tight?
g> Correct plane selected in transmitter memory?
h> Center of Gravity correct?
i> Is it too windy for your plane or experience level? If so don’t fly..
j> Is it safe to fly? No people on the field?
k> Is there enough daylight to fly?
k> taking off into the wind?
17> Field Considerations
When first starting out, start at a field with other flyers, see AMA directory in step 1. Ideally you should be working with an instructor on a buddy cable for at least your first couple of flights. If you don’t have a buddy cable, have the instructor do the take off and landing. Once the plane is up high enough to allow recovery from some errors, then the instructor can give you the transmitter. Make sure they first trim it to fly straight and level when you take you hands off the stick, that way if you get into to trouble you should be able to let go of the sticks and the plane should level out.
If you are flying at a non-sanctioned AMA sanctioned field, your AMA insurance is not valid. Also if you are using a 72MHz radio, you can unknowingly cause or receive radio interference with other flyers, especially when you are within 3 miles of a sanctioned field. This can cause your plane to crash or potentially cause others to crash. If you choose to fly at a non AMA field make sure it’s large enough for your plane, and at least 3 miles from an AMA-sanctioned field. Good rule of thumb is 300x300ft minimum for a park flyer. Avoid any wind above 5mph. Also note that wind typically increases when you get above the tree line. Avoid fields with tall objects like light towers, they are a magnet for a plane. Keep the plane close, try doing big circles in front of you. When the plane is far away it’s hard to tell what direction its going, or if it’s upside down. Always keep the plane upwind from you, they get away fast when they are down wind. Don’t fly if there are other people on the field. If you hit them, you are liable.
18> Flying Pointers:
- NEVER fly your airplane towards or above spectators. Always keep flight paths perpendicular to spectators. If this is not possible at the field you are at don’t fly.
- Never allow spectators or other flyers to stand in front of, or to the side of a moving prop. If someone moves into this zone, shut the motor down.
- take off full throttle into the wind
- do a gradual clime to 50ft, altitude is your friend
- once at a comfortable altitude pull back the throttle to 50%, a little more if necessary to keep altitude.
- avoid drastic stick movements, make minor adjustments
- if you have the stick all the way to any extreme, you are not making minor adjustments
- concentrate on keeping the plane close to level
- don’t do radical changes in altitude or sharp turns
- keep the plane close so you can see orientation
- when turning initiate the turn with small aileron movement in one direction to tip the wing, then go back to center, and give a little up elevator through the turn. When the plane is headed in the new direction you want, then get the plane back to level by moving the aileron in the opposite direction. Don’t ride the aileron through the turn, the plane will tend to go into a spin. Use the aileron to start and finish the turn, use the up elevator through the turn.
- If you get into trouble, go full throttle and pull back on the stick and level the wings with the aileron.
- If somehow you get the plane upside down, don’t panic. Give the plane down elevator, since you are upside down this will make the plane gain altitude, and a little throttle. Once you get the plane flying level or gaining altitude you can do a half roll with the ailerons to flip the plane back over. Another option is full down elevator and make the plane do a loop until its right side up again.
- Practice lining up the plane to the runway flying into the wind, and flying a straight line
- When you want to land, line up to the runway, cut the throttle and glide onto the runway. Keep the wings level using the aileron. Keep the plane lined up with the runway using the rudder. Keep the nose up just a little with the elevator. Right before the plane is about to land give a slight up elevator or flare, and the plane will land softly.
FAQ:
What if my spouse/parent says RC flying is too expensive?
- The cost per hour is very low, once you purchase the equipment especially with electric. You will get your money’s worth on a cost/hour basis from flying simulators, building, flying and interacting with other hobbyists.
- For those of us with kids, flying is a great chance to bond in a common interest with our kids. We are developing a life long sport that we can enjoy together even after the kids are grown up and come home to visit. Plus RC airplanes help develop an interest and love for technical skills and engineering.
- RC flying is a relatively cheap way to get through a midlife crisis (this one really worked for me) compared to rebuilding stock cars, flying real airplanes or an affair/divorce.
After flying for a while the motor shuts down
- Once the ESC detects a low battery it will shut off power to the motor so you still have enough power to steer the plane to a landing. Don’t really on the ESC to tell you when your battery is low, you should know about how long the battery will last before flying and land earlier. You run the risk of over discharging the battery if you let it run all the way down.
Right after the plane takes off it goes up a little, noses over and spins into the ground.
- Check center of gravity, control surface alignment, current direction and functionality.
When I pull back on the stick when taking off the plane noses forward instead of taking off.
- elevator control is reversed
One of the cells in my Li-Po pack is swelled up
- pack has been overcharged, or over discharged. Follow manufacturer’s disposal directions.
Plane doesn’t develop enough power to clime off the runway.
- check the battery, is it correct one for the plane, correct voltage/capacity and is it charged
The plane is hard to control, it tends to nose up, especially when I try to turn into the wind.
- too windy to day for your plane/experience level. Center of Gravity too far back
What is wing Loading?
Wing Loading is a good thing to check on how easy a plane will fly. Chord is the width of the wing. The following site will help you calculate it, or use the formula, and do it yourself. This is really and FYI for engineering geeks beginners, if you want to cross check what the manufacturer claims.
http://www.csd.net/~cgadd/eflight/calcs_wingload.htm#formula
Wing
Loading, Imperial
Loading (oz/sq.ft) = Weight(oz) / ( Wingspan(in) * Wing Chord(in) / 144 )
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Wing Loading |
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Loading |
Type |
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10 oz/sq.ft |
Glider |
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15 oz/sq.ft |
Trainers |
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20 oz/sq.ft |
Sport Plane |
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25 oz/sq.ft |
Fighters |