FAQ's

Frequently Asked Questions about electric flight
Thanks to GWS for these FAQ's

Q: What are the differences between Indoor, Slow and Park Flyers?
A: Indoor models are typically the smallest, lightest and slowest of the three, usually weighing less than 8 ounces. Many indoor venues impose a maximum weight limit, often 150 grams. Indoor models have very low wing loadings and use the smallest available cells, 50 or 110mAh being fairly usual, as well as specialized, often coreless motors. Slow Flyers are sometimes regarded as an in-between type, the next level up from indoor models.
The term "Slow Flyer" is often used to describe both indoor models and park flyers. They’re basically small, light and slow enough to be flown in a backyard or neighborhood park, rather than a standard club flying field.
Park Flyers are generally too large or heavily loaded to fly indoors. They tend to use Speed 280-size motors and up, often geared, and batteries up to about 600mAh. They can weigh anything up to 18 ounces, though they’re often quite large and still have light wing loading. They’re also intended for use in relatively small outdoor areas such as schoolyards or local parks.

Q: What kind of equipment do I need before flying?
A: Generally speaking, you need equipment that is very similar to what other RC flyers require. There are only a few primary components: radio, battery, charger, speed control, motor and, of course, the aircraft. The amount of accessories you purchase are up to you, but most pilots typically buy things like a soldering iron, flight box, volt/amp meter, etc.

Q: What tools should I have?
A: There are many normal modeling tools like knives, wrenches, abrasive paper, etc. that are useful You can get started in electric flight with very few specialized tools. There are a few, however, that will make life so much easier that you’ll soon wonder how you ever did without them. Here are a few useful tools:
Soldering Iron: This is essential for general wiring. If you only have one, it should be around 25W. If you’re going to make your own battery packs, a larger iron will help, preferably at least 40W and maybe up to 100W.
Multi-Meter: Buying an analog meter isn’t worth it. You can get a simple digital multi-meter for very little from stores like Radio Shack. If you can get one that will read DC current up to at least 20A, that will be helpful (or see Wattmeter below). But even the simplest will let you measure voltages accurately, so you know what‘s going on in your power system, and will also provide a way of checking continuity so you can make sure all your wiring is intact.
Wattmeter: This device simultaneously measures and displays voltage and current and will also show the total energy used. It’s very much like the displays on most good chargers, but with the great advantage that you can put it anywhere in the circuit and so measure exactly what is happening. It is unbeatable for finding out (rather than guessing) what current you are using and how the battery voltage goes down as the current increases. It will also allow you to measure your own motor constants, which is very useful if you want to experiment with odd (perhaps cheap surplus) motors.
Crimp Tool: Depending upon what type of connectors on which you decide to standardize, you may find it worth getting a crimping tool. The one I use is quite expensive, but makes it so much easier to fit the connectors and makes a much better joint than a soldered joint.
Tachometer: A good tachometer is very useful if you want to do some investigating of electric power sources. Even the most basic of motor parameters involves knowing the speed at which the motor is rotating.
Digital Scales: All planes fly better if the airframes are light, and this is especially true of electrics, where the power package makes up such a high proportion of the overall weight. It’s probably most important to get scales that can weigh small amounts fairly accurately (down to 1/10 ounce), since you’ll be saving weight wherever you can. Some of the best value to be found is the used postal scales that are sometimes available. These will be fine, unless your ambitions lie in the direction of very small and light indoor models. Since the lightest of these have a total flying weight of well under an ounce, you will need jeweler’s scales.Q: What security procedures should I follow when flying?
A: Don't connect the motor battery until you have your frequency pin (or other frequency clearance means) and are ready to either put the plane on the runway or hand-launch. Don't turn on the radio system until you are ready for your flight. Turn off the radio system as soon as possible after the flight. Make sure the throttle is set to off before turning on your transmitter. Many digital speed controls have a function that won't allow the motor to turn until the throttle stick has been in or moved to the low position. Do not make it a habit of testing this function. Motor-on radio checks must be done with the aid of a helper. Check the leading edge and tip of your prop for molding flash, if it's not a wood prop. Carefully sand away molding flash with fine sandpaper.

Q: How do you recommend securing the wings? With glue, or just slide them in place?
A: Sliding the wings in place should be enough. However, if you feel they are too loose, tape around the stick of the wing to make tight.

Q: How is the voltage of a GWS battery pack determined?
A: A GWS battery pack consists of a number of cells, wired in series. Therefore, the voltage for the pack is equal to the number of cells multiplied by 1.2 volts (Ni-Cd cells provide 1.2V of electricity). However, because of a cell's internal resistance, the actual voltage you are getting is slightly lower—closer to 1.1V per cell or even down to 1V in the higher current installations.

Q: How do I calculate the duration of a battery pack?
A: Apply the battery pack's mAh rating to decide how long the needed current can be delivered in minutes:
Duration = 60 X (capacity/1000) / current
Therefore, to calculate the duration of a 1700mAh pack for a 30-amp draw:
Duration = 60 X 1.7Ah / 30 amps
Duration = 3.4 minutes
We can also get a rough but useful estimate by finding it on the ground and then multiplying by 0.75. If your propeller is highly pitched enough so that it is stalled when running static, this number will be far less accurate.

Q: What does mAh (milliamp hours) mean?
A: The milliamp hour is the standard unit of storage capacity for a cell. It is similar to "gallons of fuel" for a combustion engine. The milliamp hour rating of a cell tells how many constant milliamps of current can be supplied by the pack for one hour. This rating can be used to find the duration a battery pack can provide, given a certain draw. Because cells are wired in series, the milliamp hour rating of a pack is the same as the milliamp hour rating of a single cell.

Q: Should I cycle my packs?
A: You will have to weigh the dangers of cell reversal against the dangers of Ni-Cd memory. Some people discharge their packs to 0 volts per cell and say they have never had a problem. Others say that cycling below 1V is damaging.

Q: Can I deep-discharge an individual cell safely?
A: It can be discharged to 0 volts per cell safely. Cell reversal can't occur with individual cells. In fact, cycling an individual cell is a good way to determine its exact capacity.

Q: How does charging current relate to capacity?
A: First of all, make sure of the rate for a given length of charging and use the following rule: Amps = Capacity / Time to Charge. For instance, to charge a 1200mAh battery in 20 minutes requires a current setting of 3.6 amps: amps = 1200mAh / .33 hours = 1.2Ah X 3 hours =3.6 amps. The same rule can also be reworked to determine how long it will take to charge a battery at a given current: Time to Charge = Capacity / Amps. So, the time it takes to charge a 1500mAh battery at 5 amps is 18 minutes: Time to Charge = 1500mAh / 5A = 1.5Ah / 5A = 0.3 hours = 18 minutes. The charging process is not totally efficient; some of the energy is lost as heat, and the charging takes place a little longer than this.

Q: How can I make certain my packs are fully charged?
A: GWS or E-flite™ peak chargers automatically do this. If you don't have a peak charger, we’ll provide the way to monitor the charge yourself. You’ll simply stop charging when one of the following things occurs: either the pack starts to get warm or the charging voltage starts to drop. Warning: if you’re doing a manual fast charge (by watching the temperature and/or voltage yourself), pay attention. If the batteries get too much charge, they will overheat, and that could damage or even destroy your batteries.

Q: What does gearing do for you?
A: Gearing allows a motor to turn a larger prop at lower rpm. This allows the system to produce more thrust while drawing the same number of amps. The trade-off is that top speed is reduced, which makes gearing suitable mostly for slow-flying aircraft. Sport electric planes are usually run with a direct drive system.

Q: How do I compare an electric motor to an IC engine?
A: If you’re looking for a watts-to-horsepower conversion, then the formula is: 1 brake horsepower = 750 watts. The problem is that electric motors have many more variables than IC engines. In order to determine the performance of an electric motor, you must first answer questions such as how much duration you want, how much power you need, etc. Gearing also heavily influences the comparison.

Q: How much heat can our motors dissipate?
A: At room temperature, according to the industry standard, 1 watt per square inch for continuous operation (24 hours). It’s about 3 watts per square inch for GWS motors for as long as a Ni-Cd pack can run it.

Q: How do I keep my motors clean?
A: If the commutator has deposits of carbon and gunk on it, you can clean it with scotch rite or a com stick and very light polishing action. You can also clean off gunk when the motor is running with a few drops of alcohol. If the commutator is pitted or shows brush skipping and chattering, it has been overheated and needs to be returned. It is out of round, and will not be cured with polishing. You need a lathe with a ball bearing in the tailstock and a diamond tool, or at least a sharp cutting tool.

Q: How do I measure motor constants?
A: Of the three motor constants, Kv and Io are much easier to measure.
Kv: With the motor shaft in a drill press running at a known speed, measure the voltage at the motor terminals. Kv = Speed / Voltage. So if the speed is 6000 rpm and the voltage is 3V, then Kv = 6000/3 = 2000 rpm/V
Io: Simply run the motor with no load (no propeller) and measure the current taken. You can use almost any voltage, because the current does not vary with voltage. However, the motor will still be turning at the rpm defined by V X Kv.
Both Kv and Io should be measured with the motor neutral-timed. For most can-type motors, this is where they are fixed. If you do have a motor with adjustable timing, you can try (carefully) adjusting it as you measure Io. It will be neutral-timed when Io is at its lowest value.
Rm: This takes a little more work. The motor and shaft must be held so that neither can move i.e. the motor is stalled. You then need to apply a voltage through a limiting resistor and measure the current through the motor and the voltage at the motor terminals. Note that it must be directly at the motor terminals, not the power supply. You will need to do this very quickly, as the current will be high and the motor will quickly get very hot. Rm is voltage / current. Therefore, if you measure 5A and 1.2V, Rm = 1.2 /5 = 0.24 ohm, a typical value for a Speed 400.Q: How many capacitors do I need on the motor and what values?
A: It’s a good idea to fit at least two capacitors to most brushed motors in order to cut down on the radio interference that the motor may generate. The same capacitors can be used for all brushed motors; the value doesn’t change with the size or power of the motor. The capacitors should be soldered from each motor terminal to the motor case. For extra security against interference, you can also fit a third capacitor between the two motor terminals.

Q: Can I use a 150mAh 7-cell battery with the IPS? What are that motor’s maximum amps? I could use a slightly smaller prop if necessary.
A: You can use a 150mAh 7-cell (8.4V) battery pack for IPS, but you must install heat sink for the motor available as optional item. Max amp for that motor would be 1.2A.

Q: Should I glue the IPS to the IPS mount?
A: There is no need to glue the IPS to the IPS mount. Just press it in.

Q: I have purchased your RC Indoor Power System DX-A with 5.86 gear. Could you please advise me of the maximum current (amps) and maximum number of cells (volts) that I can use?
A: Please be advised that the maximum current for IPS-DX2BB-A is 1.9 amps/hour, and the maximum number of cells is six with a Ni-Cd battery.

Q: I was looking at the Naro flight pack of the package, and I noticed that the receiver battery is 6.0-7.2V 110-270mAh. I want to know if the receiver is limited to 270mAh, or can I hook up 300 or 600mAh?
A: Please be advised that the maximum voltage for our receiver is 12V. However, our servo motor has limited voltage. The maximum voltage for the servo motor is 6V.

Q: Last week, I went into a local hobby shop and bought a slow flyer and one of your R4P receiver packages. I told the clerk I had an Airdromes FM transmitter, and he sold me the JR receiver packages. Will this work with my transmitter?
A: It is correct to purchase the JR receiver for the Airtronics FM transmitter, because the JR receiver shift is the same as the Airtronics.

Q: I have purchased two of your GWRD-8 receivers and was assured that my existing crystals (Hitec dual conversion) would be suitable to use in them. However, I find that my transmitter (Graupner MC 20) will not operate the flight pack. Can you offer any thoughts as to what may be wrong?
A: Please be advised that Graupner MC 20(JR) does not work with Hitec (FP) because of high or low deviation.

Q: I was wondering if your 4-channel and 6-channel receivers could handle a 6V battery. I’m trying to keep weight down and increase flight times. I purchased 6V Lithium batteries.
A: Our receivers have regulator ICs that can take voltage up to 12V.

Q: Please can you tell me the absolute maximum value for the supply voltage for a Pico F Standard servo?
A: 8 microsecond. We would suggest you use a 5-cell (6.0V) battery pack.

Q: Will your servo circuits take a 1-amp stall load?
A: It depends upon which servo you’re talking about. Some might need a 2- to 3-amp stall load because of high output and high torque.