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Jan 25, 2011, 12:07 PM
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Nine Eagles Solo/BravoIII/Draco FAQ (also for rebranded ones like Revell ProtoCX etc)


Since this little coaxial is quite popular, it seemed like a good idea to start a FAQ. Especially since a lot of good info is buried deep into the various thread about these helis. One thing to observe for this thread, postings like "I like this heli and fly with it all day" or "where can I find this heli at a good price?" other things that are not really technical issues are better suited for the general Solo/Free Spirit or Bravo III thread: and

Announcement! Since I am using the Solo Pro FAQ as base for this FAQ, it might be that some parts mention this heli where it should read "Solo" or there are some things listed that are not valid for the coaxials. I will delete those portions ASAP, and add more coax specific information bit by bit.

Disclaimer: I do not work for Nine Eagles or sell helicopters. Most of the information listed here is from personal experience, or found on this or other forums. So I don't claim to be the inventor of the tips listed here. Do you see some reference to a discovery you made, see it a a compliment please. Usage of this information is purely at your own risk. This FAQ is a Work in Progress, so missing information will hopefully be added as this topic gets older.

First Impressions:

Q 1: I have a Revell Proto CX, Merlin Tracer 60, Hype Freestyler, etc... and it looks just like the Solo. Is my heli an illegal copy?

A:There is nothing wrong. Nine Eagles also produces units that are rebranded. Most of the times this means you only get a different canopy and tailfin, but the heli is the same. Parts from the Nine Eagles Solo should and will fit (except the flybar, since they changed the head slightly on the Bravo III). Or if you have a Solo, parts from Revell etc will also fit. Also, you may get better warranty conditions when getting a rebranded Solo, for instance a big company like Revell seems to have better than average custumer service, although a good shop will replace faulty items no matter what the name on the box. So whatever brand you choose, you are basically getting the same heli.

Q 2: The leds are flashing when I insert the battery, and also when I throttle up. Is something wrong?

A: The leds on the receiver board serve as indicators. When inserting the battery, the blue led will become solid, then start flashing, and finally become solid again, indicating the heli is ready, and connected to the transmitter. If it keeps flashing blue, either you forgot to switch on the transmitter (aka TX) or the heli is not "bound" to the TX yet or lost binding. How to (re)bind your TX and heli is listed in the "other problems" section.

When your heli is connected to the TX, and you apply throttle, a green led will start to flash on the receiver. This indicates the board is sending a throttle command to main and tail motor. This can help with trouble shooting. If you move the throttle stick, and the green led flashes, the receiver is sending signals to the Electronic Speed Controller (or ESC) on the board. If the motors still don't turn, either the ESC has gone bad, one or more motors are bad, or it might just be that the motor wires are not securely connected to the board.

Q 3: I keep hearing about different types of head used on the Solo and Bravo III. What are the differences?

A: The flybar on the Solo is a little brittle, and can snap loose easily in a crash. To counter this, the type of flybar was changed on the Bravo III. It uses the same flybar as the Solo Pro, which is fixed with a small metal pin.

Q 4: Why are there 2 types of balls on the top of the swash? Which ones should I use?

A: Stock the Solo comes with the links attached to the short balls. You can't use the long balls, since the pins on the shaft are not long enough to keep guiding the links between swash and blades. The reason the swash also has long balls is because the Solo Pro FP uses them. Having both types of balls on the top of the swash means they manufacturer only has to produce one swash for both helis.

Q 5: I see these copper colored wires coming from the back of the receiver, but these are not connected to anything. Is that a problem?

A: Those copper colored wires are the antenna wires. These should only be connected to the receiver, and not to anything else. Also beware that they don't interfere with any moving parts. On the RX-01 receiver there is only one single antenna, so don't think it has fallen off.

Q 6: I have a good transmitter already (Dx6i, or other brand/type) can I use that to fly a Bind & Fly version of the Solo?

A: Sadly, no. The 2.4 GHz technology offers some advantages over the older MHz types, but with it manufacturers decided to each use their own control protocol. As a result of that, you can only fly a heli from brand "A" with a transmitter (also referred to as TX) from brand "A", and not with one of brand "B". There is a way to fly a Solo with the aforementioned Dx6i, but that requires replacing the complete receiver with the one from the mCX or mCX2, which is Spektrum compatible. No easy task, and mCX recievers are about the same price as a complete RTF Solo, if you manage to find a good deal.

Q 7: What are the differences between the Solo, Free Spirit, Draco and Bravo III?

A: The Solo and Free Spirit only differ in canopy and the color of the blades and skids. With the Free Spirit these are made of glow in the dark material, to create an "eerie" appearance when flying in the dark. The Draco looks very different, but is still basically a Solo underneath. It just has a complete fuselage, consisting of a front section, and a tail section. The Bravo III not only looks different, but is also more different than the other versions. Besides the obvious lovely Hughes 500 canopy, it uses a different landing gear, different frame, different inner shaft, and different flybar, like discussed earlier, when the head differences were mentioned.

Q 8: The tailrotor barely moves, is that normal?

A: Yes, it is. On a coaxial helicopter the tail rotor is pure for decoration, it has no real function. The main rotor's wash, or airflow around the heli might cause it to spin a little, but that's all.

Q 9: What is the purpose of those little square holes in the side of the canopy?

A: As you may know, the Bravo III is also available in camouflaged version. For those who want to fit guns to their heli, Nine Eagles put those little square holes in the canopy's sides. The following pictures show this:

And those can fit right in:

Q 10: Can I control a BnF Solo/Bravo III with my current Nine Eagles transmitter?

A: If you previously bought another Nine Eagles micro heli, there is a good chance you can use the TX that came with your RTF set to control a seperately bought Bravo III for instance. This even holds for rebranded ones, like the Revell Proto CX, you can use that transmitter to control a Bravo III, and even the single rotor FP helis like the Solo Pro I/II/V1/V2, or Bravo SX. Beware though, more recently released helis, like for instance the SP 328 and SP 270, use a different control protocol, so you can't use the RTF tx of those to control a Bravo III, or control a BnF SP270 with your Bravo III TX!

The more "hobby-like looking" Kestrel 500 transmitter can also be bound to the Solo series. Currently Nine Eagles is about to release a new 6 channel TX, that has model memory and other advanced features. But it is not clear yet if these can be used to control the sub micro helis like the Solo or Bravo III

Beware! Nine Eagles also make micro planes, and their TX looks just like the ones supplied with the helis, but you can't bind a Solo to a plane TX, or the other way round. A very strange decision of Nine Eagles, so it seems, and the reason for this is yet unknown, but at the moment this is how it is.

To give an impression how a Solo and it's "relatives" look in the air, here are some vids.


RC Nine Eagles Solo Helicopter (0 min 56 sec)

Bravo III: - Nine Eagles Bravo III (3 min 14 sec)


DRACO NINE EAGLES (3 min 12 sec)

Flight Behavior

Important general remark before first flight: Since the lineair servos used on this heli have mechanical limits, check if no servos are jamming or getting very close to jamming on full stick deflection. This test should be done on full rates, so with a "full circle" on the display of the transmitter, so you are getting the maximum servo throws. If a servo has less than 1 mm play at one of the endpoints, use the EPA-procedure, listed under the header "Trim Issues" for how to perform this adjustment. Observing this might save you a broken receiver board.

Q 1: When I go a little rough on the controls, the heli suddenly drops out of the sky. What is happening?

A: A little coax like this doesn't like to bank much. When you go fast forward, and then make a hard turn, the heli is forced to bank, but this can cause the rotor blades to suddenly lose lift. Sometimes you can recover from this situation with full throttle, but not always. So the key is to not make hard turns at higher speeds. Using a heavier battery, like the Hobby King 150 OEM also helps.

Another thing that can happen, is that you are flying through the air the blades have disturbed. This can cause such a downwash, that even on full throttle, the heli will still descend. Most small helis can suffer from this when flying in smaller areas.

Q 2: How do I trim this heli for stable hover?

A: First, make sure you have enough space, so you don't run into a wall before you are ready trimming. It usually more convenient to trim the tail first. You can do this in the air, or if you feel uncomfortable doing that, you could try "rough tail trimming" on the ground. Put the heli on a smooth surface, then carefully add throttle to a point where the heli will get a little "light on the skids" but can't take off yet. If the tail is badly trimmed, the heli will spin on the ground. Add some tail trim in the right direction to make the tail stop moving. The reason this could be called "rough trimming" is because the added resistance of being on the ground will affect trim.

When you (finally) get in the air, make sure you are well above the ground. If you are too low, the rotor wash will bounce back, and disturb the heli. Again, focus on the tail first, then, when this is holding well enough, take care of the other directions, like elevator (forward/backward) and roll (slide left/right) after that. This heli is so stable, you should be able to reach a setting where the heli will stay more or less in place without touching the TX's sticks at all. If you can't get a good trim, like a situation where 1 click one way is too much, and a click back again too little, check the chapter "Trim Issues" which is more to the bottom of this FAQ.

After trimming, observe if no servo gets too close to it's endpoint, sometimes when a lot of trim is applied, the endpoints setting gets altered a little, and this might be enough to get a servo to jam. If you have such an issue, either use the EPA procedure, or adjust the length of the pushrods instead of trimming on the transmitter.

Q 3: After a crash the heli is not stable in the air and goes all around the place. What is broken?

A: First thing to check is whether the orientation pin on the back of the swash plate hasn't jumped out off the slot that holds it in the proper position. If it is, just carefully bend the guide a little away, so the pin can snap back in. Look at the picture (taken of a Solo Pro, but the swash guide is identical) to see how a dislocated pin would look like. You can see the pin on the back of the swash is now in front of the guide, instead of sliding between in the guide's rails..

It can also be that the blade pivots have sheared of the head on either the upper rotorblades, the lower ones, or, if you are really unlucky, both. The picture below this shows how broken blade pivots might look like. Observe that the blades are no longer perpendicular to the shaft, but at a different angle. What to do about this is covered under the header "repairs".

Q 4: I am having trouble maintaining a steady altitude with my Solo? What can I do?

A: The Solo is indeed a little touchy on the throttle, because it is very light. Sometimes that makes it hard to find a sweet spot and your heli will be going up and down. Part of the problem is probably lack of experience, especially if this is your first 4 channel, and you are not used to have throttle and rudder (if you are flying mode 2) on the same stick. This will improve in time, but there is also another way to help. Using a heavier battery, like the HK 150 (discussed under "Power Options") will tame the throttle response a little, and helps to keep a steady altitude.


General remark about repairs: If a part is not secured by any screw(s), you can assume it is press-fit instead. Like the landing gear or the tail boom. When you need to remove such a part, pull gently but firmly until you feel the part coming loose. Never use considerable force, it's still a small heli, and though quite durable, things can break if you try to rip it apart.

Also, I keep getting questions where to get spare parts. I will provide some options here, but stress that these are not the only vendors offering Nine Eagles (compatible) spares, and if you run into troubles with one of them, I don't feel responsible for "guiding you there". Possible sources are:

ClubHeli -
Miracle Mart -
HopMeUp -
My RcMart -
Hobby King -

Also keep in mind that rebranded helis use the same parts, so look at all your options to see which one offers the best deal for you.

Q 1: What spare parts do I need for this heli?

A: Depends on your flying style and luck. If you don't crash you will simply wear some things out sooner or later. If you crash more, you will need more parts. The skids are a little fragile, at least on the Solo. The inner shaft can also get damaged, most often the pins that hold the blades are sheared off. If you have the older type flybar, the CF rod might break in a crash, so you need a new flybar as well. Apart from that the motors will wear sooner or later, so having a spare set handy might be wise.

Q 2: After a crash one servo is binding and buzzing.

A: First check if there is no dirt on the little metal axis that drives the servo and on the gears. A grain of sand, dust or hairs can cause lockups. Second thing to check is if the big white gear on the servo axle has not been pushed up, so there is not sufficient play on the servo axle. There should be half a mm or so. If too tight, you can wiggle the gear down a little with a very small flat screwdriver between gear and servo casing.

Q 3: Can I use spare parts from other helis? I broke something and the local hobby shop has no Solo spares...

A: Well, you can in some cases. Like discussed before, the rebranded Solos are identical, so you could also fit Revell Proto CX parts on. Also some parts from other Nine Eagles micro helis will fit. The locking collar on the main shaft is the same as the one used in the Solo Pro/Bravo SX. Also the links between swash and mixer arms on the blades are the same, so you could use a linkage set of the single rotor helis. The swash is also indentical, just remember to put the links on the shorter balls.

It's also good to know the Nine Eagles Twingo uses the same inner shaft as the Solo/Bravo III etc. The inner shaft of the popular eFlite Blade mCX can also function as a direct replacement for the Solo inner shaft. But you do have to use the mCX top rotor blades as well though, and the mCX flybar. However, if you can't get the original parts, and your local hobby shop does have the mCX parts in stock, you can get your Solo up in the air with those instead.

Q 4: One of the pins that holds the landing gear to the frame snapped off, and is now stuck inside the hole in the frame. I can't get it out, help!

A: This seems like a tricky situation, but there are a few ways to get the remainder of the pin out. You can use a smal drill bit to drill a little hole in the broken piece and then thread a small screw into it as far as possible. Then pull the whole thing out with pliers. Another method is using a heated paperclip, or a another small metal pin, and press it into the broken piece that is stuck. Let it cool down, then pull it out with pliers.

Q 5: The links between swash and blades keep coming loose in flight. They also snap on very loosely, but I don't have a spare linkage set...

A: The little holes in those links wear out sooner or later, no doubt. Besides replacing them, there is a way to repair them with thin CA glue. Get a thin object, like a toothpick or small flat screwdriver, put a tiny drop of glue on, and make a circular motion inside the hole that has a too loose fit, coating the inner sides with a thin layer of CA glue. Let this cure for a good period of time (we wouldn't want the glue to be a little wet and then find out the links are permanently glued to the swash plate and mixer arms, no do we?) and then fit them back on. If there is still too much play, repeat procedure, but usually one time can fix this link for many flights.

Q 6: I broke my Bravo III flybar and can't remove it to replace it. Help!

A: The metal pin holding the flybar is press fit. Essential is that you have something to push it out with, something small enough to fit in the hole that the pin sits in, without getting stuck or damaging the inside of the hole. Try to get a small flat precision screwdriver, put that on the pin, and gently but firmly press while holding the head with your other hand. The pin is only held in place by the flybar, so you only get resistance from that. Don't use force, but even pressure to slide it out.

Q 7: My blade pivots sheared off in a crash. Can I glue them back on?

A: You can try, but it won't be very strong. On the single rotor helis you could drill a hole through the shaft, but on the coaxials that won't work. One shaft has the inner shaft running through it, so you can't put a straw or other alternative blade pivot material through, and the head on the inner shaft has the metal axle running almost to the top, so that also prevents any drilling. If glue won't hold, only a new inner or outer shaft will get you flying again.

Q 8: I had to replace the receiver and it came without wires attached. Where do the wires from the battery connector go?

A: On the bottom right of the front side of the circuit board (the side where the servo motors are) you'll see 2 solder pads marked "B+" and "B-" indicating battery positive wire (red) and battery negative wire (black) placement. The next picture will show this.

Even though the receivers on the picture are not Solo receivers (although from now on all micro helis use the same board, RX-01, only with different programming depending on in which heli it is fitted) the places where to attach the battery wires are identical. This picture shows a Bravo SX board on the left side, explaining the extra wires (from the navigation lights) and a Solo Pro one on the right. The solder pads on the receiver are quite small, so you might want to practice first if you don't have much experience with soldering on such small objects. It might help to remove the right servo motor on the picture, to give more clearance.

Q 9: When I try to put the linkages back on the balls, they won't snap on again. What is wrong?

A: Sometimes the fit can be a little tight, but it might also be that you are trying to put them on the wrong way. Every link has a bigger hole on one side, and a smaller on the other. Observe this, and always put the bigger hole on the inside.

Q 10: How do I get the canopy off?

A: This is fairly easy. The canopy is held on the frame with 4 rubbery washers, that sit on the connector pegs on the frame. Remove the small washers on all 4 pegs (careful not to lose those!) and you can slide the canopy off easily. The canopy is made from very flexible material, so if you do it gently, nothing will get damaged.

Q 11: How do I replace the motors?

A: This is a fairly simple procedure. The motor are press-fit in the frame. The only thing to observe is that there is a little notch on top, that prevents the motor from sliding up. Push that aside a little, and then push the motor up. Before disconnecting if from the board, observe where the wires go, and what color is on top. If the motor is held a little tight, you can use a blunt screwdriver or other strong thin pointed object to push the motor up. Replacing the motor with a fresh one is just a matter of pushing it down in the slot.

Q 12: Can I use the receiver of the Solo Pro/Bravo SX for my coaxial? It looks very much like my current receiver.

A: No, not really. The programming on the coaxial receiver is different. A coaxial turns by speeding up one rotor/motor and slowing down the other. Also, the gyro affects both. With a single rotor setup, rudder is only achieved by speeding up a single motor, the tail motor. With older revisions the receivers used in the coaxials used a different layout, and the gyro was mounted differently, so you could easily tell both receivers apart, but since the introduction of the "universal" RX-01 receiver, they look identical. But the programming is different, so rudder only controls the tail motor in a single rotor setup, or 2 in a coaxial setup. Unless we find a way to re-program a receiver, it can only be used with the heli type it came with.


Generally this is a very maintenance free heli. Parts are small, and so are the forces acting upon them. Lubrication is not really needed, and in most cases might even casue dirt to stick to parts, causing malfunction or excessive wear. There are a few things to observe though, on a regular basis.

- Check if the servo gears are clean. A small speck of sand can cause the servo to jam, and even damage the receiver board.
- Check if the tail boom is still fully pressed in. Sometimes the fit is a bit loose, and it can work it's way out slowly. If it is very loose, use a small drop of CA glue to secure it. That way it can still come loose when you have to replace the tail set
- Check the motor connectors on the board. Vibrations can make them come loose, and cause intermittent contact
- Check all moving parts in the head and the motors for foreign objects, like hairs etc.
- The metal contact strips on the battery can get smudgy from fingers and other things, if the metal looks dull, use a cotton swab with a drop of cleaning alcohol on it to make them shine again, and have better electrical contact.

Power Options:

Q 1: How long can I fly on a battery, and how do I know when to land?

A: Depends on the battery capacity. With the stock 110 mAh cells you can stay in the air for around 10 minutes, although you are pushing the battery and motor to the limit then. My stock batteries didn't last many cycles. A good alternative are the Hobby King's OEM 120 mAh batteries, that offer the same or even more power, and flight times. These last many cycles, one of mine is still going strong after 80 flights. Also remember lipos need to be treated with care. Discharge them too far and they won't last long, and in worst case scenario can explode or catch fire. The lipos for the Solo are small, so the risks are also smaller, but you still don't want to go too far, and destroy your batteries. When the heli can't hold altitude on full throttle, you will have gone too far. Best is to either time your flights or use the throttle percentage on the display of the transmitter to estimate the condition of the lipo. Between full and a well but not overly discharged lipo, there is about 15% throttle difference. So if in the beginning you need say 45% throttle to maintain height, it will be time to land at 60% throttle to maintain height. If you want to be extra careful, take 10% as stopping point. This will be about 7 minutes of flight, 15% will be a little over 8, depending on battery capacity.

The bigger Hobby king 150 mAh OEM battery is also a good option. You don't really need the extra 30 mAh for this heli, but because it is over 0.5g heavier, throttle is less twitchy on the Solo and Free Spirit, since these are lighter than the Bravo III.

Q 2: Can I fly batteries back to back, so directly after one another?

A: Flying batteries back to back is not recommended, at least not indoor. After a typical 8 minute flight in the living room, which will consist mainly of hovering, the motors will feel quite warm. And you can be sure the inside of the motor is much hotter. A cool down of 5 to 10 minutes is recommended in this situation. Outside it may be different, since the heli moves through the air, and motors don't heat up so fast, since the air cools them down. On a hot summer day the same rules like for indoor flight might apply, but with temps around 20 degrees centigrade or lower, 2 batteries in a row, or perhaps even more, will not heat up the motors very fast.

Q 3: I bought a new battery and it won't fit my Solo

A: That is very well possible. Nine Eagles changed the connector slightly when introducing the Solo Pro V-series. Since the Solo Pro has the battery inserted the other way round compared to the coaxial Solo, some inserted the battery with the connector facing forward, and fried their receiver instantly. To prevent this, Nine Eagles added an extra "key" notch on the new batteries, making this impossible. A Solo/Bravo III etc doesn't accept this extra notch so the batteries won't fit. Solution is simple, remove the extra notch (and in case if the OEMs, also file or sand down the edges of the connector, because it's a fraction too big) and the battery should fit well again.

A picture showing a V-series battery and an older one side to side:

Q 4: The Nine Eagles Wall Charger is out of stock everywhere, and I am going nuts having to use the TX to charge my batteries...

A: Don't despair. There are other options. You can use a set of spare Solo skids, or other NE heli that uses these batteries, and a spare USB charger you might have lying around from some 3 channel infrared coaxial. If not, these USB chargers come cheap. Their charge rate is mostly close enough to the NE charger, and they have a cut off around 4.2 Volt, although some chargers have no cut off, since the overcharge protection is located on the battery in the heli the charger came with, and are not suitable as a result. Here's a picture that shows how you can do this:

You can also use these skids to connect the batteries to a bigger charger, that has adjustable charge rates, and use that instead.

Q 5: What other batteries can be used with the Solo?

A: Because Nine Eagles uses a battery connector of their own design, options were very limited until recently. You could only use stock batteries without modding. But Hobby King recently started selling OEM batteries that are much cheaper than stock ones. Despite their low C-rating, implying they are not suitable for high performance use, they actually work very well. Flight times of close to 10 minutes for the 120 mAh version, and even longer with the 150 mAh type, with good power, and they can easily reach over 100 cycles, when treated well. In the next question, just below this one. you'll find some info about things to do before using these batteries, please read them as well if you got the OEMs. The graph directly below this shows how these perform, when compared to the stock batteries. It takes the stock 120 mAh used in the Solo Pro for reference, but the 110 mAh used in the Solo coaxials is not expected to perform any better:

As of november 2010 Hyperion also sells their 130 mAh batteries with NE connector, so if you want more power than stock or the OEMs, but don't want to mod batteries or your heli, this is the best option at this moment. On the lighter Solo you probably won't need this extra power, but on the heavier Bravo III, it might be an option.

Do you want more choices, it is better to solder an extra wire to the skids' contact strips so batteries for the MSR can be used. Intellect/Hyperion 130 mAh is very suitable, and the Thunder Power 160 and Nano-tech 130 are other possible options, although these haven't been tested as extensively yet. The extra wire can be found here:

And the picture right below this indicates where the wire should come. (a picture showing a Solo skid will follow soon) Remember to sand the metal strips a little so solder will hold better, and don't apply heat for too long, or the plastic will melt. You can also decide to solder the extra wire directly to the receiver, but this also has risks involved, since the contacts are close to one servo motor, and some small SMD components...

For those that are comfortable with dissecting lipos, it is possible to replace the MSR style connector with a NE type, of an old faded stock battery for instance, and get a better electrical contact, with more power. There are some risks though, so try at your own risk, and take precautions.

Q 6: I bought those OEM 120 mAh batteries from Hobby King but they won't fit or the heli won't turn on when the battery is in place. I did remove the "key" notch. Cheap crappy batteries?

A: These batteries are quite capable, but have 2 things to observe before use. First, some contamination can be present om the metal contact strips of the battery's connector. So it is advised to clean these before inserting the battery. Take a cotton swab and some cleaning alcohol, and rub the contacts a few time. You'll see them become shiny, where before they were a little dull looking.

Second, the corners on the connector of the OEM batteries are a little too sharp, and need to be rounded off some to make them fit as smoothly like a stock battery. A small precision file, like one that is used for fingernails, will do fine. The picture below shows what corners need some trimming. Use a small file or hobby knife to round of the indicated sharp edges. Test fit regularly to see if fit has improved enough. Picture only indicates this for one side, but repeat procedure at the other side for best results. It may take a few minutes, but these batteries perform well enough to warrant the extra effort in making them fit perfectly.

Q 7: Okay, so now I have some batteries with Eflite style connector. Can I use my NE wall charger to charge those?

A: Oh yes, you can, but it requires some modding of either the charger or using an old battery. Modding the charger is quite straightforward, open it up, and solder an extension wire, like you used in the heli, to the terminals inside the charger. Red is + and black is - like is to be expected. Make a little hole in the charger's case for the wire to pass through and close it again.

There is also a method that leaves the charger untouched, but like I said, uses an old battery. You need to remove the connector from the battery, and then solder the extension wire to the terminals inside the battery connector. Other benefits are that you can easily measure the lipo's voltage, since a multimeter can be used to make contact with the NE connector's contact strips. Here are some pictures to clarify this method:

Q 8: Can I use rechargeble batteries in the transmitter?

A: You can, and when you use the transmitter to charge the batteries of the helicopter it might be wise. Just beware that voltage of rechargable batteries (unless you have alkaline based ones) can be lower than of standard, one time use, batteries. Better is to charge the heli's batteries with the Nine Eagles wall charger, and just put alkalines in the TX. Flying this way, I am still on the TX batteries my heli came with, and do fly regularly. Just watch the battery indicator on the TX's display carefully. When you have just one segment lighting up, it might be wise to change to a fresh set of batteries, to avoid range problems when flying outside. This may even apply to inside, since some devices in your house can interfere with the 2.4 Ghz signals your Solo uses.

Q 9: My TX "eats" batteries, is something wrong or why does it consume so much energy?

A: My guess is you are using the TX to charge the heli batteries. This will deplete them very soon. If you use a wall charger for the lipos, and just use the TX for controlling your heli, batteries can last up to months, even with daily flying. The AA batteries that came with the heli might last a little shorter, since these are not high grade, but regular brands, that have a good reputation, will last much longer.

Q 10: I have a Revell Proto CX and use the TX to charge the lipo. According to the manual the charging light should go off when the lipo is fully charged, but it starts blinking instead?

A: This seems to be an issue only with the Proto CX batteries, which have a little Low Voltage Protection circuitry built in. Jtravel asked someone at Revell directly about this, and it was confirmed a blinking light means a charged battery, so the manual is not fully accurate there. Some users report that the light will go out a while later, but based upon current information you should remove the Proto CX battery when the light starts blinking. If you want to be sure the battery is fully charged, test with a voltage meter, it should read around 4.20V, might be a little higher when just coming of the charger.

Q 11: How long does it take to charge a battery?

A: That depends on how much was drained from it the flight before. I did some measurements and found that for about every minute of flight, you need about 3.5 to 4 minutes to charge back what was used from the battery. So if you were to fly for 7 minutes, charge time would be around 24.5 to 28 minutes to get it fully charged again. This is using the NE wall charger. Results may vary a little, as some chargers might have a higher or lower charge current, and it also depends on your flying style. My typical Solo flights consist of a little hover, some figure eights or circuits, some nose or tail in circles, and sometimes a little precision landing practice.

Trim Issues:

Q 1: I need almost maximum trim to hold the tail straight. This can't be good, right?

A: This can be a sign one of the motors is much stronger than the other, or one is failing, but it can also be that your base setting for the rudder stick is way off. You can adjust this with the TX in mode 2. Power up TX and heli, then press the little button on the back of the TX a few times in quick succession. The button is located near where the antenna is mounted. You will hear a beep and notice all trims are set to neutral. Now you can fly like usual (except the rudder stick will do nothing!) and make trim adjustments, but you won't see the trim indicators moving. Adjust the tail trim until it is holding well, and land the heli. Press the little button on the back one more time to hear an affirmative beep the new setting is locked in. Now trims will move again, but since the tail is holding with the new setting, you have equal “trimming space” to both sides again. You may also notice the tail responds better in both directions.

Q 2: I need almost maximum trim for elevator/aileron to keep steady hands free hover.

A: In this case you have 2 options. You can use the sub trim method, like with the tail motor, or adjust mechanically. This means carefully snapping off the links between swash plate and servos, and turning the plastic connector a turn, before snapping it back on. This is especially recommended if the trimming makes the servo be very far away from centre with the sticks neutral.

[I]There is also an adjustment for the gyro in subtrim mode. Pressing the throttle trim up increases gyro, pressing it down decreases it. I haven't used it myself but on the Solo Pro it greatly enhances piro rate.

Q 3: I adjusted the servo links, but trim became worse, and I forgot to measure them so I can't go back to the old length. What is the stock length for the servo arms?

A: There isn't really a stock length, the optimum length varies among helis. Amount of play in the swash, neutral position of the servos, trims and other small differences can affect this. But to have a reference for those that need it, I measured some linkages and got these results. Length is taken from the z-shaped part of the metal rod to the center of the hole in the link that snaps on to the swash arms.

Elevator: ? mm
Aileron: ? mm

Q 4: My servo(s) lock up when steering full movement with the stick. If I move the stick less, it works okay. What can I do?

A: Sometimes a little trimming, and adjusting the link between servo and swash to compensate the difference might work. But otherwise, EPA or End Point Adjust is what you need. This is a hidden mode in the transmitter, that needs a special procedure to access it. As I recall Himalaya was the first to provide this information, and here is how you do it:

(It's not confirmed this will work on the latest RX-01 based Solos. On the older receivers EPA is not available)

**** EPA, or End Point Adj. ****

▲ enter Sub Trim Mode
▲ unplug the lipo of your bird and plug it back in to enter EPA adj.

△ to set Aileron left end point, push&hold right stick to max. left positon, press T4 to adjust, right = less throw, left = more throw.
△ to set Aileron right end point, push&hold right stick to max. right position, press T3 to adjust, up = more throw, down = less throw.
△ to set Elevator forward end point, push&hold right stick to max. forward position, press T1 to adjust, right = less throw, left = more throw.
△ to set Elevator backward end point, push&hold right stick to max. backward position, press T2 to adjust, up = more throw, down = less throw.
▲ press the back button to save&exit when done.

I would recommend to carefully watch the servos move when you do this EPA trim. Stop moving when the servo sliding block is 1mm apart to the hardware limit. Hitting the hardware limit will cause the servo lock up, you may have to manually spin the tiny servo gear to rescue it from the lock-up. The next picture explains what T1~T4 here all stand for. It's the four trims in futaba order, T1~T4 from right to left.

For completeness, this is the link the the original posting which contained this information:

Q 5: Why are there 3 trim buttons for every stick? What do the top ones do?

A: These have no function, that is, until you decide to switch the TX from mode 2 to mode 1. This TX can be switched between modes by simply mounting the antenna 180 degrees turned. Then you turn the whole TX upside down, so the relocated antenna faces up again, and the 2 previously unused top trim buttons have now suddenly become the 2 bottom trim buttons, and control aileron and rudder trim. This means you can still trim those functions with your thumbs easily. I don't think there is a single TX out there that makes switching between modes so easy.

Q 6: Some of the controls don't work. Like throttle stays at 100% even with the stick down. Or a servo will only move one way. Do I need a new receiver?

A: First thing to try is stick calibration. This mode is also covered under "other problems", just below this space. Press down both sticks, so you hear the swithes beneath the sticks click, and hold it there for a few seconds. 3 dotted lines appear on the display, then press down on the sticks and rotate them a few times through all positions, to calibrate sticks' ranges and return the TX to normal operation, hopefully restoring the controls.

If this won't work, or you want to analyze a problem more thoroughly, there is a way to determine if the problem is receiver based, or TX based, by using the simple mode changing feature. Remember, when in mode 2, throttle will be on left vertical stick, and rudder on left horizontal. Right stick vertical is elevator, and right stick horizontal is aileron. In mode 1 this changes to left stick vertical = elevator, left stick horizontal = rudder, and right stick vertical = throttle, and right stick horizontal = aileron. So when you change the TX from mode 2 to mode 1, and the left stick becomes the right one, because you have to turn the TX upside down, some controls are physically changed from one stick to the other. We can use this to diagnose a control problem.

Let's consider some examples to make this more clear. Let's say the elevator servo goes to full forward position, regardless of stick position. When changing the TX to mode 1, elevator physically stays on the same stick, but since the TX was turned upside down, up and down for elevator are also reversed. So if the stick was constantly steering full elevator down in the mode 2 situation, when in mode 1, it should move full up, if the problem is caused by the TX. If it still moves down aka forward, the problem lies in the receiver.

Another example, say the aileron servo steers full right, regardless of stick position. We change the TX to mode 1, and now aileron is controlled by the other stick. If the problem was TX based, we should now have a rudder problem, and the aileron servo would behave normal again. If not, the receiver is the cause.

Q 7: I just unpacked my Bravo III and one of the servos isn't working. What is wrong?

A: Generally the best thing in such a situation is to contact the seller right away, but there are situations where this may not be an option, like when you bought the heli from a seller that requires the buyer to pay for return shipping for instance. And there is a chance you can fix this problem yourself, as it might be an assembly defect. On the next picture you will see that on the skids there are 2 pins that keep the canopy away from the receiver board.

Those pins should fall into 2 little holes on the inside of the canopy, but sometimes they aren't. This can cause the canopy to interfere with a servo, causing it to get locked. The next picture shows how the pin falls into the holes like they should.

When the pins are not in the slots, loosening the screws holding the canopy might give enough clearance to get them in the right spot again. For a third picture and some extra info, check this posting:

Other Problems

Q 1: My TX has locked up in bind mode. I see three lines but they are not moving and I hear no beeps...

A: This is actually a hidden stick calibration mode. It can be accessed, sometimes by accident, by pushing down both sticks (there is a little switch beneath every stick) and holding them down for a few seconds. Getting out of this mode is simple, some like Marconos posted a solution a while ago, but some info was lost in the translation. What you do is press down on the sticks, then rotate both sticks simultaneously through their full range a few times, and the display will come back to normal.

Here is a video that shows how the TX can get locked in this mode, and be restored to normal operation easily:

sbloccaggio radio nine eagles (2 min 7 sec)

Q 2: How do I bind the heli to the transmitter? My manual is in Chinese...

A: In this case the manual of the Proto Max offers support. This is the correct procedure:

Turn on the transmitter. Lower the throttle control stick all the way down. Adjust the throttle trim tab until the throttle trim indicator is centered and the throttle position indicator reads “000.” Turn off the transmitter.
Connect the LiPo battery to the helicopter. Turn on the transmitter while pressing inward on the throttle control stick until the blinking blue light in the helicopter remains steady, indicating that the receiver is reading signals from the transmitter—this should happen within a few seconds.
If it doesn’t work the first time, disconnect the LiPo battery from the helicopter and turn off the transmitter. Repeat the binding procedure again by reconnecting the LiPo battery and turning on the transmitter with the throttle stick depressed. The receiver is now “bound” to the transmitter and the helicopter is ready to fly.

Upgrades and other Mods

Q 1: Are there any metal upgrades for this heli?

A: At first it might seem there are none, but remember some Solo Pro parts will fit. Xtreme makes a metal swash, that can be used, and also the metal shaft locking collar. I suspect even the metal swash guide will fit, since the swash is identical for both types of helis.

Q 2: Do the motors need heatsinks?

A: Small, high speed coreless motors, like used on the Solo, can get hot after continuous operation. Most tend to limit flight times to about 7 minutes (one battery) and then let the heli cool for 5 minutes or more. If you do want to fly batteries back to back, this heatsink mod, Marconos came up with, might help. The heatsink is shown installed on a Solo Pro tail motor, but it can be installed the same way on the Solo's motors:

dissipatore di calore.wmv (2 min 26 sec)

Just remember that a coreless motor can be much hotter inside, where the windings and the brushes are, than on the outside. It is not sure if a heatsink will help to keep motors cool enough after long flights, but it will certainly help some.

Q 3: Can I replace the sticks on the TX to get more control?

A: Not directly, the sticks are not seperate parts that can be unscrewed or so. They seem glued in, and can be removed, but you might damage the stick units doing this. However, you can still make them longer to have more control. You can use bamboo skewers, sanded to fit the hollow sticks, to get more "feel" on the controls.

More info can be found in this post:


"Master Tinkerer" EQMOD also did some amazing mods to his Solo, making it dual swash. More details can be found in this topic:

Big thanks to all who made this thread possible, by supplying information, images, feedback and other help. This FAQ wouldn't have been possible without your contributions. :
Last edited by SoloProFan; Apr 03, 2012 at 08:31 AM.
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Jan 25, 2011, 02:09 PM
Epilepsy Awareness
Flying High Mike's Avatar
SoloPro, I don't own either one of these helis but, I must say it is an excellent write up with OOODLES of information. I know those who do own these helis will certainly appreciate your hard work putting this together. Nice job

Jan 25, 2011, 02:26 PM
Fan of just about anything RC
SoloProFan's Avatar
Thread OP
Originally Posted by Chap1012
SoloPro, I don't own either one of these helis but, I must say it is an excellent write up with OOODLES of information. I know those who do own these helis will certainly appreciate your hard work putting this together. Nice job

Thanks, I am hoping this FAQ will help many pilots, just like the Solo Pro/BRavo SX FAQ is already doing.

I think I've removed most of the single rotor related material now, but I will look at it later today, to be sure. Then I will correct the numbering of the questions.

Btw, can someone who has a Solo/Bravo III or other NE coaxial with RX-01 receiver check if you can access EPA on this heli? I know it doesn't work with older receivers, but I have no RX-01 Solo, so I can't test it myself.
Latest blog entry: For the love of the hobby!
Jan 26, 2011, 03:44 AM
Registered User
Thank you very much SoloPro! I've applied for sticky-status...

EDIT: Just read through the whole thing (again). It really is chock-full of information. Amazing!
I wonder if Nine Eagles is aware of this FAQ?
Last edited by Quagga; Jan 27, 2011 at 09:35 AM.
Jan 26, 2011, 08:14 AM
this is extremely helpful as my bravo III is arriving today. thank you!
Jan 26, 2011, 12:17 PM
Fan of just about anything RC
SoloProFan's Avatar
Thread OP
Originally Posted by Quagga
Thank you very much SoloPro! I've applied for sticky-status...
I did as well, and our combined efforts seem to have worked. Thanks!

Originally Posted by s4pat
this is extremely helpful as my bravo III is arriving today. thank you!
You're welcome and happy flights with your new heli. And if you, or someone else, finds something missing, or has information to add to this FAQ, feel free to post it here.
Latest blog entry: For the love of the hobby!
Jan 26, 2011, 01:26 PM
Rather Be flying or Tinkering
jtravel's Avatar
not a valid concern
Last edited by jtravel; Jan 26, 2011 at 05:52 PM. Reason: not a valid concern
Jan 26, 2011, 01:42 PM
Fan of just about anything RC
SoloProFan's Avatar
Thread OP
Originally Posted by jtravel
I would be very cautious about doing the Motor Heatsink mode on a coax.
Aluminum Foil Tape is conductive and could cause a short if it comes into contact with the 5 in 1 board
With the motors located behind the rotor shaft, I think you would have to make big heatsinks to get close to the 5 in 1. And I think anyone performing this mod would also make certain the foil tape doesn't get to close to the moving parts of the servos that are also between the board and the motors. So I think this is not a real problem.
Latest blog entry: For the love of the hobby!
Jan 26, 2011, 05:27 PM
Rather Be flying or Tinkering
jtravel's Avatar
Originally Posted by SoloPro
With the motors located behind the rotor shaft, I think you would have to make big heatsinks to get close to the 5 in 1. And I think anyone performing this mod would also make certain the foil tape doesn't get to close to the moving parts of the servos that are also between the board and the motors. So I think this is not a real problem.
Yes your right the motors on the coax are located well to the back.
Jan 26, 2011, 05:33 PM
Registered User
kablegod's Avatar
AWESOME job Solo, I havent read it all yet but you have answered 3 questions I had.
Jan 27, 2011, 05:47 AM
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SoloProFan's Avatar
Thread OP
Originally Posted by kablegod
AWESOME job Solo, I havent read it all yet but you have answered 3 questions I had.
Glad to hear that. Makes this FAQ a success already...

Added some info about maintaining altitude during flight.
Last edited by SoloProFan; Jan 27, 2011 at 07:37 AM.
Jan 27, 2011, 03:53 PM
Registered User
The Bravo III I just received from MRC had one of the skid pins not seated in the fuselage. In my case, the up elevator did not work. Unfortunately, the skid was warped and would not allow it to seat properly. The aileron trim button didn't work either so MRC is going to replace the kit.....

I did loosen the fuselage screws and pulled the body away from the skid and the elevator worked again. So it seems that this may become a common issue.
Jan 27, 2011, 04:15 PM
Fan of just about anything RC
SoloProFan's Avatar
Thread OP
Originally Posted by kablegod
heres those photos....
Originally Posted by laarj
The Bravo III I just received from MRC had one of the skid pins not seated in the fuselage. In my case, the up elevator did not work. Unfortunately, the skid was warped and would not allow it to seat properly. The aileron trim button didn't work either so MRC is going to replace the kit.....

I did loosen the fuselage screws and pulled the body away from the skid and the elevator worked again. So it seems that this may become a common issue.
Added now, thanks for the information. Also added some flight vids, a little info about the differences between the various versions, and a question about the tail rotor.
Latest blog entry: For the love of the hobby!
Jan 28, 2011, 10:41 PM
Registered User
malden86's Avatar
What a great post SoloPro, thanks for all your hard work. I got my Bravo III earlier in the week and I already broke a piece on one of my landing skids, I haven't crashed yet but had a rough landing. Does anyone sell upgraded skids or replacement skids?

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