Copterx CX450BA Black Angel Build

Frame assembly

Fortunately, the kit comes with most of the main components (frame, main rotor head, tail gear group) already assembled so it's just a matter of securing everything together. (I had visions of of getting a bag with about a million screws & small parts that had to be individually assembled. I used to put together HeathKits and I still remember creating a wiring harness for one of their TVs from random lengths of wire, each wire cut to size individually, and cable ties.) This kit is a lot simpler but there is still a fair amount of work required.

Note, my unit was an FBL (Fly BarLess) but Copterx is too cheap to create a separate instruction manual so the instructions were for a unit with an FB (fly bar). This is not a problem, you just ignore anything related to a FB and the assembly winds up being just a little easier. (Note to Copterx - an insert that points out the few minor differences and shows the exact parts in the FBL kit would have been nice.)

Pro tip. The FB instructions do create one mistake for an FBL heli. When attaching the linkages to the swashplate the instructions explicitly point out that you use a 23mm linkage. Fine for connecting to the FB but too short when connecting the swashplate directly to the main blade holder. The kit includes the longer linkages, make sure you use them.

Pro tip. Careful with the support structs for the tail boom. You have to glue two end pieces to a plastic rod to create each strut. I neglected to dry fit the two struts properly and wound up with one that was noticably longer than the other. Fortunately I was able to drill a new mounting hole in the longer strut but more attention to detail when gluing the end pieces would have avoided that mistake. (Cyano-acrylic glue is very unforgiving.)

Tail assembly

There's no magic to the tail assembly, just follow the pictures and attach all the pieces as pictured.

Critical pro tip. Although the instructions actually specify the correct way to attach the drive belt to the rear rotor gear it's not very obvious and I got it wrong, with some rather unfortunate results. It is crucial that the belt is attached in such a way that, when the main gear is rotating in a clockwise direction (as seen from above, looking down on the heli), the tail rotor is rotating counter clockwise (when looking at the tail from the right side of the heli with the nose of the heli to your right).

Turns out the tail rudder control arm is screwed on with a left hand thread. If the tail rotor is spinning in the wrong direction this control arm will spin off it's mount (no matter how tight you make it) and the tail will be utterly uncontrollable. Spend some extra time and make sure you get this right.


I found getting the electronics connected and setup even harder than the task of constructing the heli. There's an instruction book, no matter how laconic, for the assembly of the heli. You are basically completely on your own for the electronics.

As I said, I opted for the electronics package from eHIROBO with a Walkera receiver. The specific parts I got were:

3xCopterx CX-9g servos, 1xFusonic MG-D-9257-V2 tail servo
Copterx CX450-10-04, 3550KV brushless motor (that's 3,550 thousand RPMs per volt, with an 11.1V battery that sucker can turn almost 40,000 RPMs under no load - be careful!)
Copterx CX-ESC-40A, Brushless electronic speed controller
Copterx CX-1x2000, mini heading hold gyro system
Walkera RX-601, 6 channel 2.5GHz receiver
USB cable
Copterx CX PB002, usb programming cable for the CX-1x2000
Walkera Devo-7, came with my Walkera V200D03
As I said, buying individual parts I probably could have upgraded the heli but with this package I knew I would get a setup that would work.

Bind your transmitter to the receiver

The first thing that needs to be configured is the ESC. You use your transmitter to do this so that means you transmitter must be paired with the receiver. This process varies depending upon your transmitter and receiver but for my setup the following procedure works:
  1. Mount the motor in the frame. The ESC signals things by making audible tones by vibrating the motor. More on this in the Configure the ESC section.
  2. Connect the 3 heavy duty wires from the ESC to the motor. The ESC motor wires are not color coded so the story I got is to connect them up in any order. If the motor runs backwards (the main blades turn counter clockwise when looking down on the heli from above) then swap any two of the three wires. (Seems a little hap-hazard but that appears to be the rule.)
  3. Connect the remaining lead from the ESC to the throttle channel on your receiver. Fortunately, the connector into the receiver is keyed so you can't put it in backwards (it's not obvious but there's a little ridge on one side of the connector that goes one way into a channel on the receiver slot). I say fortunately because there are other connects you will attach that are not keyed (there's a special circle in hell reserved for engineers that design oriented connectors without keys).
  4. Turn on your transmitter and disable Fixed ID.
  5. Use a small screw driver to depress and hold the clear button under the tiny hole on the RX-601. While holding the clear button down attach the battery to the ESC (have fun doing that by yourself with only 2 hands, it's not that easy).
  6. The light on the RX-601 will flash slowly while the clear button is pressed. Release the clear button and the light should flash quickly.
  7. The transmitter should now find the ID for the RX-601 and the led on the receiver should now turn solid red. If this doesn't happen after about 10 seconds you might need to power off and then on your transmitter.
  8. If the RX-601 led is solid red then the transmitter and reciever are bound together, you can now program the transmitter to use the fixed ID that it now has for your RX-601.
Congratulations, you've now bound your transmitter to your receiver and can proceed to configuring the ESC and the gyro.

Configure the ESC

The ESC actually came with an
instruction sheet that gave instrucitions on how to configure it and what are the proper values to use. You configure the ESC by powering it on when the throttle is in its maximum position, e.g. throttle at 0% at startup => normal operation, throttle at 100% at startup => program mode. Just listen for the magic tones from the ESC, follow the instruction sheet and you'll be fine.

Although there are fail safes (the ESC isn't supposed to provide power to the motor if the throttle is not at 0% at startup) you might want to seriously consider removing the gear from the motor when configuring the ESC (or at least remove the main blades for this step). The last thing you want to have happen is to have the motor spin up and have the main blades rotating at high speed while the heli is on the bench.

Pro tip You have to configure the ESC with the motor attached to the frame. The ESC generates programming tones by vibrating the motor which then vibrates the frame, effectively using the frame as a speaker. By itself the motor produces almost inaudible sounds.

Connect receiver to gyro

This is a little confusing because, at first glance, it's not totally clear why there are so many connections and, on a cursory look, it doesn't appear as if there are enough cables to make all the connections. Never fear, everything you need will be there in the electronics package.

One issue is not having enough connectors. Turns out the Copterx 3x2000 gyro that I'm have has a 3 to 1 cable for some of the connections (a single port on the gyro fans out to 3 ports on the receiver). Combine that with the simple cables in the package and you should be fine.

Tangent on helicopter versus fixed wing controls. A normal fixed wing plane uses 3 controls - elevator (the horizontal flap in the tail that tilts the nose up or down), rudder (the vertical flap in the tail that tilts the nose left or right), and the ailerons (the flaps on the end of the winds that tilt the wings up or down). A helicopter uses the same 3 controls to accomplish the same effects execept the rudder signal affects the tail rotor, the elevator signal changes the front/back tilt of the swash plate and the aileron signal changes the left/right tilt of the swash plate. A helicopter needs a 4th control, pitch, that raises/lowers the swash plate to make the heli go up and down. Since fixed wing planes don't normally have a pitch control (we're ignoring planes with variable pitch propellers, I guess those aren't too common in the RC world) we need a 4th control channel, typically the aux channel, to control pitch.

Back to the wiring setup. From the last paragraph you see we need 5 signals (did you forget about the throttle) to control the heli - throttle, elevator, rudder, aileron, and pitch. For this gyro you also need a 6th signal, gyro gain, but the RX-601 is a 6 channel reciever so we're OK. For the extra heli control signals we're going to use the receivers AUX1 channel to control pitch and then use the Gear channel to control gyro gain.

The following tablel shows the exact cable connections from the receiver to the Gyro:

Receiver -- Gyro
Elev -- Ele (pit/ele/aux - Red)
Aile -- Ail
Thro -- ESC
Rudd -- Rud
Gear -- Aux (pit/ele/aux - Black)
Aux1 -- Pit (pit/ele/aux - White)

Notice how we changed the meaning of the Aux channel between the two devices. Sorry about that, those are just names, the important point is that the right signal from the transmitter will be sent to the right servo with this layout.

Next we have to connect the servos to the gyro. There's a handy little chart in the 3x2000 manual that shows the servo layout for various swash plate designs. The Black Angel uses a 120° layout so the servo connections are:

Servo -- Gyro
Front right -- CH1
Front left -- CH2
Rear -- CH3
Tail -- CH4

Pro tip. Back to my rant on keyed connectors. On my setup the gyro jumbo port (pit/ele/aux) and the Rud port get keyed connectors, all the other connectors on the gyro are unkeyed and can be inserted backwards. Not a problem as long as you make sure you insert the connects such that the White lead is on the front side of the Gyro. Of course, the connector for the tail servo doesn't have a white lead, make sure the Orange lead is on the front side of the Gyro for that connection.

Pro tip. Yet another rant on keyed connectors. Likewise, the receiver throttle port is the only one that gets a keyed connector, all the others are unkeyed. Again, use the White lead for orientation and insert the connectors such that the White lead is closest to the lettering. The 3 cables from the Gyro jumbo port have various colors, insert those 3 connectors such that the single lead, of any color, is closest to the lettering.

Installing the electronics

Installing the 3 electronic components (ESC, receiver, and Gyro) is open to personal preference, there are no hard and fast rules. You want to mount them close to the center of mass of the heli (cut down on rotational inertia effects) but you can put them pretty much where ever you want. I chose:
On the little shelf just below and behind the main gear. You can stuff excess cables inside that cavity behind the receiver, just make sure the cables stay away from the main gear.
Vertically oriented against the side of the frame right next to the receiver.
Attached to the right side of the frame just below the main gear.

I'm using 20 lb. double sided mounting tape to attach the components, it seems sturdy enough to hold them in place. A cable tie around the Gyro and ESC would probably provide a little extra piece of mind and is recommended.

Configuring the gyro

Pro tip. Buy the USB cable for the 3x2000 gyro and configure it from a computer. Theoretically you can program the gyro with your transmitter (simlarly to the way you configured the ESC only you use the leds on the Gyro rather than tones) but I can't imagine getting it right. Buy the cable and configure with your computer, you will be much happier.

Using the computer to configure the gyro is very simple.

  1. Plug the cable into the Gyro (the plug is keyed, it only goes in the right way.
  2. Power up the heli with the battery. I make sure my transmitter is powered on first, I don't like the idea of the heli randomly deciding to spool up and spin the main blades.
  3. Plug the USB cable into your compute and startup the program. Zip file containing the program is available here.
  4. Click on the Connect button to link the program to the gyro.
  5. Click on the Setup button and follow the pages to configure the gyro.

That is all that it takes to configure the gyro. A couple of points you want to consider for your configuration:

Pro tip. The electronic swash mixing is done by the 3x2000 gyro, not by your transmitter. I didn't realize this when I started out and I tried to program my transmitter for a 120° swash plate and the servos were moving all over the place. Turns out the proper solution is to just program your transmitter for a normal swash type and do all the swash mixing inside the gyro.