UMX Pitts - Disabling AS3X

I love the UMX Pitts. It flies amazingly well given its size and has plenty of power. One thing that I don't care for is the AS3X. With it enabled it feels like I'm constantly fighting it and am never in complete control of the plane.

While you can't disable AS3X outright, you can set it up so you can toggle it off and on with a switch on your transmitter, which is good enough for me. Unfortunately, this process is a bit of a pain and is documented rather poorly by Horizon Hobby.

I was able to get everything to work on a modern computer running a 64-bit copy of Windows 10. Here's how to do it...

What you need:

• UMX Pitts with a transmitter bound to it
• SPMA3060 USB programming cable
• SPMA3060 software from Horizon Hobby
• The appropriate (32-bit or 64-bit) driver installer from this site (more on this later)

Enabling X-Port

Enabling X-Port on the plane will allow the receiver to be programmed with the SPMA3060 cable. Here is the process that I followed to do this.

1. Turn on the transmitter and hold full throttle and right rudder
2. While holding the full throttle and full right rudder, plug a battery into the plane
3. Hold the transmitter stick in position until you hear two warble tones
4. Disconnect the battery from the plane and release the transmitter stick

It's good to have a helper to hold the transmitter stick while you do this. You can also use a rubber band.

You can use a rubber band to hold the stick in position. I'm using a Taranis with a Spektrum hack module.

Getting the SPMA3060 Cable Working

The second-most annoying thing about this whole process is getting the cable to work properly. The problem stems from it using a Prolific PL2303 USB to Serial converter chipset. I work in IT for my day job and I've had many dealings with this chipset over the years. IMO, this chipset is a gigantic flaming pile of crap, but I'll spare you from a rant.

This page on Total Car Diagnostics' site does a good job of explaining the problem in depth so I won't steal their thunder. More importantly, it contains download links to a working driver.

Once you have downloaded and installed the driver from the link above, you should see the device listed in the Device Manager along with a COM port number. There shouldn't be a yellow caution sign icon by the port. If there is, try rebooting. If you're not sure how to open the device manager, see this article.

Device Manager showing a properly working SPMA3060 cable

Connecting the SPMA3060 Cable

Now that you've got the driver situation sorted out, it's time to connect the cable to the plane. This is probably the hardest part. You'll want to do this with the cable disconnected from the computer and no battery installed in the plane.

The X-Port location is shown below. As you can see, it's tucked deep into the fuselage and is not easily accessible. I used a pair of small needle nose pliers and a healthy does of profanity to connect the cable.

X-Port location

Updating the AS3X Settings

Start by plugging the SPMA3060 cable into your computer, then plug a battery into the plane. After that, navigate to the location where you saved the SPMA3060 software. Right-click the GYRO_PAR_DOWNLOAD executable and Run as administrator. The software won't work correctly if you skip this step.

When the software opens, it should auto-select the COM port. Click the "read" button under the STATE section to read the current settings from the plane. It's not a bad idea to take a screenshot of this in case you ever need them later.

Read settings

After that, set the values in the CONFIGURE section to match the ones in the STATE section (you'll notice that they are all set to 0 at first, but change the "Switch gyro via CH5 ON-1/OFF--0" from 0 to 1. This will make it so that when you have AS3X enabled it will behave the same as it did out of the box, but you'll be able to disable it with your channel 5 switch.

Click the "modify" button to save the changes back to the plane. You should get a "Modify Success!" message when it finishes.

Disconnect the battery and the SPMA3060 cable from the plane, then reconnect the battery. You should now be able to toggle AS3X with your channel 5 switch.

Spektrum Hack Module

I recently put together a Spektrum hack module for my Taranis. These are my notes from that process. If you want more info on what exactly this is, or more technical details on the PCB, this blog post contains the relevant information.

What you need:

• RF module from a Spektrum DX4e, DX5e, or DX6i
• PCB - I got mine from Radiocontronics. The blog post linked above provides details on making your own if you're interested in going this route.
• Case - Horizon Hobby sells a replacement DM9 case that works perfectly. If you have a 3D printer, this is another option.

Getting an RF Module

Since Spektrum doesn't sell RF modules by themselves, you'll have to harvest one from a donor radio. The DX4e, DX5e, and DX6i will all work and give you 6 usable channels. If you don't already have a donor radio, you can check ebay or the classifieds section on RCGroups.

Note that the older SKUs of these radios only supported DSM2. If you're buying a radio specifically for this purpose, I'd highly recommend spending a little extra to get one that does DSMX.

After you remove the RF module, the radio can still be used as a buddy box. If it's in good shape, you may also be able to sell it for parts afterwards in order to recoup some of your money. That's what I did with the DX6i that I used.

Removing the RF Module

Remove the screws on the back of the radio and separate the halves. There will be some wires running between the two halves. Unplug them and and set the back half aside.

If you're not sure where the RF module is, simply follow the cable down from the antenna. On the DX6i the module is socketed. I haven't personally seen inside a DX4e or DX5e, but from what I understand it's soldered to the board, so plan accordingly.

Inside the DX6i

Installing the RF Module in the PCB

The PCB that I got from Radiocontronics has a socket installed. If you opt to build your own PCB, you'll have the option to install a socket or simply solder the module directly to the board.

The PCB from Radiocontronics also comes with standoffs. They work great, but I had to to shorten the pins on my DX6i RF module 2-3mm in order to get them to snap in correctly. I believe that this step isn't necessary with the RF modules from DX4e or DX5e.

Shortening the pins on the DX6i RF module

Putting Everything Together

With the PCB and RF module mated, It's time to install it in the case. First set the PCB into the case and make sure that it fits correctly and that all the mounting holes are free of obstruction.

PCB in the case

If you're using a DM9 case, there will be a button in the package that is meant to be used with the DM9 board and won't fit with this PCB. You can simply leave this out, but in order to prevent dust from getting in the case I affixed mine in place with a drop of thin CA and trimmed off the excess.

Once you've confirmed that everything fits correctly, plug in the antenna and assemble the case.

Setting up the Transmitter

Install the module in the bay of your Taranis and set up a model. Set the Internal RF to off and External RF to DSM2 DSMX.

Taranis with hack module installed

RF module settings

Once that's done, bind the receiver as you normally would. I also found that it was necessary to reverse the aileron and rudder channels.

Final Thoughts

I'm extremely happy with how the module came out. I've used it successfully with a UMX Pitts and a Blade Inductrix. It's nice being able to fly my Bind-N-Fly stuff without needing to bring along a second radio.

At the time of this writing, you can expect to spend roughly $70-$100 to put one of these together. The cost would obviously be significantly less if you already have a donor radio. If you want one of these modules, I'd recommend doing it sooner rather than later because the supply of donor radios will inevitably dry up at some point.

Welcome to My RC Blog!

Welcome to my blog! I'll be posting RC-related content based on things that I find useful or interesting (hopefully you will too).

My RC efforts are almost exclusively focused on planes, and my content will reflect this. That said, I've always been fascinated by RC cars and boats, so I may eventually break down and get some sort of surface craft. I've also dabbled very lightly in multirotors.

For my first post, I figured I'd share my story of how I got into (and back into) the hobby. If you don't care about that, here's the tl;dr version...

I flew for a while, then I stopped flying for a while, then I started flying again.

If you're interested in the whole story...

When I as a kid in the late 1990s, my mom and I were trying to figure out what to get my dad for his birthday one year. She remembered that he had once mentioned in passing that he'd like to try flying RC airplanes one day. We went to the local hobby shop and got him a .40 size ARF trainer and the requisite accessories. I use the term "we" loosely since my mom technically paid for everything, but hey, she let me put my name on the card so it counts :)

Although it was *ahem* touch and go at first, thanks to buddy boxes, the tireless efforts of the instructors at our local flying club, and a healthy supply of glue and spare balsa, we eventually became semi-competent RC pilots.

Me flying a Zagi 400X in 2002

Fast forward a number of years and I moved away for college. With me gone, my dad found other things to occupy his free time and flying fell by the wayside.

Fast forward again to about 6 months ago. I have a few coworkers who are into race quadcopters and sometimes fly them during lunch. They had invited me to come check out their quads after I mentioned that I used to fly RC airplanes in a previous life. I declined at first, but after a few weeks they finally wore me down and I agreed to go with them. As soon as one of them took off, the memories came flooding in. There's something magical about the sound of a prop screaming through the air. I had been bitten by the RC bug again.

Within a week I had ordered a Taranis and a TechOne Mini Tempo 3D. Since then my collection has grown to include a handful of additional planes. I don't know if my skills are quite back to where they were back in the day, but I've at least managed to shake off most of the rust. Now to get my dad back into flying...