This article is coming from the perspective of a complete new build. Once we have our components, we can think about putting it all together. It’s great to plan where you’re going to put things and to test out CG. But, hold on one second. There are a few things that we should do before one drop of solder hits our flight controllers. Before following this guide; make sure you have installed the latest version of iNav Configurator.
Connecting up to iNav
The first thing we are going to do is open up iNav Configurator and plug the USB cable in to our flight controller. This is going to allow us to do 2 things. Firstly, if we see activity on the flight controllers LEDs, we can see that it’s communicating with our computer, and is working. Secondly, we can find out which target is installed.
Check the connection box at the top of configurator. It should show USB followed by a number. If the number is 1, check the drop down list. If only 1 is visible, there is some communications problem. The first thing I would check and change is the USB cable it’s self. Some cables are just dodgy from the get-go. But even decent cables can go bad over time. Ideally, you should use a USB port on the front or back of your computer (or side of your laptop). Sometimes using a USB hub can cause issues.
If you still don’t see a USB number other than 1, and this is the first time you have plugged a flight controller in to this computer. Your computer may need some drivers. You can download them from here. Install them and try again.
Hopefully by this point you have USB 3, for example, shown at the top of Configurator. If so, click the Connect button. If not, you may have a faulty flight controller.
Testing the flight controller and finding the target
Chances are, when you plug in your USB cable and connect, Configurator will take you straight to the CLI page. Don’t worry. Unless your flight controller comes shipped with iNav 3.0, this will happen. But this is fine. What we need to do now is type version in to the CLI and press enter. What you should get back is similar to the following:
INAV/MATEKF405SE 3.1.0 Jun 26 2021 / 14:22:49 (688bff68)
This is showing us a couple of things. Firstly, that our flight controller is communicating with Configurator. We have validated that our flight controller is working. Secondly is gives us the firmware and target installed on the flight controller. Using the above example, we are shown:
- INAV – This is the firmware that is installed on the flight controller
- MATEKF405SE – This is the target that has been used
- 3.1.0 – This is the version of the firmware that is installed on the flight controller
We don’t need the rest of the information. What we need to remember is the target.
If your flight controller does not have iNav installed, you may find that the target shown here is not available in iNav. In which case, we need to find the correct one to use. The first place to check is the manufacturer’s web site. In this example, I am using a Mateksys F405-WING. Mateksys have got great documentation on their web site. And with some flight controllers, the F405-WING being a prime example, the target is printed directly on the flight controller.
However, not all manufactures are as helpful as Mateksys. However, you can see all the main targets supported by iNav in the firmware flasher, which we will look at next.
Some targets have more than one option for how they work. An example is the Mateksys F411-WSE. There is the main target, MATEKF411SE; which works as described on the Mateksys page. However, there are also three target variations. Each offering a slightly different way of working. For example,
MATEKF411SE_FD_SFTSRL1 adds an Rx pad for Soft Serial 1 on the LED pin. You of course loose the LED functionality, but you now have a full duplex (Rx and Tx) Soft Serial 1. You can use this for things like connecting a DJI VTx. For more information on targets and variations, check out the docs on iNav’s GitHub. In that list you will see a lot of .md files; these are the documents. The documents you are care about, in with regards to targets, all begin Board –.
Flashing iNav 3.0
If Configurator is still connected to iNav, click the disconnect button at the top right of the screen. We need to get back to the home screen. The one that you see when you first start Configurator. We need to go click on the bottom option in the menu on the left, Firmware Flasher.
At first glance, this page may look pretty full and daunting. But, there are really only a few options that we need. And the rest of the page is all text. Take a look at the image on the left. In the top drop-down box, we need to select our target. We already chose this in the last section of this article. So that should be nice and straight forward.
The next drop-down box is the firmware version that we want to use. As I type this, the latest stable release of iNav 3.0 is the initial 3.0.0 launch firmware. However, soon there may be a 3.0.1 or even 3.1. So, select the latest stable release. In the next section, there are four select boxes. We just need to make sure that we enable Full chip erase.
Once we have chosen our options, we need to go to the bottom of the page and click the Load Firmware [Online] button. This will download the firmware and the page will refresh. You will now see a Release info section on the page. This contains a lot of useful information for release. If you are performing an update, you must read the notes here for the correct process. However, we are doing a fresh install, so just click the Flash Firmware button.
If all is well, you will see your flight controller enter DFU mode. DFU replaces the USB X at the top of the screen. Configurator will then erase your flight controller. Then install the new firmware; you will see Flashing… in the bar at the bottom of the screen. Once complete, the status bar will show Programming: SUCCESSFUL. Configurator will then reboot your flight controller.
However, sometimes things don’t go to plan. The most common problem here is the flight controller not entering DFU mode. If this happens to you, the simplest solution is to use ImpulseRC Driver Fixer. Close configurator, run driver fixer, then open configurator and try the flashing process again. The Driver Fixer tool is so good, It has never failed me yet.
Selecting your preset
We have now flashed iNav to the flight controller, we can really start setting up iNav 3.0. The next step is to click that connect button. Because this is a clean, fresh install of iNav, Configurator will show us defaults dialogue box.
At this point, we need to decide on what type of plane we are setting up. We have two choices: Airplane with a tail or Airplane without a tail. To make this decision, just take a look at your plane. Does is have something extending out from the back with a horizontal stabiliser? If so, choose Airplane with a tail. If not, choose Airplane without a tail. Just in case, here are a few popular examples.
|Airplane with a tail||Airplane without a Tail|
|MyFlyDream Crosswind Mini||SonicModell AR Wing|
|HobbyKing Bixler 2||ZOHD Dart 250G|
|X-UAV Mini Talon||Reptile S800|
|RiteWing Drak with boom kit||RiteWing Mini Drak|
|Finwing Albabird||Strix Goblin|
|Reptile Dragon II||Reptile Dragon|
|SonicModell Binary||Finwing Transformer|
|Volantex Phoenix 2400||Eachine AR Wing Pro|
|Eachine Razor||C1 Chaser|
Once you click the correct option for your plane, Configurator will update setting and automatically save and reboot.
Calibrating the accelerometer
While we still have the flight controller out of the plane, we’re going to calibrate the accelerometer. Why do it outside? Because it’s a hell of a lot easier. Firstly, click on the Calibration menu option. You will see the calibration page, with the 6 positions to calibrate. Other than calibrating right side up first, the order doesn’t matter.
Click on the Calibrate Accelerometer button, and you will see an instructional box pop up. It’s going to tell you pretty much the same as I am now, so lets just do it!
- Put the flight controller flat on your desk and click the Calibrate Accelerometer button. Step 1 should now light up blue
- Put the flight controller on one of it’s side edges. The double board controllers are great for this, as the will stand up straight. But if you have a single PCB flight controller; you can use a box to make sure it’s upright. Then click the Calibrate Accelerometer button. The corresponding step should light up blue
- Repeat 2 for the other 3 sides
- This should just leave Step 2 remaining. Put the flight controller on the underside of your desk, so that the top is facing the floor. Click the Calibrate Accelerometer button, and Step 2 should now turn blue.
Once you’re all blue, go ahead and click Save and Reboot. Also, get familiar with that button, you’ll undoubtedly be using it a lot. Any page that you change settings on that has a Save or Save and Reboot button, make sure to click it before you leave the page.
Time to build your plane
Now we have completed the parts of the iNav setup, which are better to do before installing the flight controller. You can now setup the flight controller in your plane and connect all your components. In the remainder of this guide, we will complete setting up iNav 3.0 with the flight controller in the plane. Also, I will cover setting up the GPS, and receiver. Other components will follow a similar path. All you have to do, is when you connect the component to the flight controller is make a note of the UART you have connected it to.
This guide is purely dealing with the iNav setup, not the installation of the components. But if you are using a Mateksys flight controller, they have great wiring diagrams for iNav. Just remember that with UARTs, you connect the Rx of the component to the Tx of the flight controller, and vice versa.
Continuing setting up iNav 3.0
On your flight controller, there will be a little arrow. See the image on the right. The way to keep setups the most simple is to have this pointing towards the front of your plane, and the top of the flight controller pointing towards the sky. However, this is not always possible. In which case you will need to change the board alignment to match how the flight controller sits in the model.
A simple, rotated flight controller
Most of the time, people simply rotate the flight controller 90 degrees to the let or right. This is usually to make access to the USB port, or pins easier. If that is the case for you, adjusting the board alignment is still very simple.
Head in to the Configuration page and find the Board and Sensor Alignment section. You will need to change the Yaw Degrees.
You can check that the alignment is correct on the Setup page. When you move the physical plane, the onscreen representation (could be a CleanFlight box or a 3D model of a flying wing. In iNav 3.1 it could also be a 3D model of a plane) should move in the same direction.
Setting up non-standard flight controller alignment in iNav 3.0
However, if you are an RC pilot who has chosen to install your flight controller at a completely different angle. You will now need to change the alignment in the CLI. There are three commands for setting the board alignment:
These all use 10ths of a degree (centidegrees) for setting the alignment, and have a range of -1800 to 3600. So if, for example, you needed to rotate the roll by 90 degrees. You would need to use the command
set align_board_roll = 900
Set your alignment and use the Setup page to check that it is correct.
Board level in flight
In older versions of iNav; we used to add some degrees to the pitch angle, to compensate for the angle of attack needed for level flight. In iNav 3.0 we do not do this. The board alignment settings are purely for making sure that iNav knows where the front and top of your plane is, in relation to the flight controller.
There is a new setting on the PID Tuning page, under the Mechanics tab, for Level Trim [deg]. We use this setting to set a base level for the angle of attack for level flight. Positive numbers always give a nose up attitude, negative numbers are nose down. This value can be set in flight using the new AUTO LEVEL mode.
Selecting the Ports
Next, we need to assign ports to all the ancillary devices connected to our flight controller. In the majority of cases, this is the Receiver and GPS. But can also include things like VTx control (SmartAudio/Tramp Telemetry), ESC telemetry, or many other options. This is a simple case of matching the UART number on the flight controller for each device to the port number on the Ports page. Different devices will appear in different columns, depending on their function.
There are a couple of important things that we need to be aware of on this page. These are pretty important parts of setting up iNav 3.0, which could potentially cause problems if you’re not careful. Firstly, never remove MSP from the USB VCP port. This is how your flight controller communicates with Configurator. If you remove this, your USB port will not work. It is also worth keeping MSP available on a spare UART. This means that if your USB port gets damaged; you can use that UART to connect to configurator via an an adaptor. Serial RX is the port that hosts your receiver. You should not set up anything else on that UART.
In the Telemetry, Sensors, and Peripherals columns, you see the port type followed by a number. This number is the baud rate for the port. In other words, the speed that it communicates with the device. In most cases, this can be left on AUTO, or the default setting. However, sometimes a manufacturer will give you a value to put here. I’d recommend trying it on AUTO or default first. If it doesn’t work, then set to the manufacturer’s rate.
Also, don’t forget to Save and Reboot when you’re done.
Setting up the Receiver
Once you have set the ports up. The next step it to check the receiver. Head in to the Receiver page. On the right is the Receiver Mode section. This is where you set up the type, protocol, and port settings for the receiver. You will need set this up for your specific receiver. When you set this correctly, you will see movement in the Channel Map on the left, when moving your gimbals.
The next part that you want to match up is the Channel Map. iNav defaults to AETR. However, if your transmitter uses a different channel order, you can just type it in to the box here. However, I’ve found it easier to just set the transmitter default to AETR.
Finally, we need to check that the bars are moving the correctly. Before we get started here, I would just like to remind you that there should only be a basic airplane mix in the transmitter. That is the sticks directly mapped to the output channels via the mixer. You should not do any advanced mixing like elevons or v-tails in the transmitter.
Now that we have everything in place, lets test. Move your pitch gimbal towards the top of the transmitter. The pitch bar on the receiver page should move to around 2000. If it doesn’t there are two potential issues.
The wrong bar moves
If the wrong bar moves, your channel order is wrong. So check that and get it working correctly. The other thing, could have been that you had a non-standard mix in the radio, but we covered that, right? You only have a pure airplane mix set up right?!!!
The bar moves the wrong way
This is the only time that you can reverse one of the 4 control channels in the radio. Reverse the channel so that the bar moves towards 2000 when pushed towards the top of the radio; and towards 1000 when pulled down towards the bottom of the radio.
Check the other three channels
Now the pitch is correct, lets check the roll. Move the roll stick all the way to the right. It should be sat around 2000. If not, you need to use the same procedure as above to get it moving the right way. Moving full right should be 2000, moving full left should be 1000.
Once the roll is good, repeat this for the throttle and yaw.
Now that all our controls are moving correctly, we need to get the endpoints and centre point right. If you move a stick up or right, you want it to be bang on 2000, or as close to it as possible. The stick down or left should be 1000. And stick centre should be 1500. To adjust this, you need to change the endpoints on your transmitter’s outputs. As most transmitters are different, I won’t cover this here. But if you use OpenTX, this video will help.
The next thing that we’ll be looking at while setting up iNav 3.0, is setting up the GPS. We should have done all the work for this by setting up the ports. This is really about some settings that can help out, and making sure that the GPS is working.
The first place to look is at the top of the page. There is a GPS status indicator. First remember to plug in the battery. Some flight controllers need this to provide power to the GPS. If this is blue, everything should be good. You can validate this on the GPS page. Check the Total Messages. If the number is increasing, the GPS is communicating with iNav correctly.
If it’s red, there is a communications problem. The first thing to check is that the UART is wired correctly: Rx to Tx and Tx to Rx. If that is good, then the problem could be with the port speed or GPS Protocol. So check with the GPS manufacturer for the correct protocol.
Optimising your settings
Once the GPS is working, there are a couple of settings that can potentially improve the GPS performance. The first, is if you use the UBLOX Protocol, you can try using UBLOX7. Another thing to set it to enable Galileo Satellites. If these satellites are not available, this will not have a negative effect on anything. But, if the satellites are visible, you will benefit.
One final improvement change is to the Ground Assistance Type. Unless you are travelling with the model all the time. It is beneficial to set this to your local area, as it will improve the altitude accuracy. The last, optional, settings are at the bottom. They are the settings for Timezone Offset and Automatic Daylight Savings Time. If you set these, the clock in iNav will be set correctly via GPS. Notice that the timezone offset it in minutes. So if you are in California, you will need to enter -480.
Adding some Modes
Where we are now in setting up iNav 3.0; we should have all our devices connected, and the receiver and GPS talking with the flight controller. This means that we can now set up some modes. At least enough to test our model on the bench. But while you’re here, you may as well set them all up. If you are already comfortable with your transmitter setup, I don’t really need to tell you what to do here. However, I would highly recommend having Manual, Acro, and Angle (or Horizon) set up in your modes. We will be using some of these to test the setup later on.
The INAV Fixed Wing Group OpenTX models
If you’re new to all of this, you may want to try out the INAV Fixed Wing Group OpenTX models. This is a great starting point, and will get you flying much quicker. If you don’t use OpenTX or would like to set up your own switch arrangement, I’m not going to cover that here. But, again, make sure that you have at least Manual, Acro, and Angle available.
Adding the mode ranges
In the image above, you can see the minimum setup to progress. The top mode is ARM. What this does is pretty self explanatory. Don’t worry if the box on the left doesn’t light up blue. The boxes will only change to blue if the flight controller can allow it to. This isn’t an indicator that the range will work or not; which to be honest, would be more useful. I’ve set this on channel 5, which is a two position switch on the transmitter.
After that, we have the three base flight modes: Angle, Acro, and Manual. I’ve set this on channel 6, which is a three position switch on my transmitter. I’m sure that with Angle and Manual, its pretty obvious as to where they’re set up. But Acro? Acro is the default flight mode in iNav, so there is no specific range for it. When channel 6 is in the middle position; neither Angle or Manual are selected. So that means the current flight mode is Acro.
When setting up iNav 3.0, you can add whatever modes you want here. But the recommended modes would include:
- Auto Level
- Auto Tune
Other modes that are useful are Position Hold and Cruise. With all these modes, you don’t need to combine them with any others. They all work on their own. Arm, should be on it’s own switch and channel. Also have Auto Level and Auto Tune on a separate channel and switch, so that you can activate them as necessary.
Setting the Mixer
The next stage in setting up iNav 3.0 is setting up the mixer. We have to select the correct mix for the plane we’re setting up. The first thing to set up is the Platform configuration. You should set this to Airplane, and I would recommend turning off Flaps, even if your model has them. This only enables the flaperons option on the modes page. But there are better ways to set up flaps and flaperons in iNav.
For planes with elevons, you would pick the Flying Wing mixer. For traditional planes or V-tails, they have their own mixers. Select the correct mixer for your model and click Load and apply. Check the manual for your model. There may be throw suggestions that require the mix to be slightly altered. One thing to keep in mind is to make sure that the weight on a control surface totals 100%. For example, if the V-tail below needed more yaw throw than pitch I would start increasing the yaw to 55% while reducing the pitch to 45% This keeps servo 4 and servo 5 at 100% total weight each.
Lets get some Outputs
Before we can test the throws, we need to enable the servo outputs. You do this on the Outputs page. The top option is Enable motor and servo output. Make sure that you do not have a prop on your motor before enabling this option. While here, we will need to set the protocol for the ESC. For standard plane ESCs, you would use the Standard setting. However, with other ESCs there are other options like DSHOT. With planes, there’s no reason to use any DSHOT higher than DSHOT150. In fact, if you have anything other than short cable runs to your ESC; you should not use higher than DSHOT150 as the faster protocols are more susceptible to noise.
Once you have set up those settings, you can now plug in your battery. Now your servos should move, and you should be able to spin the motor using the slider on the outputs page. Again, please do this without a prop on the motor. To enable the motor output for this test, you need to toggle the switch to show that you understand the risks.
At this point, you may be tempted to flick the arm switch, and use the throttle on the transmitter to test the motor. What you’ll most likely find is that nothing will happen. The flight controller will block the arming. You don’t need to try this at all. If the throttle is moving on the receiver page, and the motor spins correctly using the slider on the outputs page, it will work absolutely fine.
However, if this is one of your first times setting up iNav of any version, not just 3.0, you may not trust this yet. So we can perform a simple override to test. Lower the throttle, then toggle the arm switch about 10 times, ending in the arm position. You should then see the Motor Arming icon at the top turn yellow, which means the motors are live. The throttle should then control the motor.
Failsafe and RTH
The failsafe settings
One of the most useful features is the RTH on failsafe. So it would be silly setting up iNav 3.0 and not covering this. What this will do is: if you lose control signal with the plane, it will fly back to you and loiter at home or “land”. There are a few different options which we can look at soon.
The first thing that you want to do is head to the Failsafe page. There’s only one thing we need to do here, and that it set the Failsafe Procedure to RTH. Then click that Save and Reboot button. Next, go to the Advanced Tuning page.
Testing the failsafe
Seeing as we are here, now is as good a time as any to test the failsafe. An essential part of setting up iNav 3.0 is making sure failsafe will work. Make sure that your transmitter is turned on and on the correct model, and that your receiver has power. At the top, centre of the screen the parachute icon should be grey. This shows that the Rx connection is working. Next, power off your transmitter. The parachute icon should now turn red, indicating Rx loss and entry in to failsafe mode. Switch your transmitter back on, and the parachute should once again be grey. If this has worked as described, all is good. However, if this is not the case. You will need to look at the failsafe setup on your receiver. For FrSky you should set the failsafe mode to Hold or No Pulses. With Crossfire, it should be set to Cut. Other systems will need setting up differently.
Configuring the RTH
As mentioned earlier, the RTH settings are set up on the Advanced Tuning page. This page has changes a fair amount in iNav 3.0. Once loaded, scroll down to the Generic Settings section. There you will find RTH Settings. At this point, I’m going to direct you to the iNav Wiki. I have separated out the Return To Home settings to a separate page. This covers how all the different RTH modes work, and now how the different Climb First settings work. So it would be well worth having a read of this before continuing. It will open in a new tab, so you will not lose where you are here.
Here are my basic RTH settings. I’m not recommending people copy these. You need to set the RTH settings need for your flying area. Most of this is covered in iNav Wiki document above. But, I’ll mention a few things here.
RTH altitude mode will be set based on the area you are flying in. AT_LEAST_LINEAR_DESCENT will work well in most standard situations. But if you’re flying around hills or mountains, MAX would be a better option.
RTH Home altitude is a useful setting, as if your RTH altitude mode has the potential to have your model quite high when it reaches home. This setting will loiter the model down to the altitude set here. I set mine so that it is above obstacles, such as trees, at my home location.
Climb before RTH is something that is very specific to your flying environment.
- Turning first (Climb before OFF) would be the most efficient RTH climb mode, as you are climbing on the way home. However, some times turning first could result in you ending up in a tree.
- If you like flying low, there is more chance of obstacles to the side of you, as you are more likely flying towards a gap or open space. This is why mine is set with climb first on. This does mean that it is a less efficient method, as there is 50% chance you could be flying away from you; so are using energy to climb while still heading away.
- The last option, and new to iNav 3.0, is a spiral climb first. This sees you loiter up to altitude. It is useful in hilly areas, where yo could potentially have terrain obstacles in any direction, so need to get up to altitude before returning.
The last thing that I’m going to mention is Land after RTH. iNav does have a “land” feature for fixed wing. Though in essence it is really a controlled crash. I used to have this set to NEVER. But, with the new Safehomes feature (2.6), I have set a safehome to be used with only failsafes. I have also set Land after RTH to FS_ONLY. Regardless, I would only use the land feature in an emergency, and on an area of open, flat ground.
Setting up OSDs
I’m not going to cover OSDs too much, as I believe they are a personal thing and most pilots’ OSD layouts evolve over time. But there is more to discuss here than just layouts. There are also a few things that will be helpful for people who are setting up iNav 3.0 for the first time.
The first thing that I’m going to mention may come as a surprise, as it seems to be adding complexity. But in reality, it can be very useful, and actually make things easier to find. That is multiple OSD layouts.
Multiple OSD layouts
So why is this useful? As I mentioned, it can make things easier to find. The reason for this is that we can de-clutter the OSD. Sometimes people fly around with a load of information that they don’t need all the time. So why not make it optional?
Above you can see my current OSD layouts. I actually have 5 OSD positions on my S1 potentiometer. They are: Default Layout, OSD ALT 1, OSD ALT 2, OSD OFF, and OSD ALT 3. On the right you can see my setup on the modes page. So I have a lot of data that reduces, until there is not OSD at all. After that I have the iNav tuning OSD.
Again, like the RTH settings, I’m not putting this here for you to copy, but more for inspiration. So here’s the thought behind my OSD layout. The default layout has got everything I need before launching, during a failsafe, or while testing things out. I don’t usually fly with this layout unless I’m testing something. ALT OSD 1 is my main flying OSD layout. It has the main flight information I need with an AHI. ALT OSD 2 reduces the information on screen further, and loses the AHI and side bars. This gives a great view of the sky with the basic information like altitude, speed, cell voltage, RSSI, and flight mode. The next turn of the knob has no OSD at all, just a wide open view. The final OSD layout is based on the INAV Fixed Wing Group’s Pro OpenTX model, for in flight tuning if needed.
Switching to the default layout in a failsafe
You only need to put your GPS coordinates or Plus Code on the default OSD. This is an extremely useful piece of information to have, but you only need it while in a failsafe situation. If you’re flying normally, and everything is good, why do you need your coordinates? If you have an issue, but still have an RC link, just switch to RTH. Setting this up is just entering a line in the CLI:
set osd_failsafe_switch_layout = ON
At the top of the right column, there are options for the video format. It is best to set this and your FPV camera to the same format.
Setting up your OSD
The process of setting up the OSD is pretty simple. Just turn features on or off in the list on the left of the screen. Then drag the elements to where you want them on the layout. Unfortunately, there is no way to copy layouts in the Configurator. On the right of the screen are options for the units (IMPERIAL, METRIC, and UK), the precision of some units, the sidebars, and crosshairs. Set these up to your preference. Below that are the alarms. You can set these to blink once the threshold is passed; or set them to 0 to disable the alarm. Last on the right are specific settings for the DJI HD OSD. iNav 3.0 has added extra workarounds for the DJI HD system. You can set these up in that section.
Other things to for your setup
Calibrating the current sensor
For initial setup and testing, the standard current sensor values provided by the flight controller or PDB manufacturer will be fine. But, if you need more accurate current readings, you can calibrate them using this guide.
Setting up iNav 3.0’s continuous servo autotrim
Continuous servo autotrim is a new feature in iNav 3.0 that does exactly what you would think. It trims the plane at all times, when you have no stick inputs, in all modes except manual. In flight, iNav stores the trims in the servo mid points. So, switching to manual uses the trims. iNav saves the trims when you disarm. To enable it, you go to the Configuration page and scroll to the bottom. It is in the settings boxes on the right.
I hope this guide got you comfortable with setting up iNav 3.0. Don’t forget I also have a useful iNav pre-maiden checklist that will help you too.
Original article at mrd-rc.com.