Review: Nirvana TX by UndergroundFPV and Flysky (Dark Knight)

by Oscar

I shared news about the Nirvana TX back in February, and it’s finally here! I will try to cover as much information I have in this review.

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Learn more about choosing radio for mini quad.

Where to Buy


The Nirvana is nicely packaged and protected by a removable hard plastic cover from knocking the sticks buttons and switches.

Accessories included are:

  • Two Flysky radio receivers
  • Stickers
  • 3.5mm trainer port cable (1.5m)
  • Micro USB cable (1m)
  • Instructions Manual
  • External JR module mount

Note that battery is not included.

Two Different Versions

The Nirvana TX (previously known as the Dark Knight) is designed by UndergroundFPV and manufactured by Flysky. There will be two different versions: the UndergroundFPV version, and the Flysky version.

As far as I know, the main differences will be the software that runs on these radios. The one we are reviewing is the UndergroundFPV version.

The UndergroundFPV version is better. Not only you can support the brains behind this product, you will also get the best OpenTX firmware.

A Closer Look at the Nirvana

The build quality of the Nirvana radio exceeded my expectation! I thought it was going to be tiny, but it’s actually a full size transmitter! Almost as big as the Taranis X9D as shown in the following picture, it feels really solid in the hands. The Nirvana weighs around 650g with batteries which is lighter than the X9D, but about the same as the Taranis QX7.

I am also impressed by the many thoughtful and practical design details, which I will cover throughout the review.

The metal hardware pieces are alloy 6061 (switch nuts, stickends, grips etc). They were originally blue in the rendered images, but changed to “rainbow color” in the production version.

According to UndergroundFPV, the color effect is achieved using electroplating anodising process. They did it in a way so that every piece of metal looks different, and every radio would be unique!


The NIrvana radio is equipped with digital hall sensor gimbals. The throw/travel of these gimbals is similar to the the Taranis. The springs are pretty loose and they don’t have much tension out of the box. Some people like it, some don’t. Anyway I will show you how to adjust it shortly.

It came pre-configured as Mode 2 (Throttle and Yaw on the left stick), you can also change it to Mode 1 quite easily. I’ve been told the easiest way is to unscrew the hall sensors and just swap the gimbals from left to right.

You can probably guess by the gaming console design, that it’s intended for “thumbers” – pilots who hold the sticks with only their thumbs.

Being a “pinchers” myself – who hold the sticks with index fingers and thumbs, it was pretty awkward at first. I’ve been using “box” style transmitters like the X9D for years and I am very used to the bigger body. After using it for a few days now, I think I am slowly getting used to it. I find it much easier to hold by putting my middle and ring fingers on the grips and rest the radio on the pinkies.

I really like the stickends, they are very grippy. The height of the sticks can be adjusted slightly, the longest stick is about 27mm, the shortest is about 20mm.

Switches and Pots

You have 4 switches on the front: top left is a 3-position, bottom left is a 2-position, top right is a momentary switch, bottom right is another 2-position. And there are also two rotary controls (potentiometers).

On the other side of the TX (underneath), we have another 4 switches: top left is a 3-position, bottom left is a momentary switch, and the switches are the same on the right.

The trim buttons are located under the potentiometers, right above the gimbals. You can tell the guys at UndergroundFPV didn’t design this radio just for the mini quad community, they also care about those who fly planes and wings!


The USB port is located on the top side of the TX, covered by a rubber cap. You can use it to charge the 18650 batteries inside the radio, as well as connecting to your computer to play with FPV simulators.

Next to the USB port we have the trainer port (3.5mm connector). You can hook it up to another transmitter for instruction/training purposes.

Many other radios have the connectors facing toward the user which can be inconvenient at times.


The antenna is foldable in the back of the TX, I think this is a fantastic idea. It prevents the antenna from damage during transportation. You can even use it as a stand! :)

There is a secondary PCB-style antenna inside the plastic case for diversity and some other cool features in the future.

External TX module

One selling point of the Nirvana is the support for external JR module including the Crossfire, Frsky XJT as well as other multi-protocol modules. Whatever that works with the Taranis X9D-Plus should be compatible with the Nirvana.

Before using external modules, you have to install the mount first. This design minimizes the size of the TX when you are not using an external module.

Here is how it looks like with the Crossfire Micro TX module installed.


The two “grips” on the back are great addition in my opinion. They make holding the radio more comfortable and secure.

If you don’t like the stock grips, you can easily remove them. I have been told there will be many more 3D print grip options released on thingiverse soon.

Micro SD card

I am pleasantly surprised that the Nirvana actually comes with a 2GB SD card, well done UndergroundFPV!

To access the micro SD card slot you first have to remove the Neck Strap holder.


The Nirvana takes two 18650 Li-ion batteries. The two batteries are connected in parallel, which means it can be powered by just 1 battery. Adding another increases the total capacity and run time. It even allows for battery hot-swap during flight! (when the TX is powered on)

You can charge battery through the USB port (connecting to PC or power bank). No need to take them out of the TX!

Check out my testing of which 18650 battery is the best for FPV Applications.


The color touch screen is another reason why I like this TX so much. The graphics and sound effect are so bloody awesome!

There is no need to use any physical buttons to operate the menu. You can point directly at the thing you want instead of going through all the options.


The Nirvana is using OpenTX firmware, a custom version that is designed specifically for this radio. It’s still being actively worked on, new updates are coming out constantly for bug fixes and new features such as “crashed drone locator”, “quad mode”, etc…

I will get into more detail when they release the stable version. At the moment it’s still quite buggy that’s why it’s delaying the shipping of the Dark Knight radio. Hopefully most of the major issues can be addressed in the coming days.

Adjusting Gimbals Tension

Here is how you can adjust the spring tension in the gimbals. You can also easily change transmitter modes.

Taking the Nirvana Apart!

What do I do when I get a new product? To take it apart of course :) Here are some closeup shots of the PCB’s.

Comparing to the X-Lite

Being another gaming console style TX, I am sure a lot of people will compare the Nirvana to the X-Lite. Luckily I recently reviewed the Frsky X-Lite so I can tell you what I think.

To be totally honest here, I think the Nirvana is a better radio than the X-Lite in nearly every way. Some people might prefer the smaller form factor and less radical design of the X-Lite, but that’s mostly a personal choice so let’s just focus on the performance and specs.

First of all, the Nirvana has full size gimbals, they feel just as good as the ones on the Taranis X9D, if not better. The X-Lite has much smaller gimbals and shorter stick travel. I would use the X-Lite if I need something tiny, but I wouldn’t use it for my everyday flying due to the lack of precision in control. The Nirvana feels more “pincher-friendly” than the X-Lite too.

Secondly, you can’t use standard JR module on the X-Lite without modifications. The X-Lite is designed for the smaller modules such as the R9M-Lite. Despite being pin-compatible with the Crossfire, you have to do some DIY mods for installation.

Lastly, the Nirvana uses 18650 batteries and they are rechargeable inside the radio. The X-Lite uses the less popular 18500, and you need a dedicated charger to charge them. In my opinion this is not user friendly at all.

Can I Use Frsky Receivers with the Nirvana?

I have been using the Taranis for years, and all my quads have Frsky receivers already. It’s going to cost a lot to replace them all with Flysky RX. If you are in the same situation, you can just get a Frsky XJT module for the Nirvana and carry on using those Frsky RX.

Two Stock Receivers

The Nirvana TX comes with two receivers to help you transfer over to the Flysky RC system, the Micro IA8X and IA8S.

The Micro IA8X is tiny – it’s about the size of an R-XSR and meant to be used on micro quads. The IA8S receiver has two antennas for diversity with IPEX connectors. However it’s a little bigger than the R-XSR or even XSR. Both are capable of iBus, SBUS and PPM.

The Micro IA8X has 600-800 meters of range, while the IA8S RX has 1Km to 1.5Km range.

I hope Flysky can provide smaller diversity receivers in the future, the iA8S is still a bit too big for mini quad IMO. We covered some other Flysky receiver options in this article.

A lot of people are going to use Crossfire or even the Frsky XJT so this might not an issue at all. Not to mention most TX these days don’t even come with any receivers, I shouldn’t complain really :)

Custom 3D Printed Grips (Dec 2018)

UndergroupFPV designed these grips for pinchers. They do feel slightly better, but the slots are a bit too tighter it feels a bit “complicated” to lock the fingers in. I’ve seen photos of different grip designs on Facebook, but not yet shared publicly hopefully we get to try more of these in the future.

Updating Nirvana Firmware (Dec 2018)

I wrote a guide on how to update the firmware on the Nirvana radio.

Update Sep 2019: Other Radio Options

The Nirvana still seems to suffer from bugs and slow OpenTX development after about a year. Support is also not very responsive based on feedback from customers in their Facebook group.

Maybe check out the Jumper T16 if you are a fan of OpenTX system and doesn’t want to get the Frsky radios and potential customer support issue from the Nirvana. The T16 is a more promising option IMO.

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Carlos Lega 28th October 2019 - 3:25 pm

PLEASE BE AWARE THAT UFPV SEEMS TO HAVE SERIOUS PROBLEMS!… I usually read Oscar’s posts (I found them very useful)… But this time I followed his recommendation to buy directly from UFPV and it seems I lost my money. I regret not reading further down, as there’s a warning here… But now is down, no one reply emails but (of course) they took my order and my money and haven’t shipped anything for more than month now.
Oscar: would you like to change the post about this recommendation?…

wayne 22nd October 2019 - 7:01 pm

This controller was dead on arrival. I managed to bind to both receivers however when I moved the gimbals the recievers could not pick up a signal so there is some fault in the controller. Also keep in mind that Frsky seem to be in total control of OpenTX (supposed to be open source but in my opinion hijacked by Frsky) and dictating what controllers OpenTX supports. As this controller comes from their competitors (Flysky) you will probably never see a release of software for the Nirvana. I purchased this from Banggood who have not responded to my refund request, when I tried to place a review on their website I just got a blank page, suspiciously all the reviews I see there are positive so I think they are deleting any negative reviews. I also tried to contact Flysky and support or warranties seem to be non existant. So save your money, I would really like the hardware if it worked.

Justin Gardner 22nd February 2019 - 3:04 pm

DO NOT BUY this from I have been waiting for 4 months and have only been contacted once over multiple attempts to contact and have been lied to. After some looking found that ,”It will ship later this week” is just a stock lie sent to anyone requesting shipping updates. Facebook pages have multiple similar reports from many users.

Kato 9th February 2019 - 3:38 pm

I know it *should* work with whichever external modules we use on Taranis radios, but just to double check, have you tried it with the R9M module?

I’m really on the fence between this and an x-lite, and JUST got the R9M receiver, so I’d probably get one of these if it’s definitely compatible.

Leigh Jackson 5th November 2018 - 10:17 pm

Hey, I would really love to see the same kind of latecy testing as you did for the X-lite here;

It was really cool how you found that OpenTX was adding latency through gymbal filtering. I would love to know the overall latency of this radio and how it compares

Dennis 3rd October 2018 - 3:53 pm

Yes it does. I have the Flysky version.

Tonny Hooijer 20th September 2018 - 7:54 am

Hello Oscar,
I’m curious about the voltage presented at the module bay. Because the irangex 4 in 1 modules is stated working in the 5v to 14V ….
Best regards,

Wolfdale 18th September 2018 - 1:13 pm

Hey Oscar, I wouldn’t recommend that XJT Frsky module. The IrangeX multi module is a much much better buy. It has the same output power (100mW), you get many protocols including Frsky and DSM2/DSMX, and it has a serial interface with the radio. The module you recommended uses PPM which as you know has a lot of latency.

Oscar 18th September 2018 - 6:23 pm

that’s actually a good idea, I haven’t tried the iRangX module yet but I shall give it a try!

ThomasCee 20th November 2018 - 6:20 am

That was related to my question… I have an old 72MHz JR radio with an XJT module, and I understand that that can go no faster than it’s native PPM latency speed. But what about a modern radio like this with an XJT? Does that also have PPM level latency? Or is that only with the original PPM 72MHz TXs from yesteryear?

Don 19th September 2018 - 2:07 pm

The main problem for me with this TX is the way it looks. To me it’s very ugly in a weird way I can’t explain. Function is great but come on, you got to have some aesthetics!
I ended up going for the X-lite and to be honest, after going back to a X9D for a bit, I really miss the smaller throw of the gimbals. Took a bit to get used to but now I miss it. Pinchers hate it and the Nirvana is better in all those ways. But in the end that’s just my opinion and lots of people will strongly disagree I’m sure.
Yeah I mean, why the hell doesn’t the X-lite come with a built in charger and why use the 18500 batteries?? I guess this is all because of small size and trying to fit everthingl in.
It will be interesting to see what the next few iterations will be with the X-lite.
But still, its small and compact and works for me.

Steve 14th September 2018 - 4:25 pm

Can you flash the flysky version with the ufpv firmware?

Oscar 18th September 2018 - 6:09 pm

I was told this is not possible right now, because they are different hardware revisions. But I am not sure for future batches.

Jason 16th November 2018 - 9:40 am

There is no differences in the hardware.

D Thomas 11th September 2018 - 5:33 pm

Does this Nirvana radio have mixing for slope wings and v-tail sailplanes. Great if i could use this radio for drones and fixed wing
Thank you

Paul Davis 12th September 2018 - 2:04 pm

It’s running OpenTX so will do everything the FrSky units do.

Daniel 3rd September 2018 - 12:51 am

I am quite sure, that there won’t be two versions. How should this be realizied? They have two different molds? They get thousands of Returns because people geht the wrong version? This would be a commercial suicide run… I bet this is a wrong Information.

onclefly 29th August 2018 - 6:52 am

Not Multi-Protocol this radio is no good !
So Multi-Protocol right now.

leeit2me 29th August 2018 - 2:00 am

i don’t own/care for opentx equipments.. but I do own flysky rx. can i bind my current flysky rx and go fly without waiting for the firmware to come out??

Daniil 28th August 2018 - 11:54 pm

I’m currently having an issue running a xjt frsky jr module. It does not want to bind. I’ve tried few things already such as as soon as i set xm+ to bind mode i would hold the white button on the jr module before turning on radio. Do i need to update to another firmware?

Ihunt4 10th December 2018 - 2:03 am

Did you ever fix the Frsky module issue?
I just got one and a tinyhawk and have the same issue, it will bind in the process but once I turn it all off and on again it’s like it never happened…
I’m on opentx 2.2.2

Greg Ryder 28th August 2018 - 5:29 pm

Hi Oscar, any chance this thing will ever be able to do 500mw on crossfire?

Oscar 9th September 2018 - 4:20 pm

Well, according to UndergroundFPV it’s limited to 100mW.

Enchilada Jones 18th September 2018 - 4:24 am

Does that include no 500mW if you externally power the Crossfire full size module?

RoNod 27th August 2018 - 11:51 am

Yeah, nextfpv vs flysky version! I’ve already preordered from nextfpv. How do I know which one? If it’s just firmware can I switch between?

Also, open-tx fw means there is no final version. You probably mean release version.

Oscar 28th August 2018 - 5:04 pm

The UndergroundFPV version has their logo on the bottom, Flysky version doesn’t.

Paul Pfau 26th August 2018 - 11:42 pm

In your gimbal adjustment picture, what does it mean -Trottle-add screw to remove spring? I’m supposed to move that screw to the other side?

Oscar 28th August 2018 - 5:03 pm

When you see the screw in that hole, it removes the spring in that axis and makes it the throttle stick.

vito Puopolo 26th August 2018 - 8:51 pm

Just wondering dose the nirvana support lua script for adjusting pids ect?

Oscar 28th August 2018 - 5:00 pm

Not yet but this is a feature they are trying to implement in the future.

LPB 26th August 2018 - 6:35 pm

Hey Oscar do you know anything about the differences between Flysky and UFpv versions? There is a lot of rumors around, but no real info… Wold be glad if you could tell the exact differences between the two versions

Alex S 15th October 2018 - 12:19 am

The Flysky version runs a normal OpenTx software while the UFPV runs a customized OpenTx software. The customized OpenTx (aka Open Underground) is supposed to have certain features already built in so you don’t have to add them and make it easier to set up new models. Currently Open Underground is still being worked on and many of the features they want to have are not available yet, but when its done, I’m sure it will be great.

8ANOS 26th May 2022 - 8:40 pm

As i want to upgrade 4 a quicker Micro SD Card..
Which is the Card Capacity Limit?