FrSky X14S - a sport/competition radio with TW/Twin support

It's no exaggeration to say that FrSky have undergone a pretty dramatic transformation over the last few years. Having abandoned open source, they're now in full control of their destiny thanks to Ethos, their new and proprietary operating system. Their range of transmitters has grown, too, split between the Tandem (2.4GHz/900MHz) and Twin (2x2.4GHz) families. 

The TX14S is one of their more recent radios. With its compact dimensions and support for Twin, it appear - on paper at least - to be a good choice for soaring and electric flight. So, when FrSky offered me a unit to review I needed no persuading.

FrSky X14S

After a few weeks with the unit, has the X14S lived up to expectations? Read on and find out!

Full disclosure: FrSky provided the unit for me to keep. They have not imposed any conditions, sought any editorial input, or seen this review prior to publication. All views expresssed are my own.

X14: one radio, two variants

There are two versions of the X14: a basic version with 128MB of flash memory and regular gimbals; and an ’S’ version with 512MB of memory and CNC gimbals. The review unit is the ‘S’ version.

In the box

The X14S comes in a remarkably small box with the transmitter nestling in a plastic tray. Included are: 

• X14S transmitter
• Set of stickers
• QR code for the manual
• Neck strap

The neck strap is in two parts, connected by a quick release buckle. The idea is good: the lower part hooks on to the transmitter, while the upper part stays around your neck. Unfortunately the execution of the webbing is such that the strap cannot be lengthened or shortened, despite having the usual adjusters. An odd oversight.

Balance with a spare (adjustable!) neck strap is perfect, however.

X14S package contents

An ‘Eva’ case is available as an extra. 

No SD card is provided since model data is stored in internal memory by default. An SD card may be used if the internal memory is insufficient.

Styling and build quality

Styling is clean and functional. All the materials are high quality, and the fit and finish are good. The side grips are made of a rubberised plastic with a grippy, textured finish.

The basic shell feels comfortable in the hand, thanks to the thin profile and rounded edges. One nice feature is that the sticks are canted out very slightly for a more natural reach.

X14S and RM TX16S profiles compared

The T-shaped antenna is well anchored to the chassis, and doubles as a carrying handle.

Antenna doubles as carrying handle

Gimbals

The gimbals are CNC units with 10 ball bearings and a 4mm stick thread. Gimbal action is smooth with linear tension in all directions. 

So far so good... however, the stiffness of the springs was so high that I had difficulty reaching the end points. It's a personal thing, I know... but even with the tension reduced to the minimum - almost to the point of being slack at stick centre - the tension at the extremes was excessive, giving the stick a rather 'dead flesh' feel.

In short, the gimbals are crying out for softer springs, either factory fitted or as an alternative set. [edit: I have since replaced the springs, see postscript.]

Adjusting the tension

The first thing many users will want to do is adjust the spring tension or change between mode 1 or mode 2. In order to do either task, you first have to open the case. This involves undoing six screws and releasing a ribbon cable - only then do you get access to the adjustments. It's all a bit tiresome, especially when compared with other radios which provide external access to the adjusters.

Spring tension adjusters. Arrow shows socket for ribbon cable spanning front and rear shells.

Stick length

As a thumber with small to medium sized hands, I found the thumb movements to reach the end stops were excessive - even with the sticks screwed down to their shortest length. 

To make sure I wasn't imagining things, I decided to measure the thumb movements of various radios. The test involved screwing the stick tops down to the minimum, then measuring the end to end distance on the aileron axis, measured from the top of the stick.  Sure enough, the X14s came top of the list. Results as follows:

• X14S: 41 mm 
• X14S with custom printed stick ends: 39 mm 
• TX16S + AG01 gimbals: 38 mm
• X20: 37 mm
• X9D: 35 mm
• GX12:35 mm
• Zorro:33 mm
• TX12:33 mm
• Pocket:32 mm

While the RadioMaster TX16S also requires large thumb movements, this is mitigated by the softer feel and the location of the gimbal centre deeper inside the case.

Controls and switches

The X14 comes with all the knobs and switches needed for sailplane applications: 

• 1 x 2-position switch (right shoulder)
• 1 x momentary switch (left shoulder)
• 2 x pots (front top)
• 2 x sliders
• 4 x 3-pos switches (front top)
• 2 x momentary buttons (rear case)
• 4 x function switches (only one active at a time)

That's 16 in all - pretty good for a compact tx.

Auxiliary switches and controls

The switches are smooth acting with minimal lateral play - a step up in quality from those found in most open source radios. 

The momentary switch is located on the left shoulder, and will do as a DLG launch button (for right-handers). Swapping switches from one side to the other will be a simple soldering job. 

The sliders have a smooth action and with well defined centre detents. However, knobs S1 and S2 were very stiff with barely perceptible detents.

The horizontal trims are easy to reach. By contrast, the vertical trims are located quite high - thumbers will find them a bit of a stretch. 

The dials either side of the screen are the Ethos programming controls. The arrangement is well proven on the X18 and X20.

Function switches

Located above the screen are four configurable buttons designated FS1-4. These extend the functionality of the X14 without taking up much space. Each button incorporates a blue LED to indicate that it's on.

Function switches FS1-4

Each button can be configured as:

• a momentary switch
• a push-on/push-off switch. Each switch can be independent, or part of a group where only one switch is active. 

Switch and group states can be persistent between sessions. Unfortunately it's not possible to configure the state at startup, other than to set it to 'persistent'.

Function switch configuration menu

Potential uses for function switches:

• Motor arming, e.g. press two switches for n seconds.
• Selecting rates
• Selecting snapflap curves
• etc.

Screen and sound

The 2.95” TFT display has a resolution of 640 x 360 and is bright and crisp. It's not a touch screen, so all programming must be done using the physical controls.

Sound quality and volume from the speaker are adequate.

Ethos operating system

Ethos is FrSky’s proprietary operating system. It's designed from the ground up for touch, and it's highly flexible. 

A comprehensive ‘new model wizard’ will get you going quickly while for expert users there is a powerful free mix which can be used to build complete setups, much in the style of OpenTX. 

Note however that there's no equivalent to EdgeTX Companion for entering your setups - all programming must be done directly on the transmitter or via the simulator. A Companion style facility is promised as part of the Ethos Suite.

If you’re interested in learning more about Ethos, there are some links at the end of this article. 

External module

In order to expand the list of supported protocols, the X14 accepts external modules. If you buy one, make sure it's a 'Lite' type. (‘Nano’ modules, while similar to Lite devices, are not physically identical.)

'Lite' style modules are available from various manufacturers for ELRS, MPM, XJT and other protocols. FrSky themselves produce Lite modules under their Vantec brand, including a Twin Lite Pro module for radios without native support for Twin.

Note, however, that FrSky do not provide firmware or script support for ELRS or MPM modules regardless of manufacturer. Also, the configuration scripts must be Ethos-specific – Lua scripts for OpenTX or EdgeTX will not work with Ethos.

Battery

The review unit came with a 2600 mAh 2S LiIon pack. Inside the pack are two 18650 cells. One nice point is that the pack is sealed, so it should be more reliable that the usual battery box and individual cells provided with open source sets. 

The pack is a snug fit in the battery bay so there's no chance of the battery rattling around, but it also means there's no room for larger 21700 cells.

2600 mAh pack (2 x 18650 cells) 

Charging is via the USB port at the bottom of the radio. The same port is used for data transfer.

Bottom ports L to R: Smart Port, microSD, USB-C

RF module

The X14 is equipped with a TW-ISRM RF module. This supports Twin, ACCST D16 and ACCESS protocols. 

TW ('Twin'), is FrSky's newest protocol. It transmits using two transmission modes (FSK and LoRa) simultaneously on 2.4 GHz. Twin is already proving popular for sailplane application thanks to its excellent range.

GR6 receiver

FrSky also provided a TW GR6 receiver for review. This tiny unit incoprorates a vario sensor and should be ideal for DLG and other small models. It supports the Twin protocol only. 

TW GR6 receiver with built-in vario

The pins for CH6 lie along the case top. For models with 6 channels, a Y-lead is needed to share a servo output with the battery.

Auxiliary connector for S.Port/FBUS, S.Bus out and external voltage measurement

The auxiliary connector has pins for S.Port, S.Bus out, and FBUS. To drive FBUS servos the GR6FB variant should be used (no further information available at the time of writing).

For applications which require more than 6 channels, FrSky offer 8-channel versions, the TW G8 and TW GR8 (with vario).

Flight testing

For field testing, I flew my Sting slope racer with the X14S transmitter, GR6 receiver and six PWM servos. All controlled using my F3F template. The test session took place at Ivinghoe Beacon. 

F3F + X14S + GR6 at Ivinghoe Beacon! A happy combo :-)

It all went smoothly, though it did confirm my earlier findings regarding the stick ergonomics.

VFR (valid frame rate) was 100% for virtually the whole session, dipping very occasionally to 99%. Although the model was never further than a couple of hundred meters, it is a reassuring result.

Conclusion

There’s a lot to like about the X14 – the hardware and the Ethos operating system are top notch. The Twin protocol has excellent range and there's a good choice of glider-friendly receivers. 

Downsides? My main niggles concern the gimbals. Thumbers especially may find them too stiff (with the supplied springs), too long, and awkward to adjust. FrSky could do well to provide an alternative set of springs for those who prefer a regular feel. Details like the stiff knobs could also be improved. 

In conclusion: if you're in the market for a compact, robust and capable radio for soaring and electric flight then put the X14S on your short list... but try before you buy, particularly if you're a thumber.

Price at the time of writing is around £285 including 2600 mAh battery. If you're willing to forego the CNC gimbals and larger flash memory, the basic X14 is around £100 cheaper.

Postscripts

[25 August 2025] Those gimbal springs... I've finally replaced the (IMO) ridiculously stiff gimbal springs with a set of RadioMaster AG01/AG02 'hard' springs. These springs have 14 coils of thinner gauge material, but are otherwise identical in length and diameter to the X14 springs. In other words, they're a drop-in replacement. I'm glad to say that the RM springs have transformed the feel of the sticks - less force is needed to reach the extremes, while the centres are better defined. Note that RM also provide an alternative set of 'soft' springs with their AG gimbals - these have 18 coils. I tried these on the X14 too and, while they're usable, they are probably a bit too soft for most pilots.

[2 Jan 2025] I've printed some alternative stick ends. These minimise the height of the stick by avoiding the need for the locking screws at the tip. The result is a small but useful reduction in thumb movement and I look forward to trying these out on the field. 

The STL file is available from here.

3D printed short stick end

Specifications (X14S)

• Dimension: 192×193×72mm (L×W×H)
• Weight: 610g (Battery Excl.)
• Operating System: ETHOS
• Internal RF Module: TW-ISRM
• 2.95” Colour TFT Display Screen Resolution: 640×360
• Number of Channels: Up to 24 Channels
• Operating Voltage Range: 6.5V ~ 8.4V (2S Li-Battery)
• Operating Current: 330mA@7.4V (typ.)
• Operating Temperature: -10℃ ~ 60℃ (14℉~140℉)
• Built-in 512MB Flash Storage
• Battery Bay Size: 69.5×38.5×20mm (L×W×H)
• Data Transmission & Charging Interface: USB Type-C
• USB Adapter Voltage and Current: 5V+0.2V, ≥2.0A
• Compatibility: ACCST D16 / ACCESS / TW modes

Links

• FrSky
• Ethos Hangar - tutorials and glider templates
• Github - Ethos feedback community