The HappyModel Larva X is the first thing I’ve flown that truly bridges the gap between full-size quads and the indoor mirco. It’s a craft that fits where others don’t, both literally and figuratively. But does filling a niche make it worth having? We gave this one a try courtesy of Banggood.

Specs

HappyModel Larva X, 3/4 viewThe Larva X is a 2.5-inch-class machine, spec’d with lightweight components. Some might call it a “toothpick” frame, but we’ll leave that definition to others. Here’s what makes it go:

  • Crazybee F4 Pro V3 Flight Controller with Betaflight OSD
  • 1103 7000KV Motors
  • 10A 4in1 ESC
  • 25–200mW 40-channel VTx with DVR
  • Runcam NANO2 Camera
  • Optional on-board or external receiver: DSM2/DSMX, FlySky, FrSky D8, FrSky XM+, FrSky R-XSR, or Crossfire
  • Runs on 2S or 3S, Recommended 300–450mAh
  • 2.5-inch props: EMAX AVAN Rush and/or HQProp 2.5×2.5×3

We’re looking at one with an external R-XSR. In the box you’ll get the fully assembled quad, a spare set of props, a spare canopy, some spare screws and nuts, a small cross-point screwdriver, a small 1.5mm hex wrench, and an instruction sheet. I also got the R-XSR’s printed manual sheet. The props on my quad were the EMAX AVAN, and the spare set were HQProps. Apparently there’s no guarantee that your props will be the same; it’s possible you’ll get two sets of one or the other.

We found HappyModel’s original Snapper6 to be pretty uninspiring, but they have been building reputation with their last few releases. The Mobula7 especially gained widespread acclaim. Brand-name parts like Runcam and EMAX / HQProp suggest a renewed commitment to quality.

Components

An F4 flight controller is definitely a standard at this point, as are Betaflight and an OSD. It would be a surprise to find otherwise. ESCs rated at 10A should be more than enough for these tiny motors and props. (My first 5in quad ran on 12A ESCs.) Motors are quite small at only 1103; that’s typical territory for a smaller 2S micro. They’re a bit lower Kv than you’d see on a micro, though. Paired with these smaller motors are pretty aggressive props. It’s nice that they make use of the screw mounts instead of just press onto the motor shafts. While this makes prop changes take much longer, it’s far more secure.

HappyModel Larva X bottom view

The belly of the beast.

The camera is a genuine Runcam Nano 2, which is excellent. It provides a really great picture in a variety of light scenarios that’s relatively free of noise. At 700TVL, pixelation in the image is more pronounced than with other cameras, but this doesn’t harm the flight experience. Light-to-dark transition is good, and low-light performance is also pretty good. Dynamic range is also good; there’s more detail in both highlights and shadows than any other micro-size camera I’ve used. The Nano 2 is sharpened more than most. From a picture quality perspective it’s just a bit harsh, but I found that it actually made flying a little easier and brought small details like branches into view more quickly. This version is customized specifically for the Larva X, which appears to be related to the connector on the back.

The video transmitter is easily adjusted via Smartaudio. It can be manually changed with an external button as well, but the channel indicators are buried in the stack and not easily visible. At least in a quick test, output power far exceeded the rated values. At the 25mW setting, I measured nearly 100mW, and at the 200mW setting I measured nearly 500mW! That’s a lot of power for a tiny VTx to be pumping out. It should mean a good consistent video signal, but some race directors might take issue. Another interesting feature is the built-in DVR. This lets you record interference-free video, but it’s still fairly low quality and only 25FPS. Remember to stop recording when landing since auto-save isn’t supported.

Build Quality

The assembly is acceptable. Soldering looks fine and I didn’t have pieces falling off in flight. The R-XSR is mounted well enough with antennas run at roughly 90-degrees and shrunk to zip-ties. It doesn’t look like you will have issues with any antenna getting chopped by the props. Though the FC is mounted very close to the frame, there’s an appropriate cutout so the USB port can be easily accessed. Everything seems mounted in a way that’s pretty stable.

HappyModel Larva X reeceiver mounting

Heat shrink doesn’t cover the tips of any antennas.

I definitely had a few gripes, too. Because the SD card slot on the VTx is in line with the props, it could be hard to get a card in. More importantly, there’s no protection on the SD slot, so you may find the card has ejected in a crash. The heat shrink on the VTx antenna covers only the larger sleeve, which creates a stress point where the antenna will eventually break. Heat shrink is similarly applied on the receiver antennas, so I would expect them to suffer the same fate. The battery strap is inadequate; it’s an inexpensive cable tie (the kind we recommend for securing balance leads) with low friction and too much length. Perhaps worst of all is the battery pad—the foam here is actually a piece of double-sided tape. You can remove the plastic cover to expose the adhesive.

The design is thin and spindly, which may not hold up too well in hard crashes. The FC is mounted tiny-whoop-style; the VTx and camera stacked on top with no real crash protection. Your stack will take the full force of a collision, and that could bring it to an early end. I’d have liked to see some better protection. The canopy isn’t going to help much in this regard; it mostly serves as a camera mount. At least it’s a variable angle, from zero up to about 30°.

Flight

I was concerned that this would be a poor substitute for a 3-inch quad. We’ve had a lot of fun racing the Helifar X140 and Diatone 349, but the seem to be the lower limit of that kind of performance. The reason I gave it a try was the weight—those two 3-inch quads weight in about 140g each; on my scale the Larva comes in at 52g (advertised at 49g). No battery is included with the quad, but I flew it primarily on BetaFPV 300mAh 3S, and GNB 300mAh 3S. These were both a good match for the craft with their low weight but high discharge capability.

A small city park with very low trees

Bobbing and weaving through these smaller trees was just about right for the Larva X.

On 3S, the Larva corners easily and is happy with many freestyle maneuvers. It’s zippy and easily controlled. Propwash isn’t much of an issue in normal flight, but if you try to bring it out intentionally it’s not too hard to do. The ‘comfort zone’ for this quad seems to be outdoors, but on the smaller side of typical. City parks with just one baseball field might be a good target, or a couple of suburban back yards shared by friendly neighbors. While it’s too much quad for most indoor use and not enough quad for long range or open-throttle speed runs, it’s just right to play over, under, and through the trees. You could certainly have a lot of fun racing the Larva if you could find others with similar machines. While I’ve been able to win races against 5-inch quads with a 3-inch, I don’t think the 2.5-inch Larva would be up to that task. It’s not as resistant to wind, either; a 15mph breeze causes instability that’s not a lot of fun.

On 2S, it starts to feel like an overburdened micro. New pilots might enjoy having a relatively tame quad, but almost any pilot with experience will want to run it on 3S. Flight times weren’t too bad on a 300mAh battery. It’s recommended up to 450mAh, which should give you a pretty decent flight length, though I didn’t have one available to test. Switching to the HQProps brought a smoother flight, but one that also lacked some power. I definitely had more confidence and enjoyed zipping around on the EMAX AVAN Rush props over the HQs. It was still a perfectly good flight and didn’t spoil the quad, but the AVANs seem to be a better match for the motors with this weight class.

Spare Parts and Modifications

HQProp and EMAX Avan Flow on a HappyModel Larva X

These two props look very different. Their flight performance tells the same story.

A number of the build failings can be remedied fairly quickly with some heat shrink. I recommend you re-shrink the receiver antennas and the VTx antenna. You’ll also want to visit the battery mounting: cutting the strap shorter is a good start. If you have leftover battery grip pad from a larger build, replacing the foam tape with it would be enough to keep these smaller batteries in place.

We’ve discussed the importance of having spare parts for drone modifications and ‘crash-proofing‘ like this before.  Definitely check out those articles if you need suggestions!

Getting spare parts for repairs shouldn’t be too much trouble, as most of the parts are sold individually.

HappyModel Larva X front view

Conclusion

Where 2-inch drones fly like “big micros” and 3-inch quads fly like “small 5-inchers”, the 2.5-inch HappyModel Larva X is really it’s own beast with a flight feel that’s not quite either. HappyModel has delivered a machine that really is fun to fly. It’s a great machine to break out where other quads might be too much or too little. The low weight and small size makes it more portable and less intimidating. However, if you plan to rip it especially hard, you might want to look for something a but more durable—the construction leaves important parts fairly exposed.

Whether it’s right for you depends on the kind of flying you like or want to do and the spaces you have available to do it. If you’re a hardcore racer, it’s not likely that the Larva will interest you unless racers in your area start a class of this specific size. And if all your flying is indoors, you’ll find the Larva a bit too large for most locations. There are a few situations where the Larva might be perfect: if you’re missing out on opportunities to fly because you don’t have enough space for your 5-inch, if there’s just a little too much foot traffic to be comfortable in your local park, or if you’re looking for something a little more tame but not quite so lethargic as most micros. If any of those sound familiar, then the HappyModel Larva X might be the right one for you.

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