DJI O4 4" FlyfishRC Atlas 4 V2

By SebFPV on Sep 06, 2025

3  0  2

ATLAS – New version

After the disappointment of losing my FlyFishRC Volador 3.5" during a flight without GPS, I wanted to create a new build that I could really trust for both cruising and freestyle.

This new ATLAS weighs 167 grams and is the direct successor of my previous version.
I chose LANNC 1408 3800KV motors, which offer the right balance between agility and efficiency. The electronics are centered around a SpeedyBee F405 AIO flight controller, simple and lightweight, keeping the build compact and reliable.

The frame is still the Atlas 4 LR FPV, strong yet lightweight, now paired with Gemfan 4023-3 propellers for smooth and efficient performance. A GOKU GM10 Mini V3 GPS has also been added to make sure I never repeat the same mistake that cost me my previous quad.

Filters are tuned down to the minimum, and PIDs are pushed a little higher to make the quad sharp and responsive. With 4S 18650 Li-ion packs, the ATLAS combines efficiency, agility, and long flight times without giving up freestyle fun or video quality. I find the 4-inch format especially interesting for endurance and long range when flying with Li-ion packs, making it a perfect compromise between performance and efficiency.

To keep the current draw under control, I use the VBAT Sag Compensation feature at 100% in Betaflight 4.5, which helps avoid exceeding 36A at full throttle. I plan to upgrade soon to Betaflight 4.6 to continue optimizing the setup.

Photos

Part List

Frame

Atlas 4 LR FPV Frame (6 builds)
Flyfish-rc.com
$36.90

Flight Controller

SpeedyBee F405 AIO 40A Bluejay 25.5x25.5 3-6S Flight Controller (5 builds)
Speedybee.com
$55.99

Motors

Aliexpress.com
Aliexpress.com
$1,404.00

Propellers

GEMFAN Hurricane 4023 - 2mm - 4pcs (2 builds)
Drone-fpv-racer.com
See Site

FPV Camera

DJI O4 Air Unit
Flyfish-rc.com
$109.00

Receiver

SpeedyBee Nano 2.4G 2.4G-TCXO 915M ExpressLRS ELRS Receiver (3 builds)
Speedybee.com
$10.99

Batteries

INR-18650-P30B - Molicel (3 builds)
Molicel.com
See Site

3D Printed

Flyfish Atlas4 Folding Antenna/XT30 Mount & GEPRC-M10-NANO GPS Mount
Printables.com
See Site

Misc Parts

GOKU GM10 Mini V3 GPS (10 builds)
Flywoo.net
$17.99
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Discussion

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Union   25 days ago  

I am partway through building a Flywoo explorer lr4, I had not seen the Atlas until now. I wish I had spotted the Atlas earlier as I prefer it. I am also using the SpeedyBee AIO however it will not fit in the front on the explorer unless I rotate it 45deg so I've put it in the rear with my VTX at the front!
The camera mounts look better on the Flyfish and more room for the FC. Although the explorer frame is a little lighter.
You could have got away with a shorter frame (lighter) as you only need one stack but probably such a frame doesn't exist.
4S li-ion pack is very heavy how long flight time do you get?
Have you tried or thought about bi-blades?

SebFPV   20 days ago 

Why not rotate the FC 45 degrees on the Flywoo? I think it's a strange move to put an FC in the rear. The Flywoo is undoubtedly a good machine, and the assembled price is attractive, but I find it underpowered in 4s with the 2750 KV.
My 4s battery weighs 195g, which is heavy, but even with the power limitation, the quad is very enjoyable in freestyle and "on rails."
I manage to fly for over 23 minutes without freestyle or long-range (trying RTHs in the field, for example, but this is the maximum endurance flight).
My average flight time is 12-13 minutes in freestyle, over 15-16 minutes cruising with friends in airplanes, which sometimes represents over 9 km of distance traveled.

The funniest thing is that I also used 3s 18650 P30B batteries, which saves 45g on the battery. The drone consumes less power, and I achieve the same flight time while being a little more agile in freestyle. Both batteries work very well on this 4-inch drone.

On your Explorer, you can try different batteries; it's interesting to find what you like best.
Personally, I stick with 1404 3800KV because they are powerful and light. I adjust the "Vbat sag compensation" with automatic PID profiles depending on the battery so as not to exceed 36A under any circumstances (100%/4s, 25%/3s).

I tried the two-bladed ones on my first ATLAS, but from memory, the flight time wasn't really better, at the expense of more jello!

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