Upcycling smartphones makes a lot of sense, especially since they contain so many components that remain useful long after their desirability as a smartphone has faded. In the case of [Mountain DS Lab], they opted to use an 8-year old Xiaomi Mi 8 phone to add long-range FPV video link and remote control functionality to an RC plane, using the phone’s LTE cellular connectivity.

The smartphone was bought used for $23, with the default Xiaomi ROM overwritten by LineageOS to get a more lightweight and up to date Android installation on it. From the video it’s clear that this phone has seen better days, with the glass back cracked and a few ugly lines running across the display. Fortunately all that is needed is the motherboard itself.

One gotcha here is that the OS checks for the display on boot and will time-out if it’s not present, potentially halting the process entirely. The workaround requires disabling the display in the device tree, which is done by modifying the boot.img file as explained in the video. Next a custom bracket for the motherboard was printed so that it could be fitted inside the target airplane.

To communicate with the avionics, a USB-to-UART adapter PCB was created with a CH340 IC on it. This was then connected together for an initial test, with the extended front camera being used as the FPV camera for the custom Android application. Using the controller via the remote LTE link worked with the flight controller, so next the airplane was assembled for initial testing.

From this point it’s all pretty standard RC airplane assembly and testing, just with the typical RF-based control and FPV link replaced with the LTE link. Unfortunately flying drones isn’t permitted in the immediate area where the creator lives, so only some taxiing was tried prior to its maiden flight at a local airstrip that will be featured in an upcoming video.

Naturally, this isn’t the first time that someone has tried this type of remote control, with the ongoing Russo-Ukraine war being a prime example of LTE-based remote control of drones. Although we do not advocate wiping out a third of a nation’s strategic bomber fleet with upcycled smartphones, ultimately this is the same technology and a good way to create an RC drone that can last more than the few kilometers eked out from a 2.4 GHz link or so. Just be prepared for the LTE link to add a few milliseconds of latency.

A helicopter blade uses a swash plate and a set of linkages to change the angle of the blades. Not only does it vary the collective pitch to increase or decrease thrust, but it varies each blade’s pitch throughout each rotation, letting it produce more lift on one side of the rotor. This presented a problem to [worked in theory] — he’s building an RC helicopter from scratch, and this mechanism added both complexity and weight. Instead, he started looking for a way to get around the problem.

There were two options to eliminate the linkages: a linkage-less swashplate design used in Black Hornet drones, and an under-actuated design using angled hinges to control the blade angle. [worked in theory] started with the Black Hornet design, which has the end of each blade run along the swashplate on wheels, while a central spring presses them down. Friction in the hinge and wheels proved too high, and it stopped responding at higher speeds. A second, lower-friction design seemed promising, but it still required actuators, and thus weight, to control the swashplate. [worked in theory] therefore moved on to the under-actuated approach. In this design, the blades are mounted on angled hinges — by varying the motor’s speed throughout each rotation, inertia causes the blades to swing backwards or forwards, changing their pitch.

[worked in theory] tested two such rotor designs: one with one hinge per rotor, and one with one hinge for both rotors. The design using a single hinge seemed less sensitive to friction, was more responsive in testing, and had a more linear control response, so he used that. To actually make the blades, [worked in theory] 3D printed them as flat blanks, then thermoformed them using printed molds. During testing, the blades needed weights added to pull them back toward the standard angle under constant rotation; fortunately, though, this had the side effect of damping out unwanted vibrations.

There’s still a long way to go before the helicopter’s finished, but this is quite an impressive start. This is the second under-actuated propeller we’ve seen recently, both inspired by [Tom Stanton]’s original design.

With the ESP32 series of microcontrollers having had hidden software-defined radio (SDR) facility revealed, we’re now moving on from the announcement into projects making use of the finding. [Twotoz] has one using an ESP32-C5, to receive and demodulate analog FM video.

You might think that video is something which has largely gone away in 2026, with TV transmissions having made the switch more than a decade ago, and home entertainment appliances having used HDMI for longer. But it’s still very popular in the world of drones however, where it exists as 5 GHz FM transmission. There’s no digital cliff-edge to lose your picture if you fly into somewhere with bad propagation of radio waves, and perhaps more importantly, it has an extremely low latency. This receiver uses a Seeed Studio Xiao ESP32-C5 board with a simple resistor-ladder DAC to produce the video. It has a simple button channel interface, and a serial link for more in-depth options.

It’s good to see these projects appear, especially as this one’s 5 GHz and shows those chips work too with the hack. We’d be interested to know whether the latency of the SDR affects its usability though. You may be interested to know this isn’t the first time we’ve seen an SDR do video.

Thanks [Ink] for the tip!

Technically all that you need in order to make a drone fly is a single motor and single propeller, but realistically it becomes basically impossible to fly it at that point. In the case of helicopters you therefore need a second rotor somewhere to provide counterbalance to the first and to be able to steer.

There are of course a number of ways to make a drone fly with a single helicopter, but the compromise usually is to use very large propellers, as well as other mechanisms that make for a very large drone. This wasn’t good enough for [Joshua Bird] who wanted to have a very small, single propeller drone.

Key to making it work is not only a very high RPM, but also a hinged propeller hub that manipulates the  angle of the blades in such a way that both pitch and roll can be controlled if you react quickly enough. This turned out to be impossible using standard motor ESCs that do not directly measure the motor’s speed and position but rely on back EMF.

In the final prototype of the drone such details had to be measured directly, with super-fast adjustments to the motor’s speed only possible with custom controller code and a lot of trial and error. Even then the drone would often lose track of its position and crash once more. The solution there was to add an infrared beacon in the room and a sensor on the drone, to give it a fixed reference point.

You can find the project files so far on the GitHub project page, with upcoming changes to the drone design involving improvements like adding a scanner to the drone so that it can autonomously use features in its environment as fixed reference points. That way it might conceivably be able to fly outside as well, which would be quite exciting to see.

America’s mad scientists all have one dream: DARPA money. DARPA, the Defense Advanced Research Projects Agency, regularly throws round sweet, sweet tax dollars to push the envelope on any number of things, leading to such spinoffs as the very network carrying these words to you. Not every DARPA project ends in revolution though– like the latest DARPA Lift Challenge, whose goal was to see the creation of a vehicle that could perform Vertical Take Off And Landing with a payload 4x its own weight. We’ve embedded the ‘look back’ video below.

We hoped for something revolutionary, something bizzare, something really, really cool– and there were absolutely entries on the field that met all of those superlatives. Unfortunately, sometimes conventional designs are the convention for a reason , and the overall winner by AVIDrone, Inc. was just a very well made electric helicopter. One big lift rotor, one little tail rotor– aside from clever details in the solid-state batteries and carbon-fiber construction, it is a totally normal aircraft… albeit one that could lift 3.84x its dry weight, or 112 lb of payload. Interestingly a battery-powered hexrotor drone took home second place with a 3.64:1 lift ratio. Perhaps the big shock was not seeing combustion engines until third place: another helicopter, this time with a turbine engine. So much for energy density!

Some of the other more bizzare– if less performant–entries did get prizes to further their development, so we’ll likely see them back for the 2028 version of the challenge. Some of the concepts visible were covered here on Hackaday, like turning the drone body into a giant lift rotor , so perhaps one of you will have the bright idea that brings home a million in the next round of the contest.