A custom-built drone stunned the endurance community recently after staying in the air for more than 3.5 hours on a single battery charge. 

The milestone flight, completed recently by engineer and drone specialist Luke Maximo Bell, highlights how careful design and energy optimisation can dramatically extend flight times.

Bell is no stranger to records. In 2022, he set a global speed record with his Peregrine quadcopters. This time, he shifted focus from speed to stamina. 

The result was a machine built with one goal in mind: remain airborne as long as possible without recharging. 

 

Engineering for maximum air time

Bell approached the project with endurance as the top priority. Every design choice supported that single objective. Instead of using smaller, fast-spinning propellers, he selected large 40in carbon fibre propellers from T-Motor. These G40 propellers spin slowly on low-KV motors, which reduces power consumption.

He paired them with MN105 V2 Antigravity motors rated at 90KV. These were the lightest motors capable of turning propellers of that size without adding unnecessary weight. Larger propellers moving at lower speeds generate lift more efficiently, allowing the drone to hover with less energy.

Power comes from Tattu semi-solid state NMC lithium-polymer battery packs. These batteries deliver about 320 watt-hours per kilogram. That is roughly double the energy density of standard lithium-polymer cells. For long-endurance drones, higher energy density directly translates into longer flight times. 

Bell also trimmed excess weight from the batteries. He removed 180 grams, of packaging from each pack. He then replaced heavy connectors with lighter ones. In total, he saved 360 grams. That weight savings is close to the mass of the entire carbon fibre frame.

Luke Maximo Bell’s custom drone shatters endurance expectations. Image: Luke Maximo Bell/YouTube.

During hover, the drone consumes about 400 watts. When moving forward gradually, airflow improves, lift and power draw drop to about 250 watts. That efficiency gain played a key role in extending total flight time.

Fine-tuning the frame and wiring

Arm length became another critical factor. Bell used computational fluid dynamics simulations through AirShaper to test different configurations. He ultimately selected an 800 millimetre arm length, as the best balance between performance and weight. 

If the arms are too short, propeller wakes interfere with each other. If too long, the frame becomes heavier and less efficient. The chosen length minimised interference while avoiding excess structure.

Wiring also received close attention. Each motor required about 11 metres, of wire. Bell selected 18 AWG wire after calculating the trade-off between electrical resistance and added copper weight. Thicker wire reduces resistance losses but increases mass. He optimised for overall energy efficiency.

The frame uses carbon fibre tubes combined with 3D-printed arms, mounts, and landing legs. The structure is lightweight but strong enough to withstand long-duration flights. 

Streamlined electronics for reliability

To reduce failure points, Bell kept the electronics simple. A Holybro Nano Drive 4-in-1 electronic speed controller manages power. A TBS Lucid H7 flight controller runs INAV firmware. A Matek GPS module provides positioning data. A DJI O4 Air unit transmits live video back to the ground. 

Earlier lightweight components failed during testing. Bell replaced them with proven parts to improve reliability. Multiple bench tests measured thrust-to-power ratios under different loads. He found that efficiency decreases as thrust increases, which helped him maintain a lower weight while preserving adequate thrust margins.

Initial flights included oscillations and broken components. Each setback informed design improvements. After refining the system, the drone achieved a continuous flight of more than three hours and 30 minutes, even in windy conditions.

At two hours and 14 minutes, it had already exceeded SiFly’s hover benchmark with significant battery capacity remaining. Forward flight further improved efficiency. The drone landed safely with battery voltage at 2.95 volts to prevent damage. 

The endurance mark remains unofficial, but it clearly surpasses current known benchmarks.