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As fixed-wing UAVs are increasingly used for aerial mapping, surveying, inspection, environmental monitoring, and long-endurance missions, propulsion requirements are shifting from simply achieving high peak thrust to achieving a better balance between takeoff power, cruise efficiency, stability, and endurance.
For a 13-inch fixed-wing UAV, the propulsion system must provide sufficient thrust during takeoff and climb while remaining efficient during long periods of cruise operation. Unlike a multirotor, which continuously needs to generate enough thrust to support its entire weight, a fixed-wing aircraft relies primarily on aerodynamic lift once it reaches cruising speed. Therefore, the motor does not need to operate continuously at maximum output; instead, it needs to provide strong initial acceleration and reliable climb performance while maintaining an efficient operating range during cruise.
In this project, the BOGONG SUN 4320 350KV outer-rotor brushless motor was selected as a propulsion solution for a 13-inch fixed-wing UAV platform. With a 4320 motor architecture, 350KV winding, and high-torque outer-rotor design, the motor is intended to work with a relatively large propeller while providing the power and controllability required by medium-sized fixed-wing UAVs.
The objective was not simply to maximize thrust, but to build a propulsion system that could maintain a practical balance between propeller size, motor torque, electrical efficiency, aircraft weight, and flight endurance.
A fixed-wing UAV must overcome its own weight and aerodynamic drag during takeoff and climb. If the propulsion system is undersized, the aircraft may require a longer runway or launch distance and may have insufficient climb performance after takeoff.
However, installing an excessively large motor creates another problem: additional motor weight increases the aircraft's overall mass, which in turn increases the power required for flight.
The challenge is therefore to find a motor that provides enough thrust and torque without unnecessarily increasing the propulsion system's weight.
Propeller selection directly affects motor load, RPM, current consumption, and thrust. A 13-inch propeller can provide useful aerodynamic efficiency for a fixed-wing platform, but it also places a significant torque demand on the motor.
A 350KV motor provides a relatively low-speed, high-torque operating characteristic compared with higher-KV motors. This makes the 4320-350KV platform suitable for applications where a larger propeller is preferred and where the propulsion system needs to balance thrust with efficient power delivery.
The propeller, battery voltage, ESC, and motor must therefore be selected as a complete propulsion system rather than as independent components.
For surveying, mapping, inspection, and other professional UAV applications, the motor may operate for extended periods rather than only during short bursts.
Continuous operation places greater emphasis on bearing quality, winding insulation, rotor balance, thermal management, and mechanical stability. Excessive vibration can also affect the aircraft's flight controller, sensors, camera systems, and overall flight stability.
This means that a professional fixed-wing motor must deliver not only high output, but also consistent mechanical and electrical performance throughout the mission.
To address these requirements, BOGONG SUN developed the 4320 350KV outer-rotor brushless motor as a high-torque propulsion option for UAV platforms using larger propellers.
The motor adopts a 12N14P configuration and a 350KV winding, providing a combination of torque output and controllable RPM suitable for 13-inch-class propulsion systems. The current product specification supports 7S–9S LiPo battery configurations, with a listed peak current of up to 79.8A and maximum tested thrust of approximately 7.90kg under the specified test conditions. The motor weighs approximately 340g including the cable.
The outer-rotor structure places the rotating mass around the stator, allowing the motor to generate strong torque within a compact propulsion package.
For a 13-inch fixed-wing propeller, this torque characteristic is particularly important because the motor needs to accelerate and continuously drive a relatively large propeller without relying on excessively high rotational speed.
Instead of pursuing RPM alone, the 4320 350KV motor focuses on delivering usable torque across the operating range, helping the fixed-wing platform achieve stronger takeoff response while maintaining a more practical cruise operating point.
The 350KV specification is an important part of the system design.
For fixed-wing UAVs using larger propellers, excessively high KV can push the motor toward higher RPM and potentially increase electrical loading when paired with a large propeller. A lower-KV configuration allows the propulsion system to work with a larger propeller at a more controlled rotational speed.
For this reason, the 4320 350KV configuration can be considered when the design objective is to balance:
Takeoff thrust → Climb performance → Cruise efficiency → Flight endurance
The final KV, battery voltage, propeller pitch, and ESC configuration should still be validated according to the actual aircraft weight and mission profile.
Fixed-wing UAVs frequently carry cameras, mapping equipment, communication systems, or other sensitive payloads. Excessive propulsion vibration can therefore become a system-level problem rather than simply a motor issue.
The BOGONG SUN 4320 platform incorporates dynamic balancing requirements into its manufacturing process, with the current product specification listing a dynamic balance standard of P ≤ 5mg. The motor also uses copper winding with a specified 200°C grade, supporting stable operation under demanding electrical and thermal conditions.
For fixed-wing applications, these details are important because propulsion smoothness contributes to more than motor life—it can also help reduce unwanted vibration transmitted to the aircraft structure and onboard equipment.
For a 13-inch fixed-wing UAV, motor selection is ultimately a balance between thrust, torque, efficiency, weight, stability, and endurance.
The BOGONG SUN 4320 350KV outer-rotor brushless motor provides a high-torque propulsion option for UAV platforms that require a larger propeller and reliable power output. With its 12N14P configuration, 350KV winding, 7S–9S voltage compatibility, dynamic balancing requirements, and application-oriented customization capability, the motor can be evaluated for fixed-wing UAVs used in surveying, mapping, inspection, aerial photography, and other professional applications.
More importantly, BOGONG SUN does not approach UAV propulsion as a simple “motor selection” problem. By combining motor development, propulsion matching, sample testing, customization, and after-sales technical support, the objective is to help UAV manufacturers build a propulsion system that performs reliably from takeoff to cruise and from prototype testing to long-term operation.
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