A VTOL fixed-wing UAV must support both vertical takeoff and landing and fixed-wing cruise flight. Its propulsion system therefore needs to be configured according to the airframe layout, maximum takeoff weight, payload, and endurance requirements. Common configurations include separate lift and cruise propulsion, tilt-rotor systems, and tail-sitter designs. The required number of motors, propeller specifications, and transmission components vary between configurations.
The supporting materials can be divided into three main groups: core propulsion components, power supply and distribution components, and installation and connection hardware.
Core Propulsion Components
Motors or Engines
Electric VTOL fixed-wing UAVs commonly use brushless motors. In a separate lift-and-cruise configuration, the vertical lift motors provide thrust for takeoff, landing, and hovering, while the cruise motor provides forward thrust during fixed-wing flight. These motors operate under different load conditions and have different efficiency requirements, so they should be selected separately.
Some tilt-rotor and tail-sitter UAVs use the same propulsion units for vertical flight and forward flight. Motor selection should take into account maximum takeoff weight, required thrust, motor KV rating, operating voltage, propeller load, and cooling conditions. Manufacturers such as T-MOTOR offer motors and propulsion systems for different VTOL configurations.
Electronic Speed Controllers (ESCs)
An ESC receives control signals from the flight controller and regulates motor speed and power output. Selection criteria include operating voltage, continuous current, peak current, cooling requirements, and control signal compatibility. The ESC must be compatible with both the motor and battery.
During vertical takeoff and landing, the propulsion system may require high thrust. The ESC may also operate under sustained loads during hovering. Its selection should therefore consider actual current demand, cooling conditions, and overcurrent protection rather than relying only on the motor's rated power. Hobbywing, for example, offers ESC products for UAV applications. The appropriate model depends on the propulsion configuration.
Propellers
Propellers convert the mechanical power produced by the motor into thrust. In a separate lift-and-cruise configuration, the lift propellers and cruise propeller are usually selected for their respective operating conditions.
Lift propellers must provide sufficient thrust for takeoff and hovering. The cruise propeller needs to balance forward-flight speed, propulsion efficiency, and endurance. However, propeller diameter and pitch alone do not determine whether a propeller is suitable for a particular flight phase. Diameter, pitch, blade count, material stiffness, and operating speed must all be matched to the motor and airframe design.
Manufacturers such as APC offer propellers for fixed-wing and electric model aircraft. Selection should be based on the motor manufacturer's recommendations and available propeller performance data.
Power Supply and Distribution Components
Battery Pack
Fully electric VTOL fixed-wing UAVs commonly use lithium battery packs, including lithium-polymer (LiPo) and lithium-ion (Li-ion) batteries. Battery capacity, voltage, discharge rate, weight, and energy density all affect propulsion output and flight endurance.
The battery configuration should be selected according to the operating voltage and maximum current requirements of the motors and ESCs, as well as the required mission duration. Continuous discharge capability, temperature rise, and cell voltage consistency should also be considered. Brands such as Gens Ace offer batteries for UAVs and model aircraft, with specific products selected according to system requirements.
Power Distribution and Management Components
Power distribution boards, power modules, and wiring harnesses distribute battery power to the ESCs, motors, and onboard electronic equipment. Some systems also use power modules to monitor voltage, current, and power consumption and send this information to the flight controller.
Wire gauge, connectors, and protective components should be selected according to the current requirements of each device. This helps prevent wiring overload, poor electrical contact, and excessive voltage drop.
Fuel System and Transmission Components
VTOL fixed-wing UAVs using combustion engines or hybrid propulsion systems require fuel tanks, fuel lines, filters, and other fuel supply components suited to the engine type. Engines equipped with carburetors also require the appropriate carburetor and intake components.
If engine power is transmitted through a mechanical drive system, additional components may include reduction gears, drive shafts, couplings, or belt drives. The actual configuration depends on the engine and propulsion system. Not every gasoline-powered UAV requires all of these components.
Installation and Connection Hardware
Motor Mounts and Mounting Bases
Motor mounts secure the motor or engine and transfer operating loads to the airframe. They must provide sufficient stiffness and strength. Mounting holes, shaft alignment, and connection dimensions must match the propulsion unit and airframe structure.
Fasteners and Connecting Components
These include bolts, nuts, washers, locating pins, and other hardware used to secure motors, mounts, propellers, and transmission components. Material, dimensions, and locking methods should be selected according to vibration loads and operating conditions.
Vibration Isolation and Cooling Components
Some propulsion systems require vibration isolators, damping pads, or flexible mounting components to reduce the transmission of motor or engine vibration to the airframe and onboard equipment. Motor and ESC cooling must also be considered in relation to installation position, airflow, and continuous operating load.
Custom Machining Services from Hansheng Automation
Mechanical components used in VTOL fixed-wing UAV propulsion systems may include motor mounts, mounting brackets, adapter plates, shafts, and equipment housings. These parts often require custom dimensions to match the airframe structure and equipment interfaces.
Hansheng Automation provides CNC precision machining based on customer drawings, supporting both prototypes and small-batch production for UAV propulsion systems and related equipment.
