Many military drone types are equipped with engines, including fixed-wing, unmanned helicopters, and larger multirotor platforms. These engines may be piston-driven or rotary combustion engines, turboshaft, turbojet or turboprop types.
Engine selection may depend on a wide range of mission parameters and requirements, including takeoff weight, aircraft size, range, payload types, and stealth requirements.
SP-180 HF SRE Heavy Fuel hybrid wankel rotary engine for UAS by Sky Power International
Military drones often have to operate in a wide variety of environments all around the world and under a range of challenging conditions. Their engines therefore have to be engineered to be especially resilient to extremes of temperature, icing, dust and sand ingress, salt spray and more. They may also require reduced acoustic and thermal signatures in order to minimize the chance of detection by enemy forces.
Fuels & Hybrids
Military drone engines may run on a range of fuels, including gasoline, diesel, and heavy fuels such as Jet A1, JP-5 and JP-8. Heavy fuel operation is becoming more common as a requirement, as many armed forces operate a “one fuel” policy that mandates that all land vehicles, aircraft and equipment can run off the same fuel type, thus simplifying logistics.
Saito 120cc four-stroke UAV engine by Innoflight Technology
Piston Enginesare a long-proven technology and are relatively simple in terms of design. However, they can be relatively noisy and produce a lot of vibration, which can affect sensor performance in applications such as high-resolution ISR (intelligence, surveillance and reconnaissance).
Rotary Enginesare quieter, more compact and produce less vibration, but are more complex than piston-driven engines and require more maintenance.
Jet Engines have excellent thrust-to-weight ratios, and provide greater flight speeds and maximum altitudes than either piston-driven or rotary engines. However, they are extremely complex with a lot of individual components, and are thus expensive to manufacture and require specialized maintenance. They also require a lot of fuel to run, and are overall only suitable for larger military UAVs that can accommodate the space and weight.
