AR741 single-rotor rotary surveillance UAV engine

The AR741 is a single-rotor Wankel-type spark-ignition engine from UAV Engines Ltd, developed for the propulsion of small surveillance-type unmanned aircraft. It derives from the maker's AR731 target-drone engine, and it has completed a 150-hour FAR-33-type endurance test.

The engine's displacement is 208 cc, and its maximum power output is 38 bhp (28.3 kW) at 7,800 rpm. Its mass is 10.7 kg (23.5 lb) without the generator, which gives the high power-to-weight ratio that the maker highlights. For an integrator, the figures define the size of airframe the engine fits: a surveillance UAV in the tactical class whose cruise power demand is well below the maximum rating.

Fuel consumption is 0.57 lb/bhp/hr at maximum power and 0.52 lb/bhp/hr at cruise. The engine runs on gasoline. These values allow endurance to be estimated from the fuel load and the cruise power. The rotary design has nominally zero radial vibration, although the peak instantaneous torque is four times the mean, a point to consider for the drive-train, the propeller and the payload mounting. The cross section is low, which helps with fuselage fairing.

Ignition is by an electronic contactless magneto with an RFI-suppressed high-tension system, a feature that limits interference with onboard radio equipment, navigation and payload sensors. The engine has provision for mounting a generator, either a GEC/Plessey 28 V unit or a 900 W or 1500 W alternative, so that the avionics and payload can be powered from the engine instead of a heavy battery.

The maker also offers engine integration and application support from its aerospace engineers, and its range covers engines for tactical UAVs, target drones and single-mission platforms.

Typical applications are surveillance and reconnaissance UAVs, tactical unmanned aircraft needing long endurance on a compact engine, and target drones that use closely related variants of the same engine family.