The Limback-550cc UAV Engine is a 548 cc, horizontally opposed, four-cylinder, two-stroke UAV engine rated at 37 kW (50 hp). Its air-cooled layout avoids liquid-cooling hardware, while the opposed cylinder arrangement is intended to reduce vibration and provide even power delivery. With a net weight of 21.7 kg and overall dimensions of 385 × 410 × 390 mm including the exhaust pipes, the engine is designed for compact integration into small- and medium-sized unmanned aircraft. It supports 95+ octane unleaded gasoline or 100LL Avgas mixed at 50:1 with full-synthetic two-stroke oil.
The engine incorporates a solid-state magneto ignition system, an aluminum-alloy crankcase, a built-up shrink-fit crankshaft using forged components, aluminum-alloy pistons, and aluminum-alloy cylinders with ceramic-coated inner walls. Its standard configuration includes a 24 V, 1300 W starter motor and starter gear, shielded ignition wiring, shock-absorber pads and connecting hardware, exhaust pipes, a 28 V, 1000 W generator with bracket components, and a regulated AC-DC power supply. Recommended propeller options are 30×25, 32×20, and 30×23, while the supplied technical data specifies a maximum takeoff weight of 230 kg.
| Displacement: | 548 cc |
| Overall dimensions: | 385 × 410 × 390 mm, including exhaust pipes |
| Net weight: | 21.7 kg |
| Diameter: | 66 mm |
| Stroke: | 40 mm |
| Power: | 37 kW |
| Power: | 50 hp |
| Maximum takeoff weight: | 230 kg |
| Recommended propeller: | 30×25, 32×20, 30×23 |
| Fuel and lubrication: | 95+ octane unleaded gasoline or 100LL Avgas with full-synthetic two-stroke oil at a 50:1 ratio |
| Ignition system: | Solid-state magneto ignition system |
| Firing order: | Opposed two-cylinder synchronous ignition, 180° interval |
| Crankcase: | Aluminum alloy, low-pressure cast, T6 |
| Crankshaft: | Built-up, shrink-fit forged components |
| Pistons: | Aluminum alloy with elliptical-section grinding, cylindrical contour machining, T6 treatment, hard-anodized crown, and phosphating |
| Cylinders: | Aluminum alloy with ceramic-coated inner walls |
| Spark plugs: | Spark plugs for two-stroke engines |
| Starter motor: | 24 V / 1300 W, with starter gear |
| Generator: | 28 V / 1000 W, including bracket components; stated weight 622 g |
| Standard configuration: | Shielded ignition wire, shock-absorber pads and connecting components, exhaust pipes, generator assembly, and regulated AC-DC power supply |
