Wankel engine Making a comeback in the UAS Industry and More

Wankel engine Making a comeback in the UAS Industry and More


With more than 35 years of experience in designing, manufacturing, and testing 2-stroke engines, 3W-International GmbH has developed and patented the newest generation of Heavy Fuel (HF) engines for the Unmanned Aerial System (UAS) industry.

The 3W-180 SRE hybrid is unique in the drive technology for UASs. The engine features 180cc displacement and a short-engine mass of 6.8 kg. A high-power version achieves 38.5 hp at 7500 rpm (rated power is 28 hp at 6000 rpm). A 5.66 hp/kg power-to-mass ratio with a consumption of 340 g/kW at full load results from this. The hybrid system, which feeds in 15kW for a time (e.g. 30 to 60 seconds) independently of the storage system’s capacity, is unique. This additional power can be drawn upon when starting a helicopter or during the acceleration of a fixed-wing aircraft.

“This hybrid system, as well as the very good power-to-mass ratio, opens up entirely new possibilities for us”, says Schudt. Since the engine isn’t sold as an individual engine, but instead only as a complete drive unit, a few projects are approaching completion at year’s end. “The engine must be adapted exactly to the UAS in order to optimally extract the former’s power. This time we’re working closely with our customers”, explains Schudt.


Engine 3W-180 SRE Hybrid
Type wankel rotary UAV engine
Capacity 180cc
Weight 6.80 kg/14.99 lbs
Weight with Generator 9.50 kg/20.94 lbs
Power 20KW/27.5HP @ 6000rpm
High Power Version 28KW/38.5HP @7500rpm
Hybrid-Boostpower add. 15KW
Max-Torque 32Nm @ 6000rpm / 36Nm @ 7500rpm
Power-to-Weight-Ratio 5.66HP/kg / 2.57HP/lbs
Fuel consumption 340g/kW @ max. load
Fuel Gasoline/Avgas
Kerosin (only with HPI injection)
Injection standard mainfold injection
HPI (high pressure) injection optional
Cooling Water cooled housing & Oil Rotor cooling
(activ cooling)


Its construction is compact with few moving parts.  The compact construction enables greater power density with light weight and modest space requirement. Displacement is smaller compared to other internal combustion engines. Nonetheless the Wankel engine offers high power and torque with very low-vibration engine operation. In contrast to the Otto engine, the Wankel engine consumes less fuel at high rotational velocity. It can be driven with both gasoline and Heavy Fuel (HF)

Manufacturers of unmanned helicopters contacted 3W-International in the months following the initial launch. “Specific requests are on the table and we assume that we’ll implement a few of them in 2018”, confirms Schudt. Helicopters in particular need high rotational speeds climb and hover.

The same is true for hovercraft. The Hessian engine builder also receives requests from this product segment. The engine was moreover in demand as a generator system for additional applications outside of the UAS industry. So for construction machinery, the intent is to use the Wankel engine as a generator to ensure the power supply when the actual drive motor isn’t being used. An additional new target group is thinking about deployment as a small, flexible generator unit on maneuvring areas, at large events, in civil protection, and on large construction sites. “We’re glad that the engine has a broad application spectrum and can be used in a multitude of vehicles. It doesn’t matter to us whether it finds application as a drive or as a power generator.

The engine is in demand both in military and civilian application areas. Noise emission has repeatedly been an aspect, especially in military applications. “Customers complain that noise reduction for Wankel engines is too involved. By reason of our own development possibilities, we’re able to develop silencers, among other things, for each engine that comply completely with our customers’ specifications”, says Schudt, describing the development portfolio. Observing silencer volume for the engine is particularly important here. “Otherwise the muffler diminishes the engine’s power”, continues Schudt.


The quality of 3W-engines stems from several factors. Technical expertise, long-term experience, tradition, and state-of-the-art production are the reasons for one of the highest quality levels in the industry. 3W is opposed to manufacturing abroad, so customers can be sure that every engine is of German quality.

From R&D, prototyping, purchasing, manufacturing, and calibration to on-time delivery, 3W guarantees constant and permanent quality control. Every manufacturing step is traceable. Employees are personally responsible for the fulfilment of 3W quality standards. Component suppliers and partners share these standards and guarantee these quality requirements.

3W International GmbH

Hollerstraße 12

61350 Bad Homburg, Germany



Phone: +49 (6172) 80 89 34-0


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