Hybrid concepts as ideal drive technology for commercial UAV use

3W-56i B2 HFE FI

Hybrid drives are familiar to most people from the automotive area where they’ve been used for years in private and community vehicles. However the hybrid drive is also moving ever more prominently into the focus of unmanned aviation where it brings interesting benefits for commercial usage. Conventional combustion engines play a decisive role here.

“In the past 12 months we’ve had a marked increase in the number of enquiries involving the use of hybrid drive technology”, confirms Karsten Schudt, Managing Director of 3W-International GmbH. The Hessian company is known for its Heavy Fuel (HF) petrol engines, which are built into conventionally powered UAVs. “However our combustion engines are used differently with hybrid drive technology in unmanned aviation. The electrical motor is used for start-up or slow driving in automotive technology. On the other hand the combustion engine takes over the air vehicle’s takeoff as well as its permanent energy supply. Thus it functions as a carried-along power station”, explains Schudt further.

Most enquiries for the use of hybrid technology arrive at 3W international from the area of vertical-takeoff UAVs. The combustion engine takes on the most varied tasks in these cases. For one thing, it can be used for vertical takeoff, in which high power is required depending on the area of application. In connection with a generator, the combustion engine is used as the power supply for the electrically driven rotors, which are attached around the flying body on arms and which move the flying object after takeoff. Moreover the combustion engine helps out when the energy stored in the carried-along batteries declines. The flying object’s flight duration as well as its range can be massively extended that way.

“Most enquiries relate to the commercial or civil use of UAVs”, confirms Schudt. Mostly vertical-takeoff aircraft come into use in these cases in order to conduct the most varied tasks such as photograph and film recording, surveying tasks, or transports. “The use of HF engines tends to zero in these areas, because there’s no need to use different fuels. Commercial tasks can be well planned and can thus be conducted with conventional petrol engines”, Schudt explains further.

In the past the engines had to be adapted to the selected generator for power generation. The use of other generators or starters in connection with the selected engine was thus no longer possible. In order to avoid this, 3W-International developed a new connection between engine and generator.

The new 4-cylinder engine is provided with a ring on the engine mounting plate, which can be adjusted to the diameter and length. Thus different generators and starters can be used. “The benefits here are obvious. Customers are more flexible in the selection of generators, because the engines can be adapted to them. This design concept will be incorporated step by step to our other type of engines”, says Peter Wintrich, Head of Engineering at 3W-International GmbH, describing the advantages.

Because the use of UAVs in civil aviation continues to increase, 3W-International also assumes a further increase in the number of enquiries about hybrid drive technology. Since the aircraft deployed there vary greatly in technical performance capability and size, the need exists for combustion engines of different sizes and performance capabilities. “We’re able to offer an engine for any application area due to our broad range of engines. Here we are able to actively support customers in the integration of the combustion engine into the flying body”, says Schudt in summary.


With over 30 years of experience in designing, manufacturing, and testing 2-stroke engines, 3W-Modellmotoren GmbH has developed and patented the newest generation of Heavy Fuel (HF) engines for the Unmanned Aerial Vehicle (UAV) industry.

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