Featured The Market

Enhancing Unmanned Operations in Extreme Conditions with the Power of Two-Stroke

Peter Lietz, Head of International Business Development for Hirth Engines, explains why engine manufacturers must raise the endurance bar for unmanned aerial vehicles (UAVs) to advance capabilities in extreme weather conditions.

Drones have become a popular choice for various exploits, from hobbyist aerial photography to large organisations such as Amazon exploring the future of delivery services. In the same vein, governments, militaries and research groups are exploring the use of UAVs to enable highly effective monitoring of unforgiving terrains without risking manned aircraft or land-based patrols.

The need for unmanned aerial systems to navigate harsh environments is vital for the maritime, military and commercial sectors. Providing reliable and to the minute information on the status of, and threats to, environments like the Arctic is crucial as governments prepare to take action against significant issues such as climate change and increases in populations.

UAVs will play a crucial role in this future considering the need for operators to monitor harsh environments and difficult to reach terrains, especially rotary UAVs.

Reaching inhospitable locations can present a variety of logistical challenges, not least of which is the cost of sending land-based patrols or manned aircraft often from navy ships or other maritime vessels. This is where UAVs can enable operators to safely monitor terrains in a cost-effective and efficient way to better understand complex habitats.

Carrying out monitoring exercises in areas such as the Artic where there is a real risk to life can be a major challenge. Through the use of well-engineered rotary UAVs, organisations are able to perform a variety of tasks with ease. The responsibility to advance the endurance capabilities of UAVs falls on engine manufacturers. For this reason, we must continue to innovate to increase performance.

Over the last few years, rotary UAVs have grown in complexity, not only in terms of the platforms themselves but also the robustness and performance of the engines they run on. As the operational requirements for UAVs grows, engine manufacturers must continually innovate to improve power-to-weight ratios, reduce emissions, and accelerate capabilities in harsh environments.

For a long time, fixed-wing UAVs were considered the optimal choice for endurance and speed over their rotary counterparts. However, this is changing rapidly thanks to enhancements in engine design. Rotary UAVs are now becoming a platform of choice due to their reduced logistical footprint and the ability to take off and land in a confined or limited space, especially in maritime environments such as on-board navy ships and coastguard cutters for example.

The requirement for rotary UAVs to operate in extreme temperatures such as the cold of the Arctic or the severe heat of warmer climates is essential for operators. This is where two-stroke propulsion engines play a vital role. Two-stroke applications present rotary UAV manufacturers with a range of benefits, including ease of maintenance due to less moving parts and the ability to operate on heavy fuels which are a must for corrosive marine environments. Alongside this, two-stroke powered rotary UAVs are often capable of flying missions with a full payload in extreme conditions for more than five hours without overhaul.

With this as a backdrop, it is vital for UAV and engine manufacturers to accelerate the development of propulsion systems capable of operating in extreme locations around the globe. As the industry moves towards hybrid and electric propulsion new challenges will arise and it is crucial that OEMs raise the bar to power the next generation of UAVs.

In order to advance the endurance and capabilities of rotary UAVs, engine
manufactures must look to innovate the propulsion technology used. Electric is an increasingly popular option for commercial drones. However, electric comes with its own challenges and limitations, such as operational endurance and increased weight of the electrical motors. Considering the performance of batteries in extreme temperatures in comparison to their fuel-based counterparts, there is a long way to go before pure electric UAVs will be capable of flying extended missions in harsh terrains.

Hybrid applications that utilise both a combustion engine and electric propulsion systems will provide a bridge toward the future of pure electric flight. A clear advantage for hybrid applications is improving power to weight ratios to enable increased payload capacities. Hybrid UAV applications can be used in various functions, such as: electrically powered take-off and landing with conventional engines powering horizontal flight; or powering flight using only electrical motors whilst the combustion engine acts solely as a generator.

In addition, safety is a key purpose behind the pursuit of hybrid applications. For UAV manufacturers, having the ability to convert to an electric battery should the combustion engine fail could make all the difference in enabling a safe landing.

Operating UAVs in extreme weather conditions reduces the chances of potential health and safety issues associated with deploying staff or manned systems into harsh environments. In addition, a further key benefit of using UAVs is enabling the deployment of cost-effective systems that perform safely in extreme locations.

Ultimately, developing UAVs that can fly farther and for longer in harsh environments will require engine manufacturers to consider alternative fuel and power systems such as heavy fuel two-stroke applications. Heavy fuel is widely considered a must in the maritime industry when dealing with complex environments due to its resistance to extreme temperatures.

At Hirth, pairing a robust heavy fuel combustion engine with electrical propulsion is something we are pursuing to advance the future capabilities of unmanned systems and bridge the gap to pure electric flight.

For further information about Hirth’s portfolio of engines, visit:


About Hirth

Hirth Engines GmbH, based near Stuttgart, with global sales operated from Vienna, has a long pedigree in the development of propulsion systems, stretching back to The innovative company was founded by German aviation pioneer and World War I ace Helmuth Hirth, a student of US inventor Thomas Edison, and collaborator with the Wright Brothers and Zeppelin.

The company has set its sights on consolidating its leading role in the development of two-stroke engines for a range of diverse sectors including:
 Unmanned and manned light and experimental aircraft (fixed wing and
 Hovercraft
Next generation R&D will focus on hybrid engines, based on the company’s winning formula of providing easy to maintain power to weight ratio propulsion technology across civilian and military applications.

Similar Posts