Due to the growing number of inquiries concerning complete drive units for Unmanned Aerial Systems (UAS), the German manufacturer of 2-stroke and Wankel engines, Sky Power GmbH, has intensified its cooperation with Mejzlik Propeller from the Czech Republic. The objective is the development of propellers coordinated individually to the engine and the customer application.

“In past projects we were approached again and again by our customers for propeller recommendations. Since we develop complete drive units for our customers that are coordinated to the customer application, the requests on the part of the customers were understandable. Since we didn’t want to set up our own propeller development department, we looked around for a partner who had the same understanding of quality as us”, declared Karl Schudt, Managing Partner of Sky Power GmbH. Sky Power choses Mejzlik Propeller from the Czech Republic. “We had already worked well together in the past and were convinced of the quality of carbon fiber propellers”, elaborated Schudt.

In the world of unmanned aviation, Mejzlik Propeller is well known for its work. All propellers are manufactured from carbon fiber and can be adapted in a variety of features, forms and designs of the customer application and the outputs to be achieved. Besides the size and the pitch, the number of blades, the weight, the carbon fiber material as well as the surface can also be adapted. “The propeller must perfectly match the engine, as only this way can an efficient utilization of the entire drive unit be ensured”, explained Jan Hruška, Business Development Manager at Mejzlik Propeller.

Furthermore, at Mejzlik Propeller particular attention is paid to the quality. “Our customers sometimes move sums running into millions in the air, if one counts the UAS and the payload together. Apart from this, in future flying over groups of people will become routine. Flying must therefore be absolutely safe. For this reason, the quality of the propeller must be given special attention, in order to ensure safe flying”, stressed Hruška. That’s why various propeller tests are carried out before delivery. Besides a balance tests, an inner structure tests, an optional RPM tests and a visual quality inspection are performed.

Apart from that, for Sky Power there was a further incentive for the cooperation. Since every engine is coordinated to the customer specifications, so-called propeller curves are required. “Very few propeller manufacturers can provide these, as the tests are complex”, stated Schudt knowingly. The velocity, the flight altitude, the rotational speed as well as the environmental conditions influence the performance of a propeller and consequently also that of the entire propulsion unit. “Based on these details and the computation models, we can calculate and develop the right propeller for every application”. To design an appropriate propeller, we also consider the data that we already have from the propellers previously designed and measured. Based on these measurements and our experience, we can adapt the design to your requirements and give you a basic idea, how the respective propeller behaves”, confirmed Hruška. And Schudt added: “This experience is important for us, in order to provide our customers with a perfectly coordinated drive unit. Because this is what our customers expect”.

Both companies will in future work more closely together on customer projects.

“In individual projects, we will fall back on the experience of our Czech colleagues very early on, if our customers also want to adopt this approach”, stated Schudt. In this case the customer can expect a complete solution from a single source.

 

If you need more information or more propeller details, please contact the sales team.

3W-International’s performance partner Sky Power has also brought a new injection and ignition system to market, which can be used for all 3W gasoline and heavy fuel (HF) engines. The new systems are obtainable immediately. The conversion of engines already in use is also being offered. The objective was to massively reduce the engines’ consumption.

“The efficient use of UASs is becoming increasingly important for our customers. That’s why we as engine manufacturers are interested in a reduction of fuel consumption”, explains Karl Schudt, managing director of Sky Power GmbH. Exhaust, ambient air, and engine temperatures as well as air pressure can influence fuel consumption. So, these parameters must be permanently controlled to control the engine efficiently”, continues Schudt. “The optimization of engine management was therefore one of the new development’s goals.”

Sky Power’s new injection system for engines from 3W-International is called ECU030. The universally applicable electronic injection system is usable for both gasoline mixtures and HF applications. Four ignition channels with two separately settable injections nozzles ignite the fuel mixture. Pump pressure is controlled electronically here. A cold start function for the engine is also integrated. The automatic controller adjusts the fuel mixture to prevailing cylinder temperature, air pressure, and exterior temperature.
A PC can be used to monitor all engine data. The user interface is so intuitive that all of the engine’s settings and maintenance can be easily conducted. The CAN bus serves as communication. Actuation of the servo-motors and injection, the analysis, sensor signals (analogue and digital), general and manual diagnostic functions, and system updates can be controlled vial the CAN bus.

HKZ215, the new ignition system that Sky Power also developed at the same time, is likewise tuned to all of 3W-International’s engines. The new ignition can also be used for 2- and 4-stroke engines. Both systems are already being used today in the 3W-180 SRE hybrid Wankel engine from 3W-International introduced in 2017. The high-performance HKZ system was developed for significantly greater ignition powers. The engine’s overall fuel efficiency is thereby enhanced and the exhaust values improved. The HKZ is installed in a lightweight and rugged, nickel-plated aluminium housing. All the add-on components such as connector plugs and spark plug connectors are designed and shielded for challenging application areas.

“We are achieving better power performance in 3W engines with the new ignition and injection system”, Schudt explains. The test of a production engine from the 3W-110xi B2 TS FI series demonstrates this. The engine was tested with two different trial constructions having the same silencer L70 aluminium and the same 24×14 dual-blade propeller. In the first trial, the engine ran with the conventional ECU and ignition from 3W-International. These were exchanged for the ECU030 and HKZ215 in the second trial. In the process, a fuel reduction of up to 28% at 5500 rpm resulted. Even reductions of up to 69% could be demonstrated in the lower rotational-speed ranges. “The results aloft also surprised us, but they clearly show what is possible in the area of efficient fuel management”, according to Schudt.

In addition to the injection and ignition, the intake body was also optimized on the cylinders. The engine’s power density is greater thanks to the now better cylinder filling. The engine generates fewer harmful exhaust components and can be better controlled in different engine states. The improved combustion furthermore creates fewer residues in the engine, leading to a reduction in maintenance intervals. Moreover, the engine can be integrated into the aircraft independently of position, leading to optimum integration and weight distribution.

“The new ignition and injection system is obtainable for all of 3W-International’s gasoline and HF engines. We are also offering to convert drive systems already in use on the market. For this purpose, the engine has to be sent in to our service centre in Germany. Conversion effort is engine dependent”, explains Schudt. At the moment, the new systems are usable for the 110 ccm engine. Additional engines will follow in future. “The goal is to offer the ECU030 and HKZ ignition system for all of 3W-International’s 2-stroke engines”, according to Schudt.