Jet Retrofit for the LS8

M&D Flugzeugbau has been around since 1995. Since 2012, its in-house developed MD-TJ42 turbine has been used in sailplanes from Jonker Sailplanes. Over 250 of these jet engines are now flying worldwide. M&D has used this extensive know-how to implement retrofits. Now, for the LS8 as well. We spoke with Keno Markwald, now COO at M&D, about this exciting innovation.

Hello Keno! What is the key feature of the jet retrofit compared to other systems?

The key feature is clearly the weight-to-range ratio, combined with simple operation. The installation weight of the entire jet system is only about 13 kg. This is a huge advantage over battery systems, which can quickly reach a high installation weight, or conventional combustion engine systems, which have a higher risk of failure and more complex operation.

How flexible is the range?

The range is variably selectable, as it depends on the amount of fuel taken on board. With just 5 liters of fuel, you can gain approx. 700 meters of altitude, which is usually enough to reach an airfield. If you fill the tank with 60 liters, ranges of 350 to 400 km are possible. The pilot thus has a wide range to suit all flight and weight requirements.

How is this range achieved?

We predict a climb performance of 2.7 m/s. This is achieved at a speed of 135 km/h. If you assume a conservative climb rate of 2.5 m/s and fly for one hour with 60 liters of fuel, you theoretically gain 8,400 meters of altitude and have covered a distance of 135 km. Even with pessimistic rounding (8,000 meters) and a below-average glide ratio of 30, this results in a total range of 375 km. Therefore, 400 km is quite realistic. An important point is also that the jet becomes more efficient at high altitude.

What are the other advantages of the jet sustainer system?

The biggest advantage is the system's safety. In the extended state, the jet's drag is lower than that of an extended landing gear. The fast, fully automated start-up process of the turbine costs only about 30 to 35 meters of altitude. Operation is simple, via a display and a rotary knob. Furthermore, the jet is low-maintenance. The annual maintenance can be performed by the pilot themself. Except for the engine, no installed part has a TBO (Time Between Overhaul). However, in the 12 years the engine has been on the market, not a single one has had to be overhauled.

And what about the often-discussed topic of CO₂ neutrality?

The engine can be operated with HVO 100, a synthetic diesel that is CO₂-neutral. It is now available at many filling stations and leaves neither exhaust trails nor odors. We are working on including the use of e-fuels (synthetic fuels) in the certification.

Is the jet system still attractive for Standard Class competition pilots?

Experience with the system in numerous JS3s in competition use shows: The jet is the best sustainer system for competition pilots. The low weight impact of 13 kg is crucial. Competition pilots often fly with 20 to 25 liters of fuel, which is enough to get home and keeps the total system weight under 30 kg. That makes it the best specific system.

Which LS8 models can be retrofitted, and what steps are necessary?

We retrofit all LS8 models except for the LS8-b, as it already has an engine bay. The conversion takes place entirely at M&D Flugzeugbau. The fuel tanks are located in the outer water tanks of the wings to keep the weight in the fuselage low. Incidentally, a maintenance cover is also installed during this process, which facilitates the inspection and repair of the water system in this area. In addition, the engine, including the control unit, must of course be installed.

What does the retrofit cost, and how long does it take?

The retrofit of the LS8 to the jet system currently costs €31,730 net. The planned conversion time is two weeks. Eleven conversions have already been ordered, seven of which are scheduled to take place this winter. We expect certification in the first quarter of 2026.

Let's say one is flying in Australia. Is the jet offered as a kit?

Yes, we are planning a partnership with one aviation maintenance organization in Australia and one in the USA. In Europe, we at M&D will be the only maintenance organization offering the retrofit for the time being. But here too, we are in principle open to licensing another facility.

A dozen owners have already ordered. What is the best way to get convinced of the concept?

We are available to provide advice and support for inquiries from private individuals or clubs. Clubs, in particular, should not shy away. It's no secret that there are attractive ways for clubs to finance such projects, and M&D is also considering attractive financing models here. Interested?

We are happy to provide our factory LS4 Jet free of charge upon request. Just last week, the glider was visiting the Borken flying club. The members made a total of approx. 25 flights and put the jet through its paces. The feedback was uniformly positive, and they are now considering having the club's own LS aircraft retrofitted next year. Originally, the plan was to replace the gliders with a glider equipped with a regular sustainer. Now, Borken will have two club aircraft with jet systems in the future.

Is there an outlook on future developments or aircraft types?

We have continuously invested in the development of the jet system. In the meantime, we have developed a new controller and control unit and reduced the start-up time by almost 30%. The system now also features altitude-dependent engine control. For the future, retrofits are planned for the ASW 27 and thus also the ASG 29 glider versions. We also want to offer the turbine for the ASW 24 and ASW 28 models.

Keno, thank you very much for this comprehensive overview!

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