FES Retrofit possible for nearly all LS6 and LS8 gliders

The FEStrofit conversion uses batteries in the wings instead of the fuselage, as was done previously. Why?

Generally, there are two possibilities for accommodating the batteries in these types of aircraft: either in the fuselage or in the wings. The majority of people interested in a conversion have now opted for the wing batteries. Due to the higher weight of non-load-bearing parts, the fuselage batteries would have the disadvantage of restricting the payload. Thus, despite the higher cost, the interest in the wing batteries was significantly greater.

What else distinguishes the wing batteries?

Especially the higher capacity. This is currently specified as up to 9 kWh. Even if this specification might need to be slightly corrected downwards due to structural limitations, the capacity would be significantly higher than the fuselage batteries, which in the current Generation 2 have a capacity of 4.2 kWh.

What is the performance like with the new batteries?

The FES is primarily intended to be used for extending the range in economical cruise flight. Here, we hope for an increase to 150 – 160 km. In most cases, that should be enough for a safe return home plus a reserve.

What advantages does the FES system offer compared to conventional home-return aids?

The FES system has the huge advantage that it is fully operational within two seconds. And should it ever fail, the drag remains low, and you don't have to contend with significantly increased sink rates as with conventional, deployable systems. Furthermore, the operation is extremely simple. We have sold many LS8e or DG1001e to clubs, and even pilots with little experience have had virtually no operational problems.

What is the new minimum wing loading, and will the LS8 still be attractive for competitions with the conversion?

The lowest wing loading will probably be about 40 kg/m2. However, the use of our own LS8e neo in numerous competitions shows that this weight is okay in most cases. The additional drag from the propellers also appears to have very little to no effect.

Will the batteries still be removable?

In all likelihood, yes. However, I can't say yet how complicated that will be.

Which LS6/LS8 series would be eligible for a conversion, and approximately how many aircraft is this?

The LS8-a and LS8-18 series, as well as all LS6 series from the LS6-b onwards, can be converted. In total, this amounts to about 600 aircraft that would be suitable for a conversion.

What steps does the conversion involve, and what are the challenges?

It's a huge effort to provide all the calculations beforehand that are necessary as evidence for the structure during a conversion. That will take a while, and we will only start this process once five options have been signed.

For the installation of the batteries in the wing, the area where the inner water tanks are currently located is used. In the fuselage, the installation of the motor and all the electronics is naturally necessary. Additionally, work such as relocating the nose hook or the holder for the trim lead is required. Finally, extensive flight testing with all evidence for certification is necessary.

What are the costs for a conversion?

We have currently calculated €80,000 net for the entire conversion. That sounds enormous, but the components already swallow up a large part of this sum. The certification processes are also becoming significantly more complex. Therefore, we are trying to increasingly fall back on existing, already certified components and parts. For example, there is an initiative for the batteries so that, in the future, all manufacturers will ideally use the same battery type.

Will there one day be a self-launching LS8 with the FES system?

Since we ourselves have had an LS8 with FES, the "71," for many years now, there is actually a small personal interest in this regard. We have already checked this internally once, but unfortunately, we have concluded that it will not be feasible with the LS8. The complete redesign of the landing gear and other components to increase the propeller's ground clearance would simply be too complex.

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