Miles Gore-Brown from Australia

 

As a B777 Captain with Singapore Airlines I am very fortunate to have the opportunity to visit glider factories on some of my trips. I have been very interested in the progress of the new LS10 so during one of my recent Frankfurt trips I took the opportunity to visit the DG factory and have a look at the LS 10. The following is a detailed description of the new glider along with a brief history of its development.

 

There has been a flurry of new 18 meter gliders appearing over the past two years, with the most recent JSF1 from South Africa, ASG29, and Antares entering the stable. This is an indication of where the manufactures feel the future demand will be for new gliders. It is a common view that 15 meter class will probably not move forward from the current fleet of gliders, the new Diana being the only exception. Open class is extremely expensive and outside the budget of many let alone the small army of people you need to get you into the air. Standard class will always be a popular class as these gliders are affordable and very easy to handle. Leaving 18 meter class which is relatively new and subsequently has performance boundaries yet to be established, allowing room for future development. As such many of the manufacturers are placing a lot of effort in developing the new generation 18 meter gliders. Schempp-Hirth was the first manufacturer to develop and produce the first really competitive 18 meter glider, the Ventus2cx/t. Other manufacturers followed, with DG, LAK and ASG producing the current fold of new 18 meter gliders. It maybe be pertinent to mention that all the manufacturers have made available their standard class gliders with 18 meter tips, the latest being the Discus 2.

Prior to the bankruptcy of the LS factory, LS were in the process of developing their own new entry into the 18 meter class. Moving forward from their experience with the extremely popular LS8/-18 and less known LS9 they started to develop the LS10. Unfortunately the LS factory never managed to finish development of the LS10 except to build the very green original prototype. The factory went into bankruptcy before further development of the LS10 could take place.

The original concept was to produce two models of the LS10, one purely for the competition pilot, which is the one in current production and another model for the more recreational pilot. The main difference between the two models was the fuselage. The ?recreational? LS10 had a wider taller fuselage to provide a little more room, all other aspects of the glider were the same. The bigger fuselage will not be placed in production.

In 2003 DG announced that is was to take over LS, taking possession of all moulds, spares, jigs etc. In September 2004 DG commenced production of the first LS8 and LS8-18 gliders with EASA certification of the first DG produced LS8 taking place in August 2005.

The production of these gliders is now well established at the DG plant with the LS8 turbo version being offered. The LS10 prototype gathered dust while the DG factory re-established the LS brand.

DG maintains a strict policy to produce the LS gliders as they were originally produced by LS but to add many well established DG ideas into their gliders, such as their patented DEI-NT (Digital Electronic Indicator- New Technology) turbo engine control system, accessories and superb finish quality. DG have always been a leader in producing gliders that are extremely well finished without the common gelcoat cracking problems seen from the majority of the other glider manufacturer?s. DG further expanded the performance of the LS8 by increasing the maximum allowable wing loading of the 18 meter version with the incorporation of the larger 5 inch wheel.

After the DG factory managed to catch their breath once the LS8 was well established in their production process the design team started to assess the viability of the LS10. Holger Back (previous world Champion) became the LS 10 production manager and has been working very hard to see the production of the LS10 come to fruition.

DG was adamant that they wanted to produce the LS10 along the lines of the original LS design, emphasizing the superb handling of the LS gliders and optimizing the performance. After DG board approval the LS10 prototype was dusted off to start further development and assessment of the design.

The LS10 design remained essentially the same as the original LS aircraft with extensive work being carried out to reduce the drag around the wing to fuselage area. DG also incorporated a lot of the DG production methods into the LS10 to help standardize the way the factory produce gliders. Other small changes such as the wing tip connections have done away with the knurled screw and replaced it with a self locating pip pin arrangements. This makes wing tip attachment essentially a push and click rather than rubbing the skin off your finger with the old screw arrangement.

The main aspect of the LS10 design that the DG factory spent a lot of time with was the determination of the position for the wing break for the 18 meter wing tip attachment. Issues such as panel weight, trailer length requirements and most important the optimized position for weight and structural considerations needed to be addressed. It was finally decided to make the break at 7 meters from the wing root which is only 0.1 meter shorter than where the break for the LS8-18 occurs. This makes the LS10 quite unique as the majority of current 18 meter gliders have shorter inner panels and consequently longer and heavier outer panels.

The decision to break the LS10 wing at 7 meters has several advantages but most importantly it is optimized for structural and weight considerations. Inner panel weight is approximately 64kg which is comparable to the weight of the LS8 main wing panel, but a little heavier than the shorter inner panels found on the ASG 29. The 2 meter outer panel is very light and easily handled by one person.

The appearance of the LS10 could be mistaken for the LS8-18 to the untrained eye. After having spent a few hours at the factory crawling all over the glider I noticed some subtle changes. Common fuselage, wing and tail plane components from the LS8 are used throughout the LS10.

The fuselage is essentially exactly the same externally as the LS 8 except being .023 meter longer. The general shape and sleek lines have been maintained. This provides for a very light weight fuselage resulting in the LS10 turbo empty weight of approximately 320 kg, which is considerable less than the empty weight of the Ventus2cxt. However what does stand out is the higher stance of the glider with the new 5 inch wheel. The larger wheel has also been carried over to the current LS8 production which makes for safer paddock landings, easier ground handling and increased maximum all up weight of the LS8 in 18 meter configuration.

In the cockpit DG have included several features found on current DG gliders. The seat pan has been modified at the knee area so that two batteries can be located in the forward portion of the cockpit, necessary for the lighter pilot. This area is also where the DEI module is fitted. The wheel brake has been removed from the rudder pedal system and now is incorporated in the dive brake mechanism together with a "Piggott-Hook". Premium cloth interior with integral pockets and general fit out in the cockpit is an improvement on that found in the original LS gliders.

The NOAH system can be factory fitted in the cockpit without taking up huge amounts of space or reducing the head room, with a subsequent weight penalty of only 3.5 kg.

Flap and dive brake controls are found on the left side of the cockpit wall with the standard LS undercarriage lever on the right hand side of the cockpit sill. Cable release is easy at hand on the forward left hand cockpit sill. The canopy and integrated instrument panel are very similar to that found in previous LS models except that the instrument panel is not continued deep into the seat pan. This helps provide the space for the under seat battery installation. The head rest and seat adjustments are all retained to cater for average pilot shapes and sizes. Nose mounted ballast is available to cater for the lighter pilot.

One distinctive feature that is incorporated in the LS10 fuselage is the bug wiper garage. Even though the wing of the LS10 has been designed to be bug tolerant, fitment of bug wipers does not result in a drag penalty as they fit perfectly into the fuselage garage. The distinctive aluminum-carbon design of the bug wiper goes one step further to make the LS10 a distinctive high tech glider.

 

In addition to the integral bug wiper garages, solar panels are also integrated into the fuselage turtle deck to provide continual battery charging. Two normal batteries are sufficient to provide the required electrical demand for flight inclusive of (optional) bug wiper and turbo operation.

The wing of the LS10 is completely new and bears very little resemblance to the LS8-18 wing. Wing profile has been specifically designed to provide optimal performance at the high speed range while providing low rain and bug sensitivity.

It was apparent that the wing root chord was narrower than that of the LS8 with a very gentle taper to a wider chord at the tip resulting in an aspect ratio of 28.3. The 18 meter winglet is wide and well blended complementing the general wing shape and plan form. With a total wing area of 11.45 sq meters the LS10 wing area is almost the same as that found on the LS8-18. In the turbo version this allows for a wing loading range from 34.9kg/m2 up to 52.4kg/m2, at a maximum all up weight of 600kg.

The LS10 wing has been described as being a ?soft? wing which provides for a smooth ride and excellent feel of the air. This has been possible by the fact that the wing break has been chosen as far out to the tip as possible. As the wing break is further out towards the tip the spar is consequently less stiff and subsequently lighter than those wings with the wing break closer to the fuselage. The original LS10 prototype has the wing break at around 6 meters. The prototype wing is heavier and stiffer than the current production wing.

Roll control is achieved by full span flaperons, incorporating an end plate mounted at the wing root end of the flaperons. The end plate has been installed to cut down on the drag losses caused by air flowing around the deflected flaperons. 

All wing flight control surfaces are internally sealed and incorporate a low friction flight control system. This provides the LS ?feel? and helps reduce the control loads and friction. At the time of writing the two prototype LS10 gliders are being used to determine the trades and losses by having the flight control surfaces both internally and externally sealed. It was mentioned by the factory that it is more than likely that the surfaces will have external mylar seals fitted in addition to internal sealing. The final decision on the sealing will more than likely be made by the end of the current European soaring season.

The LS10 is also offered with 15 meter tips. After further development and redesign the 15meter tips will be quite different from the original wide chord deep curved LS8 tip. The 15 meter tips are more in line with the current tips offered on other DG models.

With the wing break at 7 meters means the (15meter) tips are only 0.5 meters long. This makes the tips easy to handle, easy to fit into a trailer and because of their small size considerably cheaper than the 15 meter tip options offered for the Ventus2 and ASG29.

The price of the LS10 15 meter tips is expected be approximately AUD 4.500. So for a little extra you get two competitive gliders, the LS10 with the extra 15 meter tips and the pure 18 meter version. With the current multi class handicap system you could fly the LS10 in either 15 meter or 18 meter class and be confident that your are flying a glider at the top of the ladder in both classes.

The LS10 features a unique new water ballast system, which has been specially designed for competition and record flying. The new water ballast system consists of two independent water tanks in each wing and two separate water tanks in the fin.

Internally the wing has the capacity to hold 190 litres (95 litres per wing) in two completely independent water ballast tanks. Each wing incorporates three manual dump valves, two for the inner panel and one for the outer panel. The dump valves and the associated mechanism are essentially the same as that found in the LS8. The wing water ballast system is combined with two completely separate water tanks in the fin to provide for optimum c of g control throughout the water ballast weight range. Total tail tank capacity is 7.5 litres. One tail tank dump control is connected to the outer wing panel water dump control with inner wing tank connected to the remaining tail tank. Normal operation requires the outer panels to be dumped last. In addition the fin also has provisions for a battery box for the heavier pilot.

Currently the factory is looking at the option of providing a fuselage water tank for those gliders without the turbo fitted. This will be necessary to allow the glider to reach the maximum all up weight of 600kg with an average pilot weight.

The LS10 is offered with or without the turbo fitted. However the LS10 is made turbo ready which means that the engine compartment is incorporated in all production gliders.

The LS10 turbo (st) is fitted with the 23hp Solo-2350 turbo. This is an extra 5hp (approx 30%) than the turbo offered in the ASG29. Current LS10-st performance information at ISA MSL indicates a climb rate of 1.3m/s is achievable at 420kg.

The turbo engine is controlled by the DG patented Digital Engine Indicator (DEI) fully automated engine control system. The DEI is an automatic, solid state, total engine control with alerts and diagnostic functions. Engine operation is automatic once the ignition switch is selected. From that point on the engine is automatically monitored right up to the start. All the pilot needs to do, is turn the ignition switch on, which then extends, primes, and provides ignition. The pilot essentially does not need to do anything other than fly the glider at the appropriate speed, pull the decompression lever located on the left hand side of the cockpit and wait for the engine to start. The DEI monitors ignition, temperatures, fuel, running times etc. Shut down and retraction of the engine/turbo is also fully automatic, inclusive of stowing the prop in the correct position. This system has been shown to be an easy and safe system, requiring minimal pilot input at the time when the pilot needs to be concentrating on the possibility of a field landing. A full description of the DEI system can be found here.

The DEI system also has provisions for undercarriage and stall warning audio signals. These can be selected within the system with the undercarriage warning requiring minor electrical wiring installation.

The LS10-st version has two fuel tank options. Standard 13 litre tank provides approximately 90 minutes of engine time or approximately 300km saw tooth range. An optional 17 litre tank is available. Fuel tank location is above the wing spar in the turtle deck behind the pilots head. With the standard 13 litre tank there is adequate spare space for light luggage/equipment. If the optional 17 litre tank is installed limited space is available for equipment. The fuel tank is filled by an electric pump controlled through the DEI system.

At the time of writing the performance of the LS10 has not been measured by flight test. Factory published computed performance data indicates a best L/D of 50 in 18meter version and 45 in 15 meter version. Pilot assessment at recent competitions indicates the actual performance in 18 meter configuration is better than the computer data. Final flight performance testing is yet to be completed.

The prototype LS10 has achieved encouraging results in competitions since 2005. The LS10 was placed first in the 2005 German Nationals, second in the 2005 European Nationals and most recently placed first in the 2007 Pre-Worlds in Germany. These results are very encouraging especially considering that these results were achieved by the two prototypes and flown in competitions where the majority of entrants were made up of Ventus2 and ASG29 gliders.

Comparison of the LS10 against the current top performing 18 meter gliders such as the ASG29 and Ventus2cx indicates that the LS10 at an early stage in its development is very competitive. Specifications of these three gliders are somewhat different with the ASG29 having the largest aspect ratio of 31 and smallest wing area of 10.5 sqm. The LS10 has a smaller aspect ratio (28.3) but the largest wing area of all current 18 meter gliders at 11.45 sqm and consequently a marginally lower maximum wing loading.

In conclusion the LS10 has been worth waiting for. The encouraging results from recent competitions and the continual evolution of the LS10 will put the LS10 at the top of the competition ladder. The attention to detail and first class finish will place the LS10 at the forefront of the 18 meter range of gliders.

For more information on the LS10 contact the New Zealand agent Paul Buchanan or visit the DG website.