DG Gliders >> DG-1000


	DG-1000

	In the beginning, there were only three 20 meter class two seaters on the market; all with very different characteristics: The ASK 21 was considered to be the ideal glider for flight training: robust, docile, and suitable for aerobatics. The Duo-Discus was the most modern two seater and was designed especially for cross-country flying. The DG-505 ORION was multitalented and combined good training capabilities, and very good performance in both cross-country and aerobatic flying. When we got together to discuss the long term plans for DG Flugzeugbau. During these discussions it became clear to us that we could design and construct a glider that combines all the positive characteristics of the three models mentioned above. The result was a plan for a two seater glider, the DG-1000. The Airfoil The selection of an appropriate wing section was a collaborative event which occupied many well known professors and their respective aerodynamic labs for many weeks. The final result is a laminar wing section designed by Horstmann/Quast from DLR Braunschweig. This section was reviewed and measured at Stuttgart University. The Technical University of Delft then completed the design with the addition of winglets and by optimizing the wing- fuselage intersection. In the end, two possible wing sections were left to choose from. One of them represented ultimate performance at best L/D speed , however it showed a strong drop in performance at higher speeds and likely possessed nasty stalling characteristics. The other option was slightly less efficient at best L/D, however much better above 160 km/h. This was combined with very docile stalling characteristics and low bug- and rain sensitivity. We believe that the small advantage of the glide ratio of the first profile is unattainable in normal flight, and that the docile stall characteristics and the low bug- and rain sensitivity of the second option were much more important. Naturally, we chose the second wing section. The Wing The DG-1000 can be flown with 2 wing-spans. For easier rigging each wing features a parting device at y=8600 m that is, at about the 17.2 meter point. For flying at the 18 meter span a set of 0.4 meter long wing tips with "miniwinglets" are added (similar to the standard DG-800 18m tips). This configuration is designed to produce good rolling qualities and predictable flight behavior. For cross-country flying the 20m wing tip extensions with integral winglets are added. Doubtless, the wing-planform will show some similarities to the Duo-Discus. It should be noted, however, that the selection of planform and dihedral was lead principally by aesthetics. Whether or not the wing has a single or double contour break, or if it is bent forwards or backwards makes little difference in performance. So of course we designed our glider to be sleek and pleasing to the eye. A perfect marriage of aesthetics and performance. We like to think of the DG-1000 as an aerodynamic work of art! In addition the four-part trapezoidal wing of the DG-1000 has a small advantage over a two-part trapezoidal plan form at low speeds. The carbon wings of the DG-505 are not heavy at all. But the weight of each DG-1000 wing is about 8 KG (!) less, (approx. 89 KG! ) The Fuselage The fuselage originates from the DG-505 and incorporates a variety of enhancements. The positive characteristics were carried over . The high seating position of the rear seat was not changed. This gives the rear pilot (usually the flight instructor) an excellent view. That is also why we have decided to keep the two-piece canopy. You can read our thoughts on why not to change to a single canopy on our website. Safety reasons were the main factor in our decision. Another important change was to the landing gear: We have designed a shock-absorbing, sophisticated new mechanism providing high comfort. The problem with two seaters is that the rear pilot sits exactly where the main wheel should be. As a result the glider is nose heavy on the ground. For this reason , most tandem two seaters have a nose wheel as well as a main wheel. This is a disadvantage for winch launching, as the tail wheel can often hit the ground when the winch cable tightens. This is not necessarily good for the structure, and is very unsettling for the flight student because the glider's attitude changes suddenly. Our wheel extends forward from the landing gear compartment beyond the centre of gravity. The DG-1000 therefore tends to sit up, even with a pilot in the front cockpit. The sudden pitch up on winch launch is avoided because the glider always rests on the tail wheel. The big spring gives an excellent comfort during taxiing and the wheel comes with a hydraulic disk brake. To remember: In those days the DuoDiscus came with a main wheel without any spring - like a Ka 7 or Ka 13! The Tailplane The sailplane has also been completely redesigned with new profile sections and optimized to the size of the wings. We want to install a small fin tank to compensate the C.G. shift due to water ballast in the wings. Furthermore we thought that it should be easy to adjust the C.G. depending on the cockpit loads in order to achieve the best handling and performance characteristics. There is a large difference between two heavy adults or one light juvenile flying, especially if they fly right after one another. Therefore we created a compartment in the vertical fin for ballast weights which is accessible via a removable panel. After removing the panel you can easily install one to nine brass weights into specified compartments to adjust the C.G. point as required.. Flight Performance: We believed we could predict that the DG-1000 would feature noticeable performance advantages in comparison to other gliders: The wing section is state-of-the-art. The wing-fuselage intersection was optimized for optimal boundary layer conditions with special airfoils in this area. Winglets are standard for the 20m span which performance-wise will result in a wingspan of approx. 21 meters. The drag of the nose wheel has been eliminated. Exact performance figures are available since flight comparison tests have been done. A flight with the Duo Discus proved these results! The theoretical calculations looked very promising: The min. rate of sink should be 0.51 m/sek at 28 kg/m2 wing loading (Solo flying). The best glide ratio was calculated at 1:46.5 with 42.8 kg/m2; (max. weight)! Motorization / Wing flaps /22 Meter span From the beginning we had planed to offer the DG-1000 with an engine later on - as a self-launcher or as a Turbo-version. We had just finished the development of the DG-505MB, which was the only motorized two seater glider in its class on the market. At the moment there is no need to design and type certify a motorized self-launching DG-1000, not to mention that the available production capacity for the "normal version" are at its limit. There are also plans to develop a version with wing flaps... but not in the near future. There will not be a version with larger wingspan (22 meters or more). To prepare for a span larger than 20m, the necessary reinforcements of the inner wing panels would result in higher mass for all versions and reduced rigging comfort. Because of "Murphy's Law" the maiden flight did not occur until July 28th, 2000.