From the wind tunnel to the super-ellipse
Almost incompatible: very good climb, excellent glide even at high speeds, optimum thermalling performance and overall very good-natured flying characteristics. The Antares made it possible to fulfill these wishes.
The aerodynamic design is the result of a multi-year research project and was uncompromisingly designed as a unified whole. All conceivable opportunities for optimization were exploited. Nine different precisely harmonized wing profiles ensure minimal profile drag. On the underside of the profile, the laminar boundary layer is maintained up to 95 percent of the profile length.
Turbulator tape forces the transition to a turbulent boundary layer. According to studies commissioned by Lange Aviation, this form of boundary layer control does not exhibit any significant differences to boundary layer blowing if it is correctly adapted to the prevailing boundary layer. It is also less sensitive to dirt and damage.
On the upper side of the airfoil, the flow remains laminar up to 75 percent of the profile length. This represents the highest value currently achievable for airfoils without boundary layer suction. Furthermore, an additional negative flap position (-3°) can be selected for fast flight. As a consequence, very high airspeeds can be achieved with unprecedented gliding performance.
Only at airspeeds of 220 to 245 kph ( 119 to 132 kts ) (depending on the wing loading) do the airfoils exit the laminar flow drag bucket.
Wing planform
The wing planform of the Antares is characterized by an extremely slender superellipse. This geometry allows the induced drag to be reduced to the theoretical minimum. This corresponds to the optimum values of the untwisted elliptical wing without having to accept its critical stall characteristics.
The wide outer wings and winglets provide very good-natured characteristics. The winglets also allow the induced drag to be reduced by a further 5%. Thus, the induced drag of the 21.5 m (70.5 ft) wing is only 95% of the untwisted elliptical wing.
Perfection in detail
The Antares is equipped with a sufficiently large wing area to meet the requirements of a motor glider. In conjunction with the high aspect ratio, it guarantees excellent climbing ability with the lowest induced drag.
Wings and winglets are designed as a single unit. In perfect harmony with the wings, the winglets significantly reduce drag while also improving flight characteristics
The compact motor of the electric drive allows the realization of an optimal constriction of the fuselage and thus a further reduction of drag
Typical aerodynamic performance losses in the area of the fuselage-wing transition are minimized by a special design of the fuselage section and the use of special turbulent airfoils in the vicinity of the fuselage.
Handling
The Antares is extremely maneuverable due to the design of the wing control surfaces as continuous flaperons. The flaps are controlled by a novel control system. In addition, the consistent use of high-quality ball bearings instead of glide bearings has significantly reduced the frictional resistance in the entire control system, resulting in a very light-running control system.
Large tail surfaces with high aspect ratios and state-of-the-art airfoils ensure perfect controllability under all flight conditions and load states while keeping tail drag to a minimum.
High-extending, three-story cascading Schempp-Hirth-style airbrakes allow steep and safe landing approaches with minimal loss of lift. This has the effect that the stall speed is not significantly increased by the extension of the airbrakes.
All these factors make the Antares a very smooth to control, extremely agile airplane without appearing “nervous”. In flight, the Antares is stable and at the same time very responsive to thermal activity – offering maneuverability comparable to 15 m aircraft. For example, at 115 kph (62 kts) with the flaps in the neutral position, the Antares 21E only needs 3.4 s to complete a +/- 45° bank reversal (Antares23: 3.2 s; Antares20 3.2 s).
Antares 23 – Thoughts about the “Open”
Since its introduction in the 1950s, the oldest competition class in soaring has always been the one that stood for the greatest innovations – not regulated and therefore open to any design solution, no matter how elaborate (and expensive). And it is not without reason that the top technological achievements in glider design are called “super orchids”, which means that they are particularly rare and “exotic” in terms of technology.
For decades, the simple formula was that more wingspan automatically means better glide ratio and more overall performance. Therefore, around the turn of the millennium, aircraft with a wingspan of more than thirty meters and a best glide of 70 were created. Expectations were high. However, the targeted and achievable performance is disproportionate to the required input: The costs are immense and therefore only allow for the smallest production numbers.
In addition, more span naturally demands more strength. Despite all the innovations in materials and production, this also means more mass. After all, larger masses mean greater inertia, which already increases in square with the wingspan. A larger mass is not only unpleasantly noticeable in the air, but also with every necessary movement on the ground.
This inertia is particularly noticeable when thermalling, where another problem of large wingspans becomes unpleasantly apparent: the inner wing turns at low speed, while the outer wing turns faster – much faster if the wingspan is very large. Specifically, at 30 meters, the difference at 45 degrees bank angle can be 40 kph ( 21.6 kts ). To circle steeply and slowly at the same time in order to achieve the best climb in a confined space is something reserved for smaller aircraft.