Aerodynamics

 

A Glider-pilot’s Desire

Grundriss 20E
An aircraft which combines combining very good climbing characteristics, excellent glide ratios even at high speeds and optimum thermalling performance with overall very pleasant handling characteristics. This aerodynamic layout is the result of an ambitious research project. Being a completely new design, the aerodynamic outline of the Antares has been designed entirely as one piece. All possibilities for optimization have been considered.

 

Wing Geometry

An extremely slender super ellipse describes the outline of the Antares wing. This geometry makes it possible to reach the theoretical minimum of induced drag, which is the value of the untwisted elliptical wing. The unpleasant flight characteristics of the untwisted elliptical wing, however, have been avoided by the Antares design. The relatively wide outer wing combined with the winglet provides forgiving stall characteristics. The winglets also allow a further reduction of the induced drag by 5%. As a result, the induced drag of the 20 m Antares wing reaches only 95% of the value of a fully elliptical wing with the same wingspan.
 

Airfoils

Nine different airfoil sections, finely tuned to one another, provide minimum pressure drag and friction drag. The boundary layer remains laminar up to 95% of the wing chord on the lower surface of the wing, at which point turbulent flow is triggered using turbulator tape in order to avoid laminar separation bubbles. Research performed for Lange Aviation have shown that there is no discernable difference in performance between a well designed turbulator tape and triggering the boundary layer through blowing. On the on the upper surface, the boundary layer remains laminar up to 75% of the wing chord. This is the highest value currently available.

Wing GeometryFurthermore, an extra negative flap setting (-3°) is available. As a result, the Antares can be flown at high speed with previously unachieved gliding performance. The wing leaves the low drag bucket characteristic of laminar flow only after reaching airspeeds of 220 to 245 km/h (119 to 132 knots), depending on wing loading.

 

Detail Perfection / Fine Tuning

Wing GeometryThe Antares 20E possesses a wing area adapted to the needs of a motorglider.

This, together with a high aspect ratio of 32, guarantees excellent climbing characteristics in thermal flight.


  • Wing and winglets have been developed as a single unit. Being in perfect harmony with the wing, the winglets yield substantial drag reductions, while at the same time improving flight characteristics
  • The compact electric motor allows the realization of a fuselage shape with an aerodynamically optimal contraction ratio behind the cockpit, thus further reducing drag
  • Usual aerodynamic losses at the wing-fuselage junction are minimized by a careful design of the mid-fuselage section, and through the use of specifically designed turbulent airfoils close to the fuselage

Handling

tail aerodynamicsThe Antares 20E sports full span flaperons, which yield high maneuvrability. The movements of the flaperons are controlled using a novel control mechanism (patent pending). Furthermore, a consequent utilization of high performance low friction ball bearings instead of plain bearings substantially reduce friction in the control mechanisms, resulting in an aircraft which is extremely light on the controls.

Characteristic features of the stabilizers is that they are combine relative large surfaces with a high aspect ratio and modern airfoil sections. Stabilizer drag is kept at a minimum by ensuring that the stabilizers only need to produce very little lift when in steady flight.

The Antares comes equipped with large triple panel Schempp Hirth – type cascading airbrakes, allowing steep and safe landing approaches with little loss of lift. Extending the airbrakes has only a minimal effect on the stall speed.

All these factors combine to make the Antares 20E very light on the controls, yet agile without being nervous. The Antares 20E flies very stable, but is extremely sensitive to thermals, and has controllability comparative to that of a 15m sailplane. A +/- 45° curve change at 115 km/h (62 knots) requires only 3.2 s.

Antares 20E: the performance of the open class, and the handling of the 15 m class!