Antares 21E

The new one from Lange Aviation

Can a well-tuned aircraft like the Antares 20E be improved further upon? Lange Aviation makes every effort and is now introducing the Antares 21E.

Why develop something new, when the owners of Antares 20E are consistently very satisfied with their high-tech acquisition? The 20 m aircraft appeared 15 years ago with cutting edge airfoils, a trailblazing electric propulsion that even today remains relevant with an un-beaten efficiency for self-launching, as well as numerous intelligent detail solutions for pilot comfort. Using a super-elliptic geometry with optimized lift distribution, the wing was designed to carry the heavier load of a self-launching sailplane.  

When the Antares pilots were inquired about suggestions for improvements, there was one area which came to mind: A common wish was to be able to climb well also in very weak thermals. Due to higher masses, self-launching sailplanes, even ones with electric propulsion, will at some point reach their limits under such conditions. 

But limits exist to be pushed. The new Antares 21E with a wingspan of 21.5 m (70.5 ft) does so by reducing the minimum sink rate, by improving the glide performance in the lower to intermediate speed range, and, finally, by improving the maximum glide ratio.

At higher speeds, an increased wing-loading also helps improve matters.

Improved climb performance does not always come at the cost of a larger wing area and the accompanying lower wing loading. The determining factor is the aspect ratio of the wing. At low speeds, the induced drag makes up most of the total drag of the aircraft, and it is directly dependent on the aspect ratio.

Therefore, with the Antares 20E as a starting point, the Antares 21E receives a slender new outer wing with a swept back leading edge, new airfoils and 1.5 m (4.9 ft) more wingspan. This drives the aspect ratio up to 35.8. Compared to the Antares 20E, which has an aspect ratio of 32, this reduces the minimum sink rate by 10% - thus improving the thermalling characteristics of the aircraft.  

The aerodynamic optimization of the winglets, which are now equipped with turbulator tape on the upper surface, yields another small additional contribution. This allows the winglets to effectively support low speed flight with unfavorable flow conditions.

In order to ensure that the good thermalling performance can be controlled comfortably and with low rudder forces, the vertical stabilizer, which has been retained from the Antares 20E, has been equipped with a deeper rudder with new airfoils.  The new rudder improves the rudder effect, thus making the 21.5 m aircraft more agile, while the required rudder forces only increase minimally. The longer outer wings and the corresponding structural strengthening of the inner wing lead to an increased structural weight of only 5 kg (11 lb), so that the minimum wing loading is not impaired.

The two inner sections of the four-part wing are equipped with three integral water ballast compartments, capable of carrying 126 l (33.3 US Gal.) of water ballast.

A two-level tank in the vertical stabilizer serves to offset translations of the center of gravity due to the ballast in the outer part of the inner wing. This makes an open-class style highest wing-loading of 55 kg/m2 (11.26 lb/ft2) possible. The computer-controlled water ballast management is on-par with the rest of the high-tech aircraft. The eight electro-magnetic dump-valves are individually controlled and monitored. With the opening of the outer wing tanks, the tail tank is opened correspondingly, draining only the amount needed to maintain an optimal center of gravity position.

The landing gear is more than capable of handling the increased MTOW of 710 kg (1565 lb).  Using the same landing gear as the Antares 23E, it is rated for an aircraft mass of 850 kg (1874 lb). In the case of a crash, the landing gear can absorb a highest possible amount of energy. The safety cockpit has been adopted from the Antares 20E. Here again, opportunities for improvement have been used. Notably the internal airflow through the cockpit has been re-worked, with the dual aim of improving the cockpit cooling and of minimizing air extraction drag. In the Antares 21E, the cockpit air is led through multiple outlets and passages, and it is ejected at the rear end of the fuselage. While the various outlet cross sections are sized to minimize impulse losses, the elaborate canopy sealing avoids drag-inducing leakage flows.    

The advantage of this ingenious air-condition-system, which provides an effective and well controllable fresh air supply and cooling, is that it substantially reduces the cockpit noise level – another indication that this novel type of cockpit ventilation avoids aerodynamic losses where possible. 

A final aspect of the cockpit ventilation is that changes in airspeed can immediately be felt on one’s skin, making flying even more intuitive.

The Antares 21E propulsive system has also undergone improvements. The electric motor, which has been proven in the Antares 20E, the Antares 23E and the Arcus E, is now in its second generation. By re-working the windings of the motor, the efficiency could be increased even further to 93.7%, which also improves the motor cooling.  One full charge yields more than 3500 m (11500 ft) of climb altitude.

The propulsive system is controlled and monitored by a new generation of main computer (EDCS-4). A larger and easier to read display, combined with an improved audio output, makes all important and relevant data available to the pilot. The computer now works with software revision 7, a release that was aimed at further simplifying maintenance and servicing. A direct physical inspection for the ARC must now only be performed every 3 years. In order to protect the onboard charger, the Antares 21E, just like modern electric cars, comes equipped with an EVSE (electric vehicle supply equipment) that permanently monitors the grid outlet and protects against damages due to transient voltage irregularities.

Technical data

Geometry 21E
Wing Span 21.5 m / 70.5 ft
Wing Area 12.9 m² / 139 ft²
Aspect Ratio 31,7
Fuselage Length 7.40 m / 24.3 ft
Fuselage Height 1.64 m / 5.4 ft
Weight 21E
Empty Weight 480 kg / 1047 lb
Maximum Weight 710 kg / 1565 lb
Waterballast 126 l / 33.3 USgal
Min. Wing Loading * 42,6 kg/m² / 8.7 lb/ft²
Max. Wing Loading 55.0 kg/m² / 11.3 lb/ft²
Glide Performance 21E
Best Glide Ratio 57,5
Min. Sink Rate (at weight 550 kg / 1212 lb)* 0,45 m/s / 89 ft/min
Stall Speed (at weight 550 kg / 1212 lb)* 73 km/h /39 kts
Motor data 21E
Motor DC/DC brushless
Power 42 kW / 57 hp
Revolutions 1500 rpm
Maximum Revolutions 1700 rpm
Climbing Performance 21E
Max. Climb Rate* 4.4 m/s / 866 ft/min
Max. Climb Altitude* 3500 m / 11483 ft

* Pilot+Parachute = 70kg / 154 lb

3-view Antares 21E