Electric Self-Launch Sailplane
FAI CLASS 13.5m
 
   
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Alisport Srl
Tel. (+39) 039.9212128
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Via Confalonieri, 22
Cremella (Lecco), Italy
   

 

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The Silent 2 Electro with its nose-mounted electric propulsion system constructed specifically for the Silent is the most modern and environmentally conscious design capable of satisfying the needs of ever increasing sailplane performance.

The electric motor installed in the nose of the glider with folding propeller blades is aerodynamically clean and has no additional drag during climbing or cruising flight.

The drag-reduction offered by the retractable landing gear, vertical-design winglets, and variable-position horizontal stabilizer, further expand the glide performance higher airspeeds.

Electric-powered flight does not necessarily require the steady climbing flight typical of self-launch gliders as the aerodynamically efficient nose-mounted propulsion system allows sustained level flight at cruise speeds with minimal energy consumption.

A pair of lithium polymer (LiPo) battery packs with a combined capacity of 4.3 kWh provides power. The two battery packs, each weighing 15.5 kg (34.2 lbs), are positioned as close to the center of gravity as possible. They are readily accessible and removable via an access panel on the upper surface of the fuselage.

The batteries are transportable allowing them to be charged at any location, not just on board the sailplane.
Unlike NiCd or lead-acid batteries, LiPo batteries experience negligible loss of charge (typically 1% per month) when stored at ambient temperatures.

The usual batteries needed to power glider avionics can be eliminated as the LiPo propulsion batteries have enough extra capacity for all other on-board power requirements. The lifespan of the batteries is estimated to be approximately 1,500 cycles to full discharge, after which the batteries are still capable of holding 70% to 80% of a full charge.

Recharging is performed with a 1,200 W external charger which includes a Battery Management System (BMS) designed specifically to balance the charging of LiPo batteries. During charging the BMS controls the voltage to the various cells that make up the battery packs so that their voltages are all within 0.02 volts.

TECHNICAL HIGHLIGHTS

  • Motor with smaller size, lighter weight, higher power output, and greater reliability when compared with any internal combustion engine
  • Significant reduction in noise; the use of a radio headset is unnecessary during powered flight.
  • Extremely clean due to elimination of fuel, oil, exhaust fumes, etc.   
  • Elimination of flammable fuel on board
  • Secure and instant start-up; the motor requires no warm-up prior to application of full power
  • Almost complete absence of vibration; the only moving parts are the propeller and the rotor
  • Motor maintenance is essentially unnecessary
  • The nose-mounted motor is on the fuselage center-line and thus has no forward pitching moment to create take-off difficulties as is typical of pylon mounted propellers
  • No loss of motor power as a function of altitude; performance is unvaried with respect to atmospheric conditions
  • Motor use is extremely simple; no raising of a pylon, simply turn on the master and apply power
  • Complete absence of aerodynamic resistance (engine pylon, etc.) and consequently better flight performance
  • Mechanical simplicity and uncomplicated use of the entire system, when compared to solutions with a retractable powerplant
  • No change to the aerodynamics when using the motor
  • No change to the center of gravity when changing between powered and unpowered flight.
  • Propeller located in front of the cockpit and safely visible to the pilot at all times
  • Complete availability of extra electric energy for even the most well-equipped instrument panel

The class-leading Silent 2 Electro is a high-performance light self-launching sailplane for recreational and sport flying.

The wings have an elliptical planform, vertical design winglets, and a span of 13.2 meters. The wing structure includes extensive use of carbon fiber, both in the sandwich skins and in the tapered
I-beam wing spar which uses pultruded carbon rods for the spar caps. The wing geometry is unique in that it varies non-linearly from the root to the tip, both in overall planform shape and in wing section profile. The flaperons stretch for 11.0 meters of the full wingspan and their range of motion varies from positive landing L, to +1 for thermalling, to 0, -1, and S reflex positions for cruising.

The sailplane is trimmed in pitch via an innovative variable-position horizontal stabilizer. The stabilizer position is governed by the flaperon setting: the five settings of the flap control produce corresponding changes to the stabilizer incidence, thus defining the trim airspeed in relation to the flap requirements. The conventional elevator remains in trail, minimizing trim drag.



The ingenious trim system, the elliptical planform geometry of the tailplane, the vertical design winglets, and the retractable landing gear all combine to yield improved performance over a wide range of airspeeds.

Performance
Stall speed (VS): < 65 km/h (40 mph)
Maneuvering speed (VA): 150 km/h (93 mph)
Maximum speed (VNE):

220 km/h (137 mph)

Maximum L/D: 40 at 90 km/h (56 mph)
Minimum sink rate: 0.60 m/s (118 ft/min) at 85 km/h (53 mph)
Takeoff distance (asphalt):   ~140 m (~460 ft)
Takeoff distance (grass):   ~160 m (~525 ft)
Landing distance:  ~100 m (330 ft)
Powered climb rate:  ~2.0 m/s (~400 ft/min)

Glider Technical Data
Wing span: 13.2 m (43,3 ft)
Length: 6.35 m (20.8 ft)
Height: 1.25 m (4.1 ft)
Aspect ratio: 20
Wing area: 8.9 m2 (95.8 ft2)
Planform: Elliptical (with winglets)
Profile: IMD 050 (16%)
Empty weight: 205 kg (452 lbs)
Maximum payload: 105 kg (231.5 lbs)
Structural max. takeoff / landing  weight: 315 kg (694.5 (lbs)
Wing load factors:

+5.3 g / -2.65 g
(at 150 km/h at 315 kg)
+4.0 g / -1.5
(at 220 km/h at 315 kg)

Wing loading at 300 kg (661 lbs): 34 kg/m2 (7 lb/ft2)
Flap settings:

L  +1  0  -1  S

Conventional air brakes

Fully automatic control connections

Retractable landing gear


Brushless DC Electric Motor Technical Data
Motor power: 22.0 kW
Motor weight: 6.5 kg (14.3 lbs)
Motor speed: 4,500 rpm
Propeller speed: 4,500 rpm
Propeller diameter: 1.00 m (39.4 in)
Weight of batteries: 31.0 kg (68.3 lbs)
Battery capacity: 4.3 kWh
Standard charging time: approx. 150 min at 220V 


STANDARD CONFIGURATION:

Carbon and glass fiber COMPOSITE FUSELAGE with epoxy resin.
Composite SANDWICH WING SKINS, pultruded carbon spars.
HORIZONTAL TAILPLANE of elliptical planform.
Variable incidence stabilizer and conventional elevator.
T-TAIL and large rudder surface.
Generous 11M FLAPERONS; the flap range is L + 1 0 - 1 S.
Fully AUTOMATIC CONTROL CONNECTIONS for wings, fuselage and horizontal tailplane.
Removable VERTICAL-DESIGN WINGLETS.
One piece HINGED TIP-UP CANOPY, side window with air vent.
Main wheel BRAKE activated via air-brake control aft travel. AUTOMATIC TRIM connected to the flap lever to get the ideal trimming.
Polymer WING-TIP WHEELS with fairing, for taxiing on asphalt or grass.
RETRACTABLE main wheel, 4.00x4” 6-ply tire with tube.
Fixed TAIL WHEEL (Steerable with fairing as option).
In-flight ADJUSTABLE RUDDER pedals.
Central INSTRUMENT POD and engine control.
BASIC FLIGHT INSTRUMENTS: 80mm altimeter, 57mm air-speed indicator, compass, Winter 57mm variometer, total energy probe (Althaus).
4-POINT HARNESS with quick-release.
Cockpit side POCKET, HEAD REST, SEAT-PAN LINER WITH CUSHION, TOOL POUCH.
ELECTRIC MOTOR, installed in the nose of the glider
Composite FOLDING PROPELLER blades

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