THE NEW RACING STANDARD CLASS GLIDER
The ASW-28 is Schleicher's new high performance glider for the FAI-Standard Class. This glider incorporates the very latest technology, both in wing section and boundary layer control, and uses the most advanced carbon, aramid and plyethylene fibers in construction. The ASW-28 will be type certified for cloud flying and semi-aerobatics.
Current modern design theory leads us to examine the climb portion of the performance as much as the run part. This leads to a sailplane which will climb a little better and run a little better than current design. The ASW-28 will be lighter, more crashworthy and safer. Taken all together, this is a large step forward for Alexander Schleicher.
A more detailed view of the ASW-28 shows the roomy safety cockpit offers all modern comforts and ease of operation, even for tall pilots. The cockpit, designed according to latest research results in the field of safety and accident protection, includes an optional glider rescue system. The shock-mounted retractable landing gear with crush zones in the steel struts for overload and hydraulic disc brake, the adjustable back rest, the upwards hinging instrument panel and the speed trim, are only some of the many available conveniences.
The high performance wing airfoil with boundary layer control by menas of turbulator holes or suitable trip devices like ZZ tape, combined with an outstanding construction quality, imparts to the ASW-28 flight performances that are superior to those of the former racing class gliders. Due to the high construction quality of the wing and the control surface gap sealing a production wing with 85% laminar airflow along the underside has become possible. The sophisticated control linkage system gives high maneuverability and docile flight characteristics, even in landing approach.
The low drag airfoil of the "T" tail (elevator with stabiliser) was developed by the Delft University of Technology. Elevator and rudder are new technology sandwiches of aramid fiber/plastics with a hard foam core. All control surface hinges of the wing and tail unit use needle bearings or precise uniball joints. While desirable feedback from air loads at the control surfaces can still just be felt at the stick, the hand forces for the pilot are comfortable - a precondition for non-fatigue flying.
- Sprung landing gear with large 5" wheel and 10 cm normal stroke, for overload using crush zone of struts
- Hydraulic disc brake
- Tail wheel with faring
- Instrument panel hinging upwards with the canopy
- Nose and C.G. tow release coupling
- In flight adjustable back rest with integrated head rest
- Safety harness with quick-release center lock
- Battery storage space in the baggage compartment (designed to withstand 25G's!) and in the fin
- 3-way nozzle (multi-probe) in the fin.
- Directional air vent front canopy de-mist
Glider, higher mid wing configuration with T-tail. Automatic connections for all controls (aileron, airbrakes, and elevator) and water ballast actuation.
Monocoque fuselage of fiber-composite structure (CRP, Aramid, Polyethylene and GRP) with roomy safety cockpit.
In flight adjustable rudder pedals.
TOST C.G. combi tow release coupling, covered in flight by the landing gear doors, and TOST aero tow release coupling in the fuselage nose.
Rubber-shock-mounted, retractable landing gear, using a large 5.00-5 wheel, installed in a box which is sealed and airtight from the fuselage interior. Drag strut with designed weak link in case of overload.
Hydraulic disc brake which is connected to the airbrake lever.
Pneumatic tailwheel 210 x 65.
Optimum cockpit ventilation through intake in the fuselage nose with continuously adjustable outlets, one on the front canopy frame and the other through a directionally adjustable airnozzle on the right side of the cockpit wall. Cockpit ventilation is so good most pilots almost never open the side window.
The full-vision, gas-spring assisted canopy (with left side sliding window) is hinged at the front. Tongue and groove type sealing for the canopy frame and a specially shaped rear frame section for the purpose of a safe emergency jettison.
Water ballast in the wing leading edge is filled into so called "wet surface tanks," separated in two compartments per wing for the purpose of facilitating take offs with partial water ballast. The mechanical valve actuators are connected automatically when rigging the sailplane. Due to the design of the spar and leading edge web we achieved a small but favorable C.G. shift with water load. For fine tuning the C.G., a fin water tank is available as an option as well as for compensating for different cockpit loads. To avoid water damage to the structure, extra inner tank linings are installed as well as ventilation throught the winglet area. Filling is done through two faired outlets on the wing topside, outboard near the aileron break. Ballast capacity is approximately 110 kg.
The instrument panel is made to hinge upwards with the canopy; even when the canopy is open, the instruments remain covered. When the canopy emergency jettison system is operated, the canopy together with the instrument panel covering can be removed and the instruments are easily accessible.
BOARD EQUIPMENT AND ACCESSORIES
Static pressure vents (for the A.S.I.) in the fuselage tail boom left and right. Pitot, Static pressure and TE-compensation through 3-way-nozzle (multi-probe)in the fin. VHF antenna in the fin.
Cantilever, two-part quadruple-tapered wing planform with latest laminar airfoil; when flown high speed the laminar airflow at the wing underside goes back to the aileron gaps. upon specific directions by Schleicher, the airfoil was developed for the ASW-28 design by the faculty of Aerospace Engineering of the TU Delft. Tolerance to small scale micro-turbulence was regarded. Planform and airfoil of the outer wing have been modified for detachable winglets using the latest airfoil design. The wing surface is a sandwich of carbon fiber/plastics with a hard foam core; wing spars with double flanges. Double panel airbrakes of metal and CFRP are on the wing upper surface in sealed compartments with spring cover plates. Push rods are sealed by bellows. The wing assembly is straightforward with a conventional tongue and fork spar extension secured with cylindrical main pins. Each wing panel is extremely light weight. Control surface gaps on the wing upper and under side are sealed by plastic tape. Turbulators are on the under side and in front of the ailerons.
T-tail (elevator with stabilizer) with low-drag airfoil, developed especially for the ASW 28 project by the TU Delft. Control surface gaps on both sides are sealed with plastic tape and turbulators are on both sides in front of the control surface hinge line.
The stabilizer is built in CRP-sandwich-construction. The vertical fin is built in GRP-Aramid-construction because of VHF-antenna radiation. The elevator and rudder are new-technology sandwiches of Aramid fiber / plastics with a hard foam core. The ailerons and flaps are of CRP monocoque construction which gives extremely light and stiff control surfaces.
CONTROL CIRCUITS AND FITTINGS
Aileron, elevator, flaps, and airbrakes are actuated by pushrods running in anti-noise ball-bearings, and use automatic connections at the assembly joints. The rudder is actuated by stainless cables which run in polyamid tubings.
Infinitely variable trim, lockable by a stick key.
All control surface hinges of the wing and of the horizontal tail unit use needle bearings or low-maintenance plastic bearings. The actuating levers and bellcranks are fitted with ball bearings and precise uniball-joints. This provides the lowest possible actuating forces for the pilot and guarantees comfortable, non-fatiguing flying. The fittings are welded steel and milled or turned duraluminium respectively.
OPTIONAL RESCUE SYSTEM
For the ASW-28, the installation of a sailplane rescue system is planned. A large parachute is pulled out by a rocket or pushed out by a mortar which will be actuated either by the pilot or an automatic system after a major part breaks off from the sailplane. The whole sailplane including pilot is brought down slowly in a nose down attitude and the fuselage nose absorbs the impact energy so that the pilot is not hurt. The rescue system saves time and altitude compared to a conventional back pack parachute and will allow rescue saves from lower heights. A rescue system weighs more than a back pack parachute. The latter however is no longer necessary so that a more comfortable and crashworthy back rest can be installed. This allows for taller pilots in the cockpit as well.
Model ASW 28
Airworthiness substantiation according to JAR-22, category U, and according to the LBA-substantiation-requirements for gliders made from fiber composite materials.
Use: Training and performance flights.
Competition flights in the FAI standard Class.
Cloud flying and semi-aerobatics.
Span Incl. winglets 15.00 m (49.21 ft)
Wing area 10.5 m2 (113.02 ft2)
Aspect ratio 21.43
Fuselage length 6.585 m (21.6 ft)
Cockpit height 0.80 m ( 2.62 ft)
Cockpit width 0.64 m ( 2.10 ft)
Winglet height .5 m (1.64 ft)
Height at the tail unit 1.30 m ( 4.27 ft)
Airfoil center part DU 99-147
Aileron section airfoil DU 147M1
Outer wing airfoil DU 99-147M2
Winglet airfoil DU 99-125
Empty mass Including minimum equipment approx. 235 kg ( 518 lb.)
Flight mass max. 525 kg (1157.4 lb.)
Mass of one wing approx. 60 kg ( 132 lb.)
Wing loading max. 50 kg/m2 ( 10.24 lb/ft2)
Wing loading min. approx. 29 kg/m2 ( 5.93 lb/ft2)
Watterballast max. 210 l (55 US.Gal.)
Useful load max. 130 kg ( 287 lb.)
Useful load in the pilot seat incl. chute max. 115 kg ( 254 lb.)
Max. speed 285 km/h ( 154 kts)
Max. maneuver speed 200 km/h ( 108 kts)
For m = 325 kg flight mass:
Min. speed approx. 70 km/h ( 37.8kts)
Min. sink approx. 0.55 m/s ( 108.3 ft/min)
Best L/D approx. 45 at 92 km/h