ASW 27 B - winning made easy
Right from the start the ASW 27 was developed with the interests
of competition pilots in mind. Future engine retrofits or later wingspan increases were specifically ruled out – the goal
was to produce the worlds best performing racing class glider.
Freed from such performance limiting compromises the Schleicher design team developed a brand new aircraft
as a successor of the famous ASW 20. Now the job is completed and the ASW 27 B has been tested by many
glider pilots around the world. After winning a string of major competitions and after taking out first and second
place in the recent world championships the verdict is unanimous - the aircraft is the best performing glider in its class.
Hardly any other glider is pushing the limits of composite technology and aerodynamics as far as the ASW 27.
Years of intensive research in close co-operation with leading universities have led to a new airfoil with extremely long laminar airflow.
In fact the turbulator blowholes are not located in the wing but in the flaperons. As far back as 95 % of the lower cord the laminar
airflow is intentionally trapped into turbulent flow to avoid a drag intensive separation bubble.
Because good low speed performance and high glide ratios are best achieved by high aspect ratios the ASW 27 B
features an aspect ratio of 25 - a world first for a 15m glider. (By comparison, the aspect ratio of the ASW 20 is 21.4)
But that is not all, in the interest of minimizing interference drag late design modifications were made to the inner wing section
which have proved successful in preventing flow separations at high angles of attack. In view of lower Reynolds-numbers near the
wingtip the outer airfoil and the new 0.45 m long winglets were optimized after extensive testing - both in wind tunnels and during
flight comparisons. These important refinements have made key contributions to outstanding aerodynamics and explain the brilliant
high speed glide on one hand and the equally good climb performance on the other.
But let the current world champion John Coutts be the judge. After winning the world championship he stated that he instantly felt
at home in the ASW 27 B and that the aircraft achieves an incredible glide even at speeds as high as 110 kt. Does this explain why the
ASW 27 B is widely regarded as an aerodynamic work of art?
Photo: Bernhard Eckey
NEW FIBER COMPOSITE TECHNOLOGY
Making full use of today’s composite technology has resulted in a number of major benefits. For example, the weight of the wing was reduced
to just 58 kg which in turn allows wing loadings between 33 and 55.6. Maximum pilot weight was increased to 115 kg and the total useful load
lifted to 130 kg. Two water tanks in the wing plus a further 35 liter tank in the fuselage enable the ASW 27 B to carry more water ballast than any
other 15 m glider and also give it the widest range of wing loadings. But more on that later.
The new super strength - yet at the same time very light - polyethylene fibers used in the fuselage account for the low empty mass of 245 kg.
But not only that, the high energy absorption in a mixed laminate with carbon and polyethylene fiber further increases passive safety for the ASW 27 B pilot despite
of the lower structural weight. And by the way, there is also a SL (Super Light) version available weighing even 15 kg less.
After especially formulated resins for water ballast tanks became available the aircraft was modified and re-released as ASW 27 B.
It now includes integrated water ballast tanks with automatic control connections as well as refined winglets. Filling the 155 liter of wing ballast is facilitated
through “concealed” drain outlets on the underside of the wings. To ensure safe take offs with partial water ballast the tanks are separated into two
compartments per wing. Due to a clever wing design the ballast is located almost on the C of G line. Although this eliminates the need for a ballast
tank in the fin it is possible to integrate a fin tank option on request. In addition to wing ballast the ASW 27 B can carry another 35 liters of water in
the fuselage for a total ballast capacity of 190 liter. Best of all, the ASW 27 B retains its superb handling qualities and its pleasant flight characteristics
even when fully ballasted.
COCKPIT AND FUSELAGE
The roomy safety cockpit is another feature of the ASW 27 B. Pilots can only maintain peak performance for any length of time
if they are able to fully relax in a comfortable cockpit. For this reason the ASW 27 B cockpit was designed to accommodate full
size pilots with a bit of spare space for comfort and luggage. Needless to say that all safety features for which designer Gerhard Waibel
received an OSTIV award were fully incorporated. The front hinged canopy with sliding window offers excellent visibility.
Typical for all Schleicher sailplanes the integrated instrument panel hinges upwards with the canopy fully enclosing the instruments.
The integrated gas strut not only ensures low lifting forces but more importantly prevents the canopy from being damaged when blown
shut by a wind gust. In line with the latest safety research the rear section of the canopy frame is especially shaped to allow safe emergency jettison.
Also standard is a pneumatic tail wheel as well as dual releases for aerotow and winch launching. The winch hook is in front of the main wheel
and fully covered by the undercarriage doors when the wheel is retracted. Ample cockpit ventilation is provided by 3 adjustable air intakes
through the aircraft’s nose, the clear vision panel and an airliner style vent on the right cockpit wall. A speed trim integrated into the
control column, the in flight adjustable backs rest, the comfortable seat cushions and the adjustable rudder pedals are some of the many
cockpit features that Schleicher customers have come to expect.
The landing gear is equipped with generous rubber shock absorbers and the big 350x125 tire is connected to a hydraulic disc brake.
An overload weak link is incorporated for occupant protection in case of a very heavy landing and the entire unit is installed in an airtight
undercarriage compartment to avoid drag creating air leakage from the fuselage interior.
HANDLING AND PERFORMANCE
Unmistakable trademarks of Schleicher gliders such as well balanced controls; pleasant handling and extreme control responsiveness are
also hallmarks of the ASW 27 B. No other glider demonstrates better that top performance and docile flying characteristics can go hand in hand
and no other glider can carry large amounts of ballast with ease and still cope well with the narrowest of thermals or extremely turbulent lift.
Landing the ASW 27 B is made easy by a clever control mixer only found in Schleicher gliders. It not only ensures pleasantly low landing speeds
but also guarantees full aileron control until the aircraft has almost come to a complete stop. This control mixer has become a trademark of all
flapped Schleicher gliders and has greatly contributed to the excellent safety record and the first class reputation of the ASW 27 B. And yes; this 48:1
glider can even be enjoyed by pilots with limited fiberglass experience.
But it is mainly the outstanding performance that makes customers respond so well to the ASW 27 B. Sure, a high glide ratio is desirable,
but even more important is a shallow polar curve extending to speeds well above 200 kph. This is where the ASW 27 B really shines.
Its incredible high speed glide has already resulted in a long string of records and the list of first places in competitions is growing longer.
Put simply, the ASW 27 B is for purists with a will to win.
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Photos: Manfred Münch