Duo Discus XL

The second step of the Duo Discus X  to the Duo Discus XL improvement 

The Duo Discus XL differs from the duo Discus X particularly by the 10 cm longer cockpit and the associated optimization of seat comfort, security, space and ergonomics. The improved effectiveness of the airbrake system (the airbrakes moved 4cm to the leding edge and are now 18mm higher) makes it now possible to approve the Discus XL  for simple aerobatics including spinning. It's now possible to fly from the back seat without any operating handicaps. These features extend significantly the spectrum of use. The room in the cockpit was additionally increased by extending the rear seat backwards. Further it was possible for or us to improve the operability and effectiveness of the airbrake system. In the Duo Discus XL-Cockpit it is now possible for the pilots taller than 2 m body size to have a comfortable seat as well. The effective adjusting possibilities at the backrests and pedals also improve the seat comfort for the small pilots. Furthermore the front instrument panel is now designed to tilt up to improve the ease of getting in and out as well as an emergency exit. The control levers are placed according to ergonomic criteria and customers requests, and were arranged in optimal position with functional design. There are many surprising solutions, like the changed water valve lever. These will you probably only notice during your first flights. Extensive computer simulations in planning and innumerable persons of different sizes were necessary to place a seat in the cockpit, to maximize the improvement of operation and seat comfort. The backwards extended canopy improves the view for the pilot in the rear seat and is a win for safety in flying. 

The Duo Discus X now has a more perfect successor which ideally combines flight performance, safety and comfort.

The first step of the Duo Discus to the Duo Discus X improvement

On spring 2005, Dipl.-Ing. H.Treiber und Dipl.-Ing. C. Wannenmacher on the backseat made the first flight with the new Duo Discus "x". So one of the most successful sailplanes of the last ten years received an impressive and highly anticipated upgrade which completely fulfilled our expectations in flight. The well known harmonised and impressive flight characteristics were the basis for the improvements and modifications. Our ambition was to top these attributes with the new Duo Discus "x". The following features were realized in this aircraft.

Undercarriage

A new undercarriage was designed, incorporating a total shock distance of about 100 mm (3.94 in.) which significantly increases the energy absorption of the undercarriage. The roll comfort is greatly increased through the soft cushioning and the touchdown shock on landing is remarkably reduced. The total construction height is however still low so that a comfortable entry into the cockpit is possible furthermore. Further advantages of the new undercarriage are:

• Lower lift-off airspeed due to increased angle of attack during take-off roll.
• Light operational force during extension/retraction due to gas strutassistance.
• Undercarriage can be operated and locked from the rear seat.
• Further ease of ground handling due to light tail weights.· Improved off field landings due to higher undercarriage and wider opening doors.
• Robust and maintenance friendly undercarriage construction.

Airbrake System

Because of an aerodynamic work of art - with extension of the airbrakes, a trailing edge flap extends downwards simultaneously - there are multiple advantages during practical flight:

• The loss of aerodynamic lift when the airbrakes are extended is retained with the trailing edge flap (so that the lift coefficient practically remains unchanged) though at the same time the total drag of the aircraft is increased. This allows a steeper approach angle and also - which is very important - a slower landing speed with extended airbrakes and trailing edge flaps.
• The extended trailing edge flaps increase the longitudinal pitch which results in even better visibility to the landing point.
• As the trailing edge flaps and airbrakes are mechanically coupled, the trailing edge flaps react in opposition to the airbrakes upon extension. A non locked airbrake can therefore not extend itself which prevents the situation of taking off with extended airbrakes unintendedly.· No additional work load for the pilot as there is no extra lever needed to operate the trailing edge flaps - they work in unison with the air brakes.

Winglets

The high class aerodynamic wing of the Duo Discus "x" was further improved through the most advanced calculations by Prof. Dr. Karl-Heinz Horstmann and Prof. Dr. M. Maughmer. The performance improvements stretch across the entire usable cross country range though the reduction of the minimum sink rate shows the greatest improvement. This is also evident in increased cruise speeds at all thermal strengths. The harmonic shape of the winglets added to the already optimal wing planform, further increase not only the elegant silhouette of the Duo Discus "x" but also the quality of circling in narrow thermals with high bank.