The new Nimbus -4DL - more space safety and comfort.
By extending the cockpit section of the fuselage and by moving the rear seat aft there is now substantially more space in the all new cockpit, offering ergonomically designed seats for pilots as tall as 2 metres on both seats! At the same time adjustable backrests and pedals allow for comfortable seating of smaller pilots as well. In order to reach this goal extensive computer simulations with a large number of persons with different sizes were performed. As are result control levers and seats have now been placed according to ergonomic criteria and customers requests. The front instrument panel is now designed to tilt up to improve the ease of getting in and out as well as to allow for an easier emergency exit. The larger backwards extended canopy improves the view for the pilot in the rear seat and thus enhances safety. A newly designed canopy frame now seals the cockpit perfectly under all conditions. A maximum of safety, ergonomically use, and comfort is the result of our improvements
This model upgrading – together with the unmatched performance - guarantees that the Nimbus-4DL represents the pinnacle of the Open Class glider constructions.
The NIMBUS-4D is a high-performance two-seat sailplane, constructed from fiber reinforced plastic, and, with a wing span of 86.94 ft (26,5 m, aspect ratio 39.1), is the largest aircraft so far produced in series by Schempp-Hirth.
With a best L/D of about 1:60 and outstanding abilities at low speed and in circling flight, the NIMBUS-4D is a match for the comparable single seaters, but possesses distincly improved flight handling. Both its harmony of controls and maneuverability convey the impression of a considerably smaller two-seater - a result which could only be achieved by the extraordinary aerodynamic design of the wing, combined with an elaborate control system.
Hence the most significant feature of this super two-seat sailpane is - apart from its span - its still unconventional multi-stage swept-back wing leading edge (as also used on the DISCUS and VENTUS-2), the aerodynamic advantages of which are even more enhanced by the dihedral of the wing tips. This wing concept guarantees a perfect utilization of the span and also offers outstanding low speed handling qualities.
The wing (six pices for easier rigging) has full span camber-changing flaps and double-panel Schempp-Hirth type airbrakes on the upper surface of the inboard panels.
The ailerons of the outboard wing panels are superimposed on the flaps. The flaps on the inboard panels are interconnected to the airbrakes, thus permitting steeper approaches at only minor increases in speed: That is to say when extending the airbrakes fully, the already positive deflection of the inboard flaps is automatically almost doubled.
During the take-off and landing run there is only a minor flexing of the wing, thus reducing the danger of unitentionally contacting the ground.
Should the NIMBUS-4D be flown by one person only or in the case that the maximum permitted all-up mass is not reached, then water ballast may be carried in the outboard wings - the total capacity of their integral tanks is 43.4 US Gal. (36.1 IMP Gal. | 164 Liter). The water dump valves hook up automatically on rigging the wing panels.
A very significant simplification of this two-seater's rigging process is the automatic hook-up of the controls betweenfuselage and inboard wing panels, which, once it had been made standard on the VENTUS, DISCUS and DUO DISCUS,was repeatedly requested for the new high-performance two-seaters as well.
Thanks to this innovation, the actuation of various quick-connectors, hardly accessible at the wing-to-fuselage joint and thus no longer justifiable, is now avoided, including their even more difficult securing as required by the LBA.
Only one single ball and swivel joint quick disconnect fitting is retained for the aileron on each outboard wing. Its point of connection is eqsily reached. Rigging this two-seat sailplane (empty mass approx. 1135 lb | 515 kg) is quickly done by three people when using a wing stand.
The construction method of the fuselage shell is sophisticated and involves the use of a mix of materials: While tailboom and fin consist of a carbon fiber lay-up (for less weight and higher buckling strength), the cockpit section is made of a combination of aramid, carbon and glass fiber with various reinforcing stringers and stiffeners (for improved protection of the crew).
Load test of this combination (carried out on a cockpit of the single-seater NIMBUS-4) have demonstrated a distinctly higher safety margin than required by construction regulations. A special design feature, which also characterizes the sturdiness of the fuselage, is its steel tube center frame, taking directly the loads between wing, fuselage and landing gear without stressing the fuselage shell.
The main wheel (tire size 6.00x5) features a hydraulic disc brake. For retracting the wheel, assistance can be given by the occupant on the rear seat. The wheel brake may be actuated by a lever on the control sticks or by extending the airbrakes fully.
For winch launching and aerotow, individual TOST release mechanisms will be provided. The one-piece canopy (no transverse beam!) hingest sideways and features a proven jettisoning mechanism.
Both seats are very comfortable (with head rest and seat pan designed to meet the latest safety requirements) and offer, besides an excellent field of vision, sufficient space on long flights, even for tall pilots. Adjustable rudder pedals (also in flight) are standard for either seat.
The instrument panels are designed to make mainly modern small instruments and indicators (2¼''), thus permitting an easy cockpit entry and exit.
The main control elements are provided in duplicate.
To compensate the nose-heavy moment of loads on the aft seat and/or of water ballast in the outboard wings, a fin tank is available on request, the water dump valve of which is linked to those of the wing tanks, so that all ballast tanks are emptied simultaneously.