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 easily 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.
The planform of the horizontal tailplane (fixed stabilizer
with elevator) resembles the elegant geometry of the wing. The elevator
hooks up automatically on rigging the tailplane. The elevator trim is adjustable
in fine stages.
The rudder is a GFRP-sandwich construction with integrated
VHF-antenna.
Technical Data and Performances
for Nimbus 4D
| Wing span |
26.50 m |
86.94 ft |
| Wing area |
17.96 m² |
193.32 ft² |
| Wing aspect ratio |
39.1 |
39.1 |
| Empty mass |
515 kg |
1135 lb |
| Max. all-up mass |
750 kg |
1653 lb |
| Wing loading |
32.6-41.8 kg/m² |
6.7-8.6 lb/ft² |
| Max. Speed |
285 km/h |
154 kt | 177 mph |
| Best L/D (at 110 km/h |59 kt | 68 mph) |
~ 60 |
~ 60 |
Top of Page
or
Back to the M&H Soaring
/ Schempp-Hirth Page
