The Schempp-Hirth Nimbus-4 is a family of high-performance

FAI Open Class Competition classes in gliding, as in other sports, mainly exist to ensure fairness in competition. However the classes have not been targeted at fostering technological development as in other sports. Instead classes have arisen because of: * ...

gliders designed by Klaus Holighaus and manufactured by Schempp-Hirth Flugzeugbau GmbH in Kirchheim,

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

. The Nimbus-4 first flew in 1990.

Design and development

The Nimbus-4 family is a direct derivative of its predecessors at the highest performance end of the Schempp-Hirth product range, the Nimbus-2 and Nimbus-3. In total , 44 single-seat and 100 two-seat models have been produced. The wing taper varies along the span, which is increased to 26.5 metres. The aspect ratio is 38.8. The fuselage is also lengthened and a larger rudder fitted. The manufacturer claims this glider has a

glide ratio In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under giv ...

of better than 60:1 at a best glide airspeed of 110 km/h (59 knots), meaning it can glide over 60 kilometres on course for every 1000 metres of altitude lost in still air. There is a two-seat version, the 4D, and

motor glider A motor glider is a fixed-wing aircraft that can be flown with or without engine power. The FAI Gliding Commission Sporting Code definition is: a fixed-wing aerodyne equipped with a means of propulsion (MoP), capable of sustained soaring flight ...

versions with either turbo engines (designation T) or self-launching engines (designation M).

Nimbus-4DM

The Nimbus-4DM is typical of the Nimbus-4 design, except for variations in cockpit and powerplant configuration and associated operating limitations. It is a 2-seat, high-performance motorized glider, constructed from fiber reinforced plastic (FRP) composites, featuring full span flight controls and a

T-tail A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane ...

(with fixed horizontal stabilizer and two-piece

elevator An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They a ...

). The manufacturing process uses a hand lay-up of composite material plies and epoxy resins. The wing's 26.5-meter (87-foot) span consists of three sections per side, consisting of a

wing tip A wing tip (or wingtip) is the part of the wing that is most distant from the fuselage of a fixed-wing aircraft. Because the wing tip shape influences the size and drag of the wingtip vortices, tip design has produced a diversity of sha ...

, outboard section, and inboard section. The inboard sections mate at the fuselage and the outer wing sections mate with the inboard sections approximately 12.6 feet outboard of the fuselage root chord. The wing shells are a

carbon fiber Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...

foam core sandwich Foams are materials formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the r ...

construction with one main spar constructed of a

glass fiber Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...

/foam core shear web and carbon fiber

spar SPAR, originally DESPAR, styled as DE SPAR, is a Dutch multinational that provides branding, supplies and support services for independently owned and operated food retail stores. It was founded in the Netherlands in 1932, by Adriaan van Well, ...

flanges. A single-vane

flap Flap may refer to: Arts, entertainment, and media * ''Flap'' (film), a 1970 American film * Flap, a boss character in the arcade game ''Gaiapolis'' * Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland'' Biology and he ...

spans the entire inboard wing section. Three sections of

ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

(that is, inboard, center, and outboard) span the outboard wing section with a fourth aileron, used to minimize the effects of adverse yaw, attached to the wing tip. The forward fuselage ( cockpit) is constructed of

Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...

, carbon and glass fiber laminate, reinforced by a double skin on the sides with integrated surrounding canopy frame and seat pan mounting flanges. The single-piece canopy hinges sideways and opens to the right. The aft fuselage section is constructed of a pure carbon fiber monolithic shell, stiffened by carbon fiber/foam core bulkheads and glass fiber webs. The horizontal stabilizer is constructed of glass fiber/foam core sandwich with carbon fiber reinforcements. The elevator halves are a hybrid composite (carbon and glass fiber) monolithic shell. The

vertical stabilizer A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, s ...

is carbon fiber/foam core sandwich construction. The single-piece

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...

is constructed of glass fiber/foam core sandwich. The flight controls are all push/pull tubes except for the rudder, which is controlled via cables. The Nimbus-4DM is powered by a liquid-cooled 44 kW Bombardier Rotax 535C engine with a 3:1 belt

reduction drive A reduction drive is a mechanical device to shift rotational speed. A planetary reduction drive is a small scale version using ball bearings in an epicyclic arrangement instead of toothed gears. Reduction drives are used in engines of all kinds ...

. The powerplant is housed in the fuselage immediately aft of the wing. An electrically driven spindle drive (

jackscrew A jackscrew, or screw jack, is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderately and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable supp ...

) extends the propeller pylon upwards and forward from the engine bay. When stowed, two doors mounted to the rear fuselage conceal the powerplant. The jackscrew is attached between the airframe and the upper forward end of the pylon such that when the jackscrew is retracted (shortened) the pylon is pulled upwards and forward into its flight position. A 4DM holds the world record for speed over a 500 km course - 306.8 km/h (190.6 mph) which is in excess of its V_NE. It was flown by Klaus Ohlmann and Matias Garcia Mazzaro on 22 December 2006.Open class glider: speed over an out-and-return course of 500km
/ref>

Accident history

U.S. National Transportation Safety Board (NTSB) investigators queried the German

Luftfahrt-Bundesamt The ''Luftfahrt-Bundesamt'' (LBA, "Federal Aviation Office") is the national civil aviation authority of Germany headquartered in Braunschweig.Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...

(FAA), regarding the accident history of the Nimbus-4DM in conjunction with a 1999 accident near Minden, Nevada where both occupants of the aircraft were killed. In this accident, the glider broke up in flight during the recovery phase after a departure from controlled flight while maneuvering in

thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobil ...

conditions. Airborne witnesses in other gliders who saw the beginning of the accident sequence said the glider was in a tight turn, as if climbing in a thermal, when it entered a spiral. With a 45-degree nose-down attitude, the speed quickly built up as the glider completed two full rotations. The rotation then stopped, the flight stabilized on a northeasterly heading, and the nose pitched further down to a near-vertical attitude (this is consistent with the spin recovery technique specified in the Aircraft Flight Manual (AFM)). The glider was observed to level its attitude, with the wings bending upward and the wing tips coning higher, when the outboard wing tip panels separated from the glider, the wings disintegrated, and the fuselage dived into the ground. Several witnesses estimated that the wing deflection reached 45 degrees or more before the wings failed. Examination of the wreckage disclosed that the left and right outboard wing sections failed symmetrically at two locations. In this case, the NTSB determined "that the probable cause of this accident was the pilot's excessive use of the elevator control during recovery from an inadvertently entered spin and/or spiral dive during which the glider exceeded the maximum permissible speed, which resulted in the overload failure of the wings at loadings beyond the structure's ultimate design loads." At the time there were three previous accidents worldwide on file with the

Federal Bureau of Aircraft Accidents Investigation The German Federal Bureau of Aircraft Accident Investigation
" ''German Federal Bureau of Aircraft Accident Investigation ...

(BFU), Germany's equivalent of the NTSB. The first was a non-injury long landing accident in

Fayence Fayence (; oc, Faiença) is a commune in the Var department in the Provence-Alpes-Côte d'Azur region in Southeastern France. In 2019, it had a population of 5,735. Fayence is one of a series of "perched villages" overlooking the plain betwee ...

, France, on 4 September 1994. The second involved a collision with the ground during takeoff in Fuentemilanos, Spain, on 27 July 1997, which resulted in two fatalities. The improper installation of the horizontal stabilizer led to the third accident in Lüsse, Germany, on 13 June 1999, in which two occupants were injured during an attempted takeoff when the stabilizer separated from the

empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third e ...

just after liftoff. NTSB investigators became aware of another accident involving a Nimbus-4DM that occurred in Spain shortly after the Minden, Nevada, accident. According to the

Comisión de Investigación de Accidentes e Incidentes de Aviación Civil The Civil Aviation Accident and Incident Investigation Commission ( es, Comisión de Investigación de Accidentes e Incidentes de Aviación Civil, CIAIAC) is the Spanish national agency responsible for air accident investigation. It is a division ...

, Spain's equivalent of the NTSB, the glider broke up in flight following a high-speed excursion beyond Vne. According to preliminary information supplied by the Spanish authorities, the pilot stated they were in a turn when a heavy thermal caused the glider to enter a steep descending spiral. The pilot could not recover the aircraft from the spiral and the airspeed quickly exceeded Vne. The pilot then reported that the right wing failed and he bailed out. The BFU has recorded four incidents/accidents with the single-seat versions. Three events are known of non-injury accidents during off-field landings, and one fatal accident was due to collision with a mountain. Additionally, during training for the

World Gliding Championships The World Gliding Championships (WGC) is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern ...

in New Zealand in 1995, a Nimbus-4 (owned by the French Air Force) was destroyed in a midair breakup accident. The glider entered a wave cloud, lost control, and broke up at a speed beyond 400 km/h (The never exceed speed, or " Vne" is 285 km/h, and the design dive speed, or " Vd", is 324 km/h). The pilot survived by bailing out. According to the LBA, "As far as we know, none of the incidents/accidents recorded indicated a technical failure."

Variants

The Nimbus-4DM is a model of the "Nimbus-4 Family," which consists of single-seat and two-seat gliders and motor gliders. The engine in each motor glider retracts into the fuselage, behind the cockpit. The different models are (production data ): * Nimbus-4: a single-seat glider, type certified in Germany January 1, 1994. Total number produced: 11 * Nimbus-4T: a single-seat self-sustaining motor glider, type certified in Germany June 15, 1993. Total number produced: 12 * Nimbus-4M: a single-seat self-launching motor glider, type certified in Germany January 1, 1994. Total number produced: 10 * Nimbus-4D: a two-seat glider, type certified in Germany February 24, 1995. Total number produced: 9 * Nimbus-4DT: a two-seat self-sustaining motor glider, type certified in Germany May 5, 1995. Total number produced: 6 * Nimbus-4DM: a two-seat self-launching motor glider, type certified in Germany November 7, 1995. Total number produced: 37 * Nimbus-4DL: a two-seat glider with extended fuselage for tall people * Nimbus-4DLT: a two-seat self-sustaining motor glider and extended fuselage for tall people * Nimbus-4DLM: a two-seat self-launching motor glider and extended fuselage for tall people

Specifications (4DM unless otherwise specified)

References

External links

Schempp-Hirth's homepage

Movie of Nimbus-4D
{{Italian military aircraft Nimbus-4 1990s German sailplanes Aircraft first flown in 1990 Motor gliders T-tail aircraft