The Schempp-Hirth Nimbus-4 is a family of high-performance FAI Open Class gliders designed by

Klaus Holighaus __NOTOC__ Klaus Holighaus (14 July 1940 – 9 August 1994) was a Glider (sailplane), glider designer, gliding, glider pilot and entrepreneur.Schempp-Hirth Flugzeugbau GmbH in Kirchheim,

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. 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 The aspect ratio of a geometry, geometric shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height, when the rectangl ...

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 give ...

of better than 60:1 at a best glide airspeed of 110 km/h (59

knots A knot is a fastening in rope or interwoven lines. Knot or knots may also refer to: Other common meanings * Knot (unit), of speed * Knot (wood), a timber imperfection Arts, entertainment, and media Films * ''Knots'' (film), a 2004 film * ''Kn ...

), 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 flig ...

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 wikt:configuration, configuration in which the tailplane of an aircraft is mounted to the top of the vertical stabilizer, fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs fr ...

(with fixed

horizontal stabilizer A tailplane, also known as a horizontal stabilizer, is a small lifting surface located on the tail ( empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplan ...

and two-piece

elevator An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems suc ...

). The manufacturing process uses a hand lay-up of composite material plies and

epoxy resin Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also co ...

s. 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 comp ...

/ foam core sandwich 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 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 h ...

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 A cockpit or flight deck is the area, on the front part of an aircraft, spacecraft, or submersible, from which a pilot controls the vehicle. The cockpit of an aircraft contains flight instruments on an instrument panel, and the controls th ...

) 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 as ...

, 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, sta ...

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, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...

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 moderate and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable suppor ...

) 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 Klaus Ohlmann (born 1952 in Neustadt an der Aisch, Germany)) is a German glider pilot who has established 36 world records approved by FAI. Among these is the record for a free distance flight with up to 3 turn-points by flying 3,009 km from Cha ...

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 The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and inci ...

(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 a Federal government of the United States, U.S. federal government agency within the United States Department of Transportation, U.S. Department of Transportation that regulates civil aviation in t ...

(FAA), regarding the accident history of the Nimbus-4DM in conjunction with a 1999 accident near

Minden, Nevada Minden is a census-designated place (CDP) in Douglas County, Nevada, United States. The population was 3,001 at the United States Census 2010, 2010 census. It is the county seat of Douglas County and is adjacent to the town of Gardnerville, Nevad ...

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, mobile ...

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

Fayence Fayence (; ) is a Communes of France, commune in the Var (department), Var Departments of France, department in the Provence-Alpes-Côte d'Azur Regions of France, region in Southeastern France. Fayence is one of a series of "perched villages" ov ...

, France, on 4 September 1994. The second involved a collision with the ground during takeoff in

Fuentemilanos Segovia () is a province of central/northern Spain, in the southern part of the autonomous community of Castile and León. It is bordered by the province of Burgos in the north, Soria in the northeast, Guadalajara in the east, Madrid in the south, ...

, 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 ed ...

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 (, CIAIAC) is the Spain, Spanish national agency responsible for air accident investigation. It is a division of the Ministry of Public Works and Transport (Spain), Ministry of Pub ...

, 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 competitions, gliding competition held roughly every two years by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are always held in the sum ...

in New Zealand in 1995, a Nimbus-4 (owned by the

French Air Force The French Air and Space Force (, , ) is the air force, air and space force of the French Armed Forces. Formed in 1909 as the ("Aeronautical Service"), a service arm of the French Army, it became an independent military branch in 1934 as the Fr ...

) 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 In aviation, V-speeds are standard terms used to define airspeeds important or useful to the operation of all aircraft. These speeds are derived from data obtained by aircraft designers and manufacturers during flight testing for aircraft Type ...

" 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