The Robin X4 was an

experimental An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...

French French may refer to: * Something of, from, or related to France ** French language, which originated in France ** French people, a nation and ethnic group ** French cuisine, cooking traditions and practices Arts and media * The French (band), ...

four-seat light aircraft designed and built by

Avions Robin Robin Aircraft is a French manufacturer of light aircraft. It succeeds to ''Centre-Est Aéronautique'', ''Avions Pierre Robin'' and Apex Aircraft (''Avions Robin'' and ''Robin Aviation''). History Centre-Est Aéronautique was formed by Pierre ...

to test different wing configurations and construction materials. The X4 was a low-wing

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple wings. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

with a

tricycle landing gear Tricycle gear is a type of aircraft undercarriage, or ''landing gear'', that is arranged in a tricycle fashion. The tricycle arrangement has one or more nose wheels in a single front undercarriage and two or more main wheels slightly aft of th ...

and powered by a Textron Lycoming engine.

Design and development

Originally designed as a 4-seat ATL aircraft, and at the time called the ATL II or ATL. FAR23, it was later intended to become a long-term replacement for the DR.400 series of aircraft. After Pierre Robin sold his company, the name was changed to X4, X for experimental and 4 for 4-seater; the design was also changed from the ATL's V tail to a more conventional

cruciform A cruciform is a physical manifestation resembling a common cross or Christian cross. These include architectural shapes, biology, art, and design. Cruciform architectural plan Christian churches are commonly described as having a cruciform ...

type. The fuselage was fibreglass and epoxy in a

Nomex Nomex is a trademarked term for an inherently flame-resistant fabric with meta-aramid chemistry widely used for industrial applications and fire protection equipment. It was developed in the early 1960s by DuPont and first marketed in 1967. ...

sandwich, which allowed more fluid curves, and was generally triangular in cross-section, like the

Me 262 The Messerschmitt Me 262, nicknamed (German for "Swallow") in fighter versions, or ("Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the German aircraft manufacturer Messersc ...

. The landing gear was from a DR.400, and the forward-tilting canopy from an ATL. The wings were wood and fabric, like those of a standard DR.400, but of constant dihedral; the wooden construction allowed modifications to be made quickly and cheaply. The rudder and ailerons were of metal construction. It first flew on 25 February 1991, with Robin head of development Daniel Müller at the controls; whilst designed as a four-seater, only the front two seats were installed with the rear being taken up with test equipment. The airframe was used to test various wing profiles, especially

laminar flow Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...

; the feasibility of producing a composite-material aircraft; and to test new systems (e.g. rod rather than cable controls). Testing at Saint-Cyr showed a slight advantage to the X4 when compared to the equivalent DR.400/120, despite, according to Müller, its 'tired' engine. For example, optimisation of the cowling reduced engine cooling drag by 20%, or 5% of global drag; in total there was a 25 km/h gain in cruise speed. However, the improved performance came at the cost of a non-benign stall unsuitable for a training aircraft. According to Robin and Besse, the airframe was capable of eventually being a whole series up to 4+2 seat configuration with correspondingly larger engines, and be a potential competitor to the

Cirrus SR22 The Cirrus SR22 is a single-engine four- or five-seat composite aircraft built since 2001 by Cirrus Aircraft of Duluth, Minnesota, United States. It is a development of the Cirrus SR20, with a larger wing, higher fuel capacity and more powerfu ...

. The new owners of

were not interested in the design, and it was ultimately scrapped.

Variants

;Robin X4 :Lycoming 116hp O-235N engine, registration F-WKQX; one built; voluntarily destroyed

References

;Notes ;Bibliography *Besse, Francois ''La Saga Robin (de 1957 à nos jours)''. Mayenne: Jouve, 2012. *Lambert, Mark ''Jane's All the World's Aircraft 1994-95''. Coulsdon: Jane's Information Group, 1994. *Masse, Xavier ''Avions Robin (du Jodel-Robin de 1957 au DR.500 de 2000)''. Paris: Nouvelles Editions Latines, 2000. {{Robin aircraft 1990s French experimental aircraft X-4 Low-wing aircraft Single-engined tractor aircraft Aircraft first flown in 1991 Aircraft with fixed tricycle landing gear Single-engined piston aircraft