| X4 | |
|---|---|
| Role | Experimental four-seat light aircraft Type of aircraft |
| National origin | France |
| Manufacturer | Avions Robin |
| First flight | 25 February 1991 |
| Number built | 1 |
TheRobin X4 was anexperimentalFrench four-seat light aircraft designed and built byAvions Robin to test different wing configurations and construction materials.[1] The X4 was a low-wingmonoplane with atricycle landing gear and powered by a 116 hp (87 kW) Textron Lycoming engine.[1]
Originally designed as a 4-seatATL aircraft, and at the time called the ATL II or ATL.FAR23, it was later intended to become a long-term replacement for theDR.400 series of aircraft.[2] After Pierre Robin soldhis company, the name was changed to X4, X for experimental and 4 for 4-seater; the design was also changed from theATL'sV tail to a more conventionalcruciform type. The fuselage was fibreglass and epoxy in aNomex sandwich, which allowed more fluid curves, and was generally triangular in cross-section, like theMe 262.[3] The landing gear was from a DR.400, and the forward-tilting canopy from anATL.[4][5] The wings were wood and fabric, like those of a standardDR.400, but of constant dihedral; the wooden construction allowed modifications to be made quickly and cheaply.[4] The rudder and ailerons were of metal construction.[4]
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, especiallylaminar flow; the feasibility of producing a composite-material aircraft; and to test new systems (e.g. rod rather than cable controls).[4]
Testing atSaint-Cyr showed a slight advantage to the X4 when compared to the equivalentDR.400/120, despite, according to Müller, its 'tired'[6] 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.[7] However, the improved performance came at the cost of a non-benignstall unsuitable for a training aircraft.[6] 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 theCirrus SR22. The new owners ofAvions Robin were not interested in the design, and it was ultimately scrapped.[6]