Robin X4

The Robin X4 was a one-off experimental French four-seat light aircraft, built by Avions Robin as a flying test bed for different wing configurations and construction materials. It began life as a four-seat design called the ATL II, or ATL.FAR23, and was renamed X4 after Pierre Robin sold his company, the X standing for experimental and the 4 for four seats. Compared with the ATL it dropped the V tail for a more conventional cruciform tail. The fuselage was fibreglass and epoxy in a Nomex sandwich, while the wings were wood and fabric like those of the DR.400, a choice that let the team change the wings quickly and cheaply. A single 116 horsepower Textron Lycoming engine powered it, and it first flew on 25 February 1991 with Robin's head of development, Daniel Müller, at the controls. Only the front two seats were fitted, the rear being used for test equipment. The airframe was used to try laminar flow wing profiles, composite construction and rod controls in place of cables, and trials at Saint-Cyr showed a small speed gain over the DR.400/120, at the price of a stall unsuitable for a training aircraft. The new owners of Avions Robin had no interest in the design and the only example was eventually scrapped.