Robin X4

Role  | Experimental four-seat light aircraft

Type of aircraft

National origin | France
Manufacturer  | Avions Robin
First flight  | 25 February 1991
Number built | 1

The Robin X4 was an experimental French four-seat light aircraft designed and built by Avions Robin to test different wing configurations and construction materials.[1] The X4 was a low-wing monoplane with a tricycle landing gear and powered by a 116 hp (87 kW) Textron Lycoming engine.[1]

## Design and development

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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.[2] 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 type. The fuselage was fibreglass and epoxy in a Nomex sandwich, which allowed more fluid curves, and was generally triangular in cross-section, like the Me 262.[3] The landing gear was from a DR.400, and the forward-tilting canopy from an ATL.[4][5] 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.[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, especially laminar flow; the feasibility of producing a composite-material aircraft; and to test new systems (e.g. rod rather than cable controls).[4]

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'[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-benign stall 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 the Cirrus SR22. The new owners of Avions Robin were not interested in the design, and it was ultimately scrapped.[6]

## Variants

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

## References

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Notes

1. ^ a b Lambert 1994, p. 100
2. ^ Masse 2000, p. 185
3. ^ Besse 2012, p. 168
4. ^ a b c d Masse 2000, p. 187
5. ^ Masse 2000, p. 188
6. ^ a b c Besse 2012, p. 169
7. ^ Masse 2000, p. 189

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. ISBN 0-7106-1160-9
* Masse, Xavier Avions Robin (du Jodel-Robin de 1957 au DR.500 de 2000). Paris: Nouvelles Editions Latines, 2000.

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