This application claims the benefit of European Application EP 18213498.1, filed on Dec. 18, 2018, which is incorporated herein by reference in its entirety.

BACKGROUND

A known aircraft landing gear shock absorber assembly comprises an outer cylinder having a bore which extends partially through the outer cylinder, and a sliding tube slidably coupled within the bore such that an upper end of the sliding tube is retained in the bore and a lower end of the sliding tube projects out of the bore.

In a single axle landing gear assembly the lower end of the sliding tube is provided with an axle to carry one or a pair of wheel and brake assemblies. In a multi axle landing gear assembly the lower end of the sliding tube can comprise a forked yoke or other end fitting arranged to be attached to part of a wheel assembly, such as a bogie beam. Such end fittings as described above will for brevity collectively be referred to as “ground fittings”.

It is known to manufacture a sliding tube and ground fitting separately from one another and then couple them together using one or more mechanical fixings such as nuts and bolts. Such mechanical fixings can include brackets, collars and the like to facilitate a mechanical coupling between the sliding tube on the one hand and the ground fitting on the other hand. While such two part assemblies can result in a cost effective assembly that is simple to manufacture, the weight of the mechanical fixing increases the overall weight of the landing gear assembly.

It is therefore known to instead form the sliding tube and ground fitting as a single piece; for example, machining the sliding tube and axle from a single billet of metal. While this can reduce the weight of the landing gear assembly in comparison to a multi part arrangement as described above, it can increase the cost and complexity of manufacture.

The present inventor has recognised that aircraft landing gear shock absorber sliding tubes can be improved in terms of weight, cost and complexity to manufacture in comparison to known assemblies.

SUMMARY

According to a first aspect of the invention, there is provided an aircraft landing gear shock absorber assembly having: an outer cylinder having a bore which extends into the outer cylinder, the bore defining an opening in the outer cylinder; a sliding tube comprising a first end region slidably coupled within the bore and a second end region which projects out of the opening; a ground fitting distinct from the sliding tube; and a mechanical fixing arranged to mechanically couple the ground fitting to the second end region of the sliding tube. The sliding tube comprises a tubular body portion formed from a ceramic coated fibre composite tube.

Thus, the shock absorber assembly according to the first aspect includes a multiple part sliding tube and ground fitting assembly in which the tubular member of the sliding tube is formed from a fibre composite tube with a ceramic coating defining an outer surface. The present inventor has identified that the ceramic coating of such a tubular member can provide a suitable counter face for the lower bearing of an aircraft landing gear shock absorbing strut outer cylinder. Advantageously, the weight saving provided by the fibre composite element of the sliding tube can be greater than the weight added by the overlapping parts and additional fixings required to enable the ground fitting to be formed separately and mechanically coupled to the sliding tube. Thus, landing gear assemblies according to embodiments of the invention possess the advantages of multi piece design while having the capability of being at least as lightweight as assemblies in which the sliding tube and ground fitting are integrally formed from a single piece of metal. The lightweight nature of the sliding tube can also reduce the unsprung mass in comparison to known assemblies.

Optional features of the shock absorber assembly are set out in the dependent claims.

According to a second aspect of the invention, there is provided an aircraft landing gear assembly including a shock absorber assembly according to the first aspect.

According to a third aspect of the invention, there is provided an aircraft including one or more aircraft landing gear assemblies according to the second aspect.

