at a second position 6 b to serve as a backup actuator for actuating the inner aileron of the wing in the event that the hydraulically powered actuator 8 fails the eha 4 b includes an electronically powered hydraulic system including an electrically powered hydraulic pump 10 that provides the hydraulic power for driving the hydraulic actuator 12 of the eha 4 b the eha 4 b is therefore relatively large in size in comparison to the volume of the wing 2 the eha 4 b is bounded by a shear web rib 20 c on either side with a clearance of approximately 10 mm and by an upper and lower composite honeycomb wing skin panel 16 above and below also with a clearance of approximately 10 mm as a result of the introduction of such ehas it can be the case that due to their relatively large size they can fill a significant proportion of the available volume within the trailing edge of the wing where they are positioned as a result of the combination of the limited volume available in the wing and the heat generated by the ehas during use the temperature of the actuator would if not adequately controlled rise as a result of the heat being unable to dissipate effectively into the ambient air thus according to a first embodiment of the invention there is provided a cooling system for cooling the eha 4 b so that its temperature does not exceed operational limits the cooling is effected locally by directing cooling airflow onto the electronic actuator at an area.