Assembly comprising a fluid pressure actuating system, a mechanical balancing device and a locking assembly; the actuating system including first fluid-pressure connecting means to a first fluid-pressure network and second fluid-pressure connecting means to a second fluid-pressure network, the first fluid-pressure network being independent from the second fluid-pressure network and both networks being connected to the mechanical balancing device; the actuating system having at least a first actuator and a second actuator, the first fluid-pressure connecting means being linking and feeding the first actuator with fluid-pressure from the first fluid-pressure network, while the second fluid-pressure connecting means being linking and feeding the second actuator with fluid-pressure from the second fluid-pressure network; the first actuator and the second actuator being mechanically linked to cooperate for displacing at least a first common output member and a second common output member between two extreme control positions; the first and second actuators including respectively a first and second movable piston (3; 4) each severing a first and second extraction fluid-pressure chamber (6a; 7a) and a first and second retraction fluid-pressure chamber (6b; 7b), characterized in that for the mechanical balancing device to provide flexible / continuous force fight compensation for respective first and second actuators (1; 2), the mechanical balancing device includes, for each of first / second - extension / retraction chambers (6a-b; 7a-b) of the first and second actuators (1; 2), one dedicated fluid-pressure commanded balance valve; a first balance valve being commanded by the individual fluid pressure in chamber to balance fluid-pressure from the first fluid-pressure network to a given extension fluid-pressure chamber of the first actuator, is rigidly coupled by a corresponding coupling rod to a cooperating second balancing valve balancing fluid-pressure from the second fluid-pressure network to a given extension fluid-pressure chamber of the second actuator; while a third balancing valve commanded by the individual fluid pressure in chamber to balance fluid-pressure from the first fluid-pressure network to a given retraction fluid-pressure chamber of the first actuator, is rigidly coupled by another corresponding coupling rod to a cooperating fourth balancing valve balancing fluid-pressure from the first fluid-pressure network to a given retraction fluid-pressure chamber of the second actuator; each fluid-pressure commanded balance valve being arranged to allow relief of differential pressure, directly into a dedicated return pressure relief line of the associated first fluid-pressure network or the associated second fluid-pressure network; a locking assembly cooperating with the mechanical balancing device and includes, for each of a pair of first / second balance valves and third / fourth balance valves, a fluid-pressure controlled locking device, each locking device having first and second retainer pins (26a, 26b) adapted to engage with the corresponding coupling rods (16a, 16b) thus inhibiting the corresponding pair of first / second balance valves and third / fourth balance valves, in case of loss of fluid-pressure in one of the first fluid-pressure network or the associated second fluid-pressure network.