Lock mechanism

A lock for use in a thrust reversal system of a gas turbine engine, the thrust reversal system including a member movable between a stowed position and a deployed position under the control of a thrust reversal system controller, the lock comprising a first locking device having a first operator and including a first locking member movable between an open position and a locked position in which the first locking member cooperates with the thrust reversal system to retain the movable member of the thrust reversal system in its stowed position, a second locking device having a second operator operable independently of said first operator and including a second locking member movable into engagement with said first locking member to secure said first locking member in said locked position wherein said second locking member is movable into an opening formed in said first locking mender, said second operator including a piston slidable within a cylinder, said piston adapted to be coupled to said second locking member, resilient means biasing said second locking member to engage within said opening and control means for controlling a fluid pressure applied to said piston such that in one setting of the control means, the fluid pressure applied to said piston exerts a force on said piston to supplement the force exerted on said piston by said resilient means and in another setting of said control means, the fluid pressure applied to said piston exerts a force on said piston to withdraw said second locking member from said opening.