Hydraulic failsafe system and method for an axisymmetric vectoring nozzle

A failsafe nozzle actuating system for an aircraft gas turbine engine comprising:

• a variable thrust vectoring axisymmetric exhaust nozzle having a plurality of multi-degree of freedom pivotal flaps circumferentially disposed about a nozzle centerline and bounding an exhaust gas flowpath in said nozzle,
• said pivotal flaps being differentially pivotal so as to have different attitudes about said nozzle centerline in a vectored configuration of said nozzle,
• a primary nozzle actuating means operably connected to said flaps for pivoting and setting an attitude for each of said flaps relative to the centerline,
• said primary nozzle actuating means including primary actuators,
• each of said actuators being extendable independent of any other of said primary actuators between a fully extended position and a fully retracted position,
• a failsafe nozzle actuating means operably connected to said flaps for pivoting and setting a failsafe attitude of said flaps,
• said failsafe nozzle actuating means including failsafe actuators each of which is extendable to a failsafe position corresponding to a position for pivoting and setting each of said flaps to a failsafe attitude, and
• a failsafe control system operable to set said flaps at said failsafe attitude during a failsafe mode of said nozzle actuating system wherein said failsafe attitude of each of said flaps is one at which each of said primary actuators is at a partially retracted position between said fully extended position and said fully retracted position of said primary actuators.