A surgical instrument, comprising: a handle assembly configured for operable attachment to a surgical tool assembly; a motor assembly operably supported by said handle assembly at least one rotary drive system (300/320) operably supported by said handle assembly and being configured for selective operable engagement and disengagement with said motor assembly; a bailout system comprising: a bailout drive train supported by said handle assembly and configured for selective operable engagement and disengagement with said at least one rotary drive system; and a bailout actuator assembly selectively movable between a stored position within said handle assembly and an actuation position such that, when said bailout actuator assembly is in said stored position, said at least one rotary drive system is retained in operable engagement with said motor assembly and when said bailout actuator assembly is in said actuation position, said bailout drive train is in operable engagement with said at least one rotary drive system, characterised in that said handle assembly further comprises a bailout access panel that is maneuverable from a closed position wherein said bailout actuator assembly is completely enclosed within said handle assembly in said stored position and an open position wherein said bailout actuator assembly is manually actuatable, and in that the surgical instrument further comprises: a bailout actuator biasing member for biasing said bailout actuator assembly to said actuation position when said bailout access panel is in said open position. a handle assembly configured for operable attachment to a surgical tool assembly; a motor assembly operably supported by said handle assembly at least one rotary drive system (300/320) operably supported by said handle assembly and being configured for selective operable engagement and disengagement with said motor assembly; a bailout system comprising: a bailout drive train supported by said handle assembly and configured for selective operable engagement and disengagement with said at least one rotary drive system; and a bailout actuator assembly selectively movable between a stored position within said handle assembly and an actuation position such that, when said bailout actuator assembly is in said stored position, said at least one rotary drive system is retained in operable engagement with said motor assembly and when said bailout actuator assembly is in said actuation position, said bailout drive train is in operable engagement with said at least one rotary drive system, characterised in that said handle assembly further comprises a bailout access panel that is maneuverable from a closed position wherein said bailout actuator assembly is completely enclosed within said handle assembly in said stored position and an open position wherein said bailout actuator assembly is manually actuatable, and in that the surgical instrument further comprises: a bailout drive train supported by said handle assembly and configured for selective operable engagement and disengagement with said at least one rotary drive system; and a bailout actuator assembly selectively movable between a stored position within said handle assembly and an actuation position such that, when said bailout actuator assembly is in said stored position, said at least one rotary drive system is retained in operable engagement with said motor assembly and when said bailout actuator assembly is in said actuation position, said bailout drive train is in operable engagement with said at least one rotary drive system, characterised in that said handle assembly further comprises a bailout access panel that is maneuverable from a closed position wherein said bailout actuator assembly is completely enclosed within said handle assembly in said stored position and an open position wherein said bailout actuator assembly is manually actuatable, and in that the surgical instrument further comprises: a bailout actuator biasing member for biasing said bailout actuator assembly to said actuation position when said bailout access panel is in said open position.