Abstract: An engine driven pump includes a drive apparatus that is assisted into the disengaged condition prior to disconnect by the ported pressure in the pump. A spring-biased actuator assembly is fluidly connected to a depressure valve of the pump, and along with its spring bias, urges a yoke into a disengaged position to disengage the gear faces of the mechanism. A trigger link held by a solenoid plunger normally retains the yoke in an engaged position. A drive socket can be accessed to return the yoke, and hence the gear faces, into the engaged position. The pump can be disengaged under command during flight or when the aircraft is on the ground, and can only be re-engaged when the aircraft is on the ground. The drive apparatus has few rotating components to reduce rotational inertia; and is enclosed within a housing with no exposed components with all parts continually lubricated.