The Chalwyn TMZ Bendix type automatic valve and D-AMZ Spindle valves utilize two automatic closure methods. They are designed to automatically stop an engine by closing down the air intake in the event of an engine runaway or overspeed condition. These valves incorporate a failsafe loss of pressure override mechanism that will also close the valve automatically with the loss of oil or pneumatic pressure signal from the engine control system. A manual start override/emergency stop lever is also included.