Abstract: Method and apparatus for pumping fuel to jet engines and the like utilizing at least two stages, the first of which is a main stage including a centrifugal pump, together with a secondary stage including a positive displacement pump. The two pump stages are driven from a common drive means. In the new system, the positive displacement pump is used as a startup pump and the centrifugal pump is the sole pumping means employed during conditions of higher fuel demand. Speed responsive means are provided in conjunction with the positive displacement pump, which means are responsive to the speed of the centrifugal pump, the speed responsive means being used to terminate pumping action by the positive displacement upon the centrifugal pump reaching a predetermined speed.

Abstract: A control unit which is particularly useful in controlling the output pressure of a turbocharger in response to the manifold pressure with compensation for pressure drop at the throttle characterized by a reference unit disposed in the housing for the manifold pressure to act on and at least one diaphragm extending across said housing to apply the pressure differential between the manifold pressure and the output pressure of the turbocharger. In one embodiment, the reference unit includes a bellows of a predetermined volume of gas which schedules the displacement of the reference unit in response to the temperatures of the gases of the manifold. Another embodiment includes an additional diaphragm and valve means for applying additional pressures to the reference means to compensate for the altitude for the system to prevent overspeeding of the turbocharger.