US 5,490,379 AGranted

Fuel metering unit

AssigneeWoodward Governor Company

InventorsDonald E. Wernberg, Gregory A. Molenaar, Daniel F. Miller

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Abstract

A fuel metering unit for an aircraft gas turbine engine has both electronic and manual control, both compensated for altitude variations. A three-dimensional cam is used to control the position of a fuel metering valve. One axis of the 3-D cam is electronically controlled and another is mechanically controlled. Electronic control is the normal mode and sets the electronic axis to provide a fuel metering valve setting which delivers a mass flow rate to the engine as demanded by the position of the fuel lever as interpreted by the electronic control. Upon failure of the electronic control, the position of the 3-D cam along the electronic axis is mechanically locked so that any further changes in fuel metering valve position are a function solely of the position of the power lever as translated to the mechanical axis of the 3-D cam. Transfer from electronic to manual control is therefore "bumpless."

Claims19

Dependent claims

A fuel metering unit for an aircraft gas turbine engine having both electronic and manual controls, the fuel metering unit comprising, in combination:

a supply inlet connected to receive fuel at an elevated pressure from a fuel supply, a metered outlet connected to the engine for providing metered fuel flow thereto, a bypass outlet for returning excess fuel flow to the supply;
a fuel metering valve connected between the inlet and the metered outlet for metering the outlet;
a bypass valve for maintaining a substantially constant pressure drop for the fuel metering valve;
a 3-dimensional (3-D) cam having a complex surface for driving a follower to control the fuel metering valve, the three-dimensional cam having one control axis adapted for manual control and another control axis adapted for electronic control;
mechanical means coupling a power lever to the cam for adjustment along the manual control axis to provide manual fuel control;
an electrical actuator coupling the electronic control to the cam for adjustment along the electronic control axis for providing electronic fuel control;
and detent means providing a holding force for locking the actuator in position upon transfer from electronic to manual control thereby to accomplish said transfer without causing a transient in fuel valve position.

4 more elements

Dependencies are inferred from the claim text.