Abstract: A fuel system a main manifold with an inlet and a plurality of main manifold branches. Each valve in a plurality of valves is connected in fluid communication with a respective one of the main manifold branches in the plurality of main manifold branches to receive flow from the main manifold. Each secondary manifold in a plurality of secondary manifolds connects a single one of the valves in the plurality of valves to a pair of secondary manifold branches. Each nozzle in a plurality of fuel nozzles includes a first inlet connected in fluid communication to one of the valves through one of the secondary manifold branches, and a second inlet connected in fluid communication to a different one of the valves through a different one of the secondary manifold branches so each of the fuel nozzles has a redundant connection to the main manifold through two of the valves.

Abstract: A method for detecting performance degradation of an AC Nozzle in a gas turbine engine including operating the gas turbine engine under a normal operating condition, maintaining the fuel flow rate at a constant fuel flow rate, determining a delta pressure PDelta-Normal across an N number of Proportional Metering Valves (PMVs) as the gas turbine engine is operating under the normal operating condition, selecting a PMV and an AC Nozzle, controlling the PMV to modify a fuel flow rate to the selected AC Nozzle to cause the gas turbine engine to operate under a modified fuel flow condition, determining a delta pressure PDelta-Modified across the N number of PMVs as the gas turbine engine is operating under the modified operating condition and comparing the delta pressure PDelta-Normal with the delta pressure PDelta-Modified to determine if the selected AC Nozzle is uncalibrated or has failed.

Abstract: A fuel system a main manifold with an inlet and a plurality of main manifold branches. Each valve in a plurality of valves is connected in fluid communication with a respective one of the main manifold branches in the plurality of main manifold branches to receive flow from the main manifold. Each secondary manifold in a plurality of secondary manifolds connects a single one of the valves in the plurality of valves to a pair of secondary manifold branches. Each nozzle in a plurality of fuel nozzles includes a first inlet connected in fluid communication to one of the valves through one of the secondary manifold branches, and a second inlet connected in fluid communication to a different one of the valves through a different one of the secondary manifold branches so each of the fuel nozzles has a redundant connection to the main manifold through two of the valves.

Abstract: In accordance with at least one aspect of this disclosure, a method can include controlling firing of an exciter of an engine with an electronic controller separate from the exciter as a function of at least one excitation command from the electronic controller and at least one feedback signal from the exciter operatively connected to the electronic controller.

Abstract: An engine ignition system can include a multifunction controller, and an exciter operatively connected to the multifunction controller. The multifunction controller can be configured to control the exciter to output an ignition voltage. The multifunction controller can be configured to perform at least one other engine control function.