A gas turbine engine that includes a compressor and a combustor, wherein the combustor includes a primary fuel injector within a fuel nozzle and a secondary fuel injector upstream of the fuel nozzle, a system for detecting a flame about the secondary fuel injector, the system comprising: a first pressure sensor that detects an upstream pressure upstream of the secondary fuel injector; a second pressure sensor that detects a downstream pressure downstream of the secondary fuel injector; means for determining a measured pressure difference between the upstream pressure and the downstream pressure; and means for comparing the measured pressure difference to an expected pressure difference; wherein the combustor comprises a combustion chamber, and the fuel nozzle comprises a position directly upstream of the combustion chamber; and wherein the expected pressure difference comprises a pressure difference that is expected when there is no flame about the secondary fuel injector; and wherein the means for determining the measured pressure difference comprises a transducer operably connected to detect the pressure difference between the upstream pressure and the downstream pressure; the means for comparing the measured pressure difference to an expected pressure difference comprises a computer-implemented controller; the computer-implemented controller is configured to determine the expected pressure difference via at least one of a) consulting a stored value; and b) calculating by applying an algorithm to parameters of the gas turbine engine and measured operating conditions; and the computer-implemented controller is configured to indicate that there is a flame about the secondary fuel injector in response the difference between the expected pressure difference and the measured pressure difference exceeding a predetermined threshold, wherein the combustor includes a combustor casing, and a cap assembly; the cap assembly is defined, at least in part, at a forward end by an end cover and at an aft end by the fuel nozzle; wherein a fuel line extends through the end cover and the interior of the cap assembly to engage the fuel nozzle; the combustor casing is positioned about the cap assembly such that a combustor casing annulus is formed therebetween; the secondary fuel injector comprises a fuel injector that is configured to inject fuel into the combustor casing annulus; the first pressure sensor comprises a position within the combustor casing annulus and is positioned in the flow annulus (114,119,123,124,126,127) of the combustor and upstream of the secondary fuel injector. a first pressure sensor that detects an upstream pressure upstream of the secondary fuel injector; a second pressure sensor that detects a downstream pressure downstream of the secondary fuel injector; means for determining a measured pressure difference between the upstream pressure and the downstream pressure; and means for comparing the measured pressure difference to an expected pressure difference; wherein the combustor comprises a combustion chamber, and the fuel nozzle comprises a position directly upstream of the combustion chamber; and wherein the expected pressure difference comprises a pressure difference that is expected when there is no flame about the secondary fuel injector; and wherein the means for determining the measured pressure difference comprises a transducer operably connected to detect the pressure difference between the upstream pressure and the downstream pressure; the means for comparing the measured pressure difference to an expected pressure difference comprises a computer-implemented controller; the computer-implemented controller is configured to determine the expected pressure difference via at least one of a) consulting a stored value; and b) calculating by applying an algorithm to parameters of the gas turbine engine and measured operating conditions; and the computer-implemented controller is configured to indicate that there is a flame about the secondary fuel injector in response the difference between the expected pressure difference and the measured pressure difference exceeding a predetermined threshold, wherein the combustor includes a combustor casing, and a cap assembly; the cap assembly is defined, at least in part, at a forward end by an end cover and at an aft end by the fuel nozzle; wherein a fuel line extends through the end cover and the interior of the cap assembly to engage the fuel nozzle; the combustor casing is positioned about the cap assembly such that a combustor casing annulus is formed therebetween; the secondary fuel injector comprises a fuel injector that is configured to inject fuel into the combustor casing annulus; the first pressure sensor comprises a position within the combustor casing annulus and is positioned in the flow annulus (114,119,123,124,126,127) of the combustor and upstream of the secondary fuel injector.