A gas turbine engine has a first spool having a low pressure compressor section disposed forward of an air inlet along a direction of travel of the engine, and a low pressure turbine section disposed forward of the low pressure compressor section and drivingly engaged thereto. A second spool has a high pressure compressor section disposed forward of the low pressure compressor section, and a high pressure turbine section disposed forward of the high pressure compressor section and drivingly engaged thereto. The high pressure turbine section is disposed aft of the low pressure turbine section. An output drive shaft drivingly engages the low pressure turbine section and extends forwardly therefrom to drive a rotatable load. A method of operating a gas turbine engine is also discussed.

Aspects of the disclosure generally relate to a turbine engine and method of operating, wherein a change in sealing status can be determined within a cavity between an outer casing and a rotor within the turbine engine. Aspects of the disclosure further relate to a supply of air to the cavity within the turbine engine.

A gas turbine engine having an interdigitated turbine assembly including a first turbine rotor and a second turbine rotor, wherein a total number of stages at the interdigitated turbine assembly is between 3 and 8, and an average stage pressure ratio at the interdigitated turbine assembly is between 1.3 and 1.9. A gear assembly is configured to receive power from the interdigitated turbine assembly, and a fan assembly is configured to receive power from the gear assembly. The interdigitated turbine assembly and the gear assembly are together configured to allow the second turbine rotor to rotate at a second rotational speed greater than a first rotational speed at the first turbine rotor. The fan assembly and the gear assembly are together configured to allow the fan assembly to rotate at a third rotational speed less than the first rotational speed and the second rotational speed. The interdigitated turbine assembly, the gear assembly, and the fan assembly together have a maximum AN.sup.2 at the second turbine rotor between 30 and 90.

A gas turbine engine having an interdigitated turbine assembly including a first turbine rotor and a second turbine rotor, wherein a total number of stages at the interdigitated turbine assembly is between 3 and 8, and an average stage pressure ratio at the interdigitated turbine assembly is between 1.3 and 1.9. A gear assembly is configured to receive power from the interdigitated turbine assembly, and a fan assembly is configured to receive power from the gear assembly. The interdigitated turbine assembly and the gear assembly are together configured to allow the second turbine rotor to rotate at a second rotational speed greater than a first rotational speed at the first turbine rotor. The fan assembly and the gear assembly are together configured to allow the fan assembly to rotate at a third rotational speed less than the first rotational speed and the second rotational speed. The interdigitated turbine assembly, the gear assembly, and the fan assembly together have a maximum AN.sup.2 at the second turbine rotor between 30 and 90.

A turbine assembly including a first rotor assembly with a rotatable outer drum from which one or more stages of a plurality of outer drum airfoils is extended radially inward is provided. An outer casing surrounds the outer drum of the first rotor assembly. A seal assembly is coupled to the outer casing and positioned radially outward from an upstream-most stage of the plurality of outer drum airfoils. The seal assembly is positioned in axial alignment with the upstream-most stage of the plurality of outer drum airfoils. The seal assembly separates a first plenum from a second plenum. The second plenum is formed axially aft of the first plenum and is formed by the seal assembly, the outer casing, and the outer drum of the first rotor assembly. The first plenum is positioned radially outward from the upstream-most stage of the plurality of outer drum airfoils.

A turbine assembly including a first rotor assembly with a rotatable outer drum from which one or more stages of a plurality of outer drum airfoils is extended radially inward is provided. An outer casing surrounds the outer drum of the first rotor assembly. A seal assembly is coupled to the outer casing and positioned radially outward from an upstream-most stage of the plurality of outer drum airfoils. The seal assembly is positioned in axial alignment with the upstream-most stage of the plurality of outer drum airfoils. The seal assembly separates a first plenum from a second plenum. The second plenum is formed axially aft of the first plenum and is formed by the seal assembly, the outer casing, and the outer drum of the first rotor assembly. The first plenum is positioned radially outward from the upstream-most stage of the plurality of outer drum airfoils.

A counter-rotating turbine of an aircraft turbomachine, includes a casing including an endoscopy port configured for an endoscopy plug of a non-destructive testing device to pass into the casing. The endoscopy plug includes a mechanism for acquiring and transmitting images. The non-destructive testing device includes a mechanism for receiving and displaying images connected to the mechanism for acquiring and transmitting images by a wireless connection. First and second rotors are configured to rotate in opposite rotation directions, the second rotor having an endoscopy port in which the endoscopy plug is removably attached.

A counter-rotating turbine of an aircraft turbomachine, includes a casing including an endoscopy port configured for an endoscopy plug of a non-destructive testing device to pass into the casing. The endoscopy plug includes a mechanism for acquiring and transmitting images. The non-destructive testing device includes a mechanism for receiving and displaying images connected to the mechanism for acquiring and transmitting images by a wireless connection. First and second rotors are configured to rotate in opposite rotation directions, the second rotor having an endoscopy port in which the endoscopy plug is removably attached.

A turbine includes a first rotor and a second rotor that can rotate in opposite directions and are interleaved. The turbine further includes a ring to which abradable material is secured, the ring, unsegmented, extending between the first impellers of the first rotor and the second rotor, over a sector of between 350 and 360°, and, axially between an upstream end and a downstream end of the ring, the ring is held with the second rotor.

A gas turbine apparatus has a main shaft, a first plurality of blades mounted to the main shaft, a second plurality of blades each interposed between blades of the first plurality of blades, a barrel affixed to the second set of blades, a fuel line opening to an interior of the barrel, and an igniter cooperative with the interior of the barrel and adapted to selectively ignite fuel in the barrel. The first plurality of blades rotate in a direction opposite to a direction of rotation of the second plurality of blades. The fuel line passes a fuel into the interior of the barrel.