Patent Description:
Various types and configurations of geartrains for an aircraft propulsion system are known in the art for an aircraft. While these known aircraft propulsion system geartrains have various benefits, there is still room in the art for improvement.

<CIT> relates to a turbine engine having an upstream propeller and an inner rotor driving rotation of an inlet shaft of a step-down gearbox, the gearbox includes an outlet shaft driving rotation of the rotor of the upstream propeller and an outlet shaft driving rotation of a downstream propeller.

According to an aspect of the invention, an assembly is provided for an aircraft as claimed in claim <NUM>.

According to another aspect of the invention, another assembly is provided for an aircraft as claimed in claim <NUM>.

Some embodiments of the invention are as claimed in the dependent claims thereof.

<FIG> schematically illustrates a propulsion system <NUM> for an aircraft. The aircraft may be an airplane, a helicopter, a drone (e.g., an unmanned aerial vehicle (UAV)), a spacecraft or any other manned or unmanned aerial vehicle. This aircraft may be configured as a vertical take-off and landing (VTOL) aircraft or a short take-off and vertical landing (STOVL) aircraft. The aircraft propulsion system <NUM> of <FIG>, for example, is configured to generate power for first direction propulsion (e.g., propulsive thrust) during a first mode of operation and to generate power for second direction propulsion (e.g., propulsive lift) during a second mode of operation, where the first direction is different than (e.g., angularly offset from) the second direction. The first mode may be a horizontal flight mode (e.g., a forward flight mode) where the first direction propulsion is substantially horizontal propulsive thrust; e.g., within five degrees (<NUM>°), ten degrees (<NUM>°), etc. of a horizontal axis. The second mode may be a vertical flight and/or hover mode where the second direction propulsion is substantially vertical propulsive lift; e.g., within five degrees (<NUM>°), ten degrees (<NUM>°), etc. of a vertical axis. The aircraft propulsion system <NUM>, of course, may also be configured to generate both the first direction propulsion (e.g., horizontal propulsion) and the second direction propulsion (e.g., vertical propulsion) during a third mode (e.g., a transition mode) of operation.

The aircraft propulsion system <NUM> of <FIG> includes one or more bladed propulsor rotors such as, for example, at least one bladed first propulsor rotor <NUM> and at least one bladed second propulsor rotor <NUM>. The aircraft propulsion system <NUM> of <FIG> also includes a gas turbine engine core <NUM> configured to rotatably drive the one or more propulsor rotors - the first propulsor rotor <NUM> and/or the second propulsor rotor <NUM>.

The first propulsor rotor <NUM> may be configured as a ducted rotor such as a fan rotor. The first propulsor rotor <NUM> of <FIG> is rotatable about a first rotor axis <NUM>. This first rotor axis <NUM> is an axial centerline of the first propulsor rotor <NUM> and may be horizontal when the aircraft is on ground and/or during level aircraft flight. The first propulsor rotor <NUM> includes at least a first rotor disk <NUM> and a plurality of first rotor blades <NUM> (one visible in <FIG>); e.g., fan blades. The first rotor blades <NUM> are distributed circumferentially around the first rotor disk <NUM> in an annular array. Each of the first rotor blades <NUM> is connected to and projects radially (relative to the first rotor axis <NUM>) out from the first rotor disk <NUM>.

The second propulsor rotor <NUM> may be configured as an open rotor such as a propeller rotor or a helicopter (e.g., main) rotor. Of course, in other embodiments, the second propulsor rotor <NUM> may alternatively be configured as a ducted rotor such as a fan rotor; e.g., see dashed line duct. The second propulsor rotor <NUM> of <FIG> is rotatable about a second rotor axis <NUM>. This second rotor axis <NUM> is an axial centerline of the second propulsor rotor <NUM> and may be vertical when the aircraft is on the ground and/or during level aircraft flight. The second rotor axis <NUM> is angularly offset from the first rotor axis <NUM> by an included angle <NUM>; e.g., an acute angle or a right angle. This included angle <NUM> may be between sixty degrees (<NUM>°) and ninety degrees (<NUM>°); however, the present disclosure is not limited to such an exemplary relationship. The second propulsor rotor <NUM> includes at least a second rotor disk <NUM> and a plurality of second rotor blades <NUM>; e.g., open rotor blades. The second rotor blades <NUM> are distributed circumferentially around the second rotor disk <NUM> in an annular array. Each of the second rotor blades <NUM> is connected to and projects radially (relative to the second rotor axis <NUM>) out from the second rotor disk <NUM>.

The engine core <NUM> extends axially along a core axis <NUM> between a forward, upstream airflow inlet <NUM> and an aft, downstream exhaust <NUM>. The core axis <NUM> may be an axial centerline of the engine core <NUM> and may be horizontal when the aircraft is on the ground and/or during level aircraft flight. This core axis <NUM> may be parallel (e.g., coaxial) with the first rotor axis <NUM> and, thus, angularly offset from the second rotor axis <NUM>. The engine core <NUM> of <FIG> includes a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. The turbine section <NUM> of <FIG> includes a high pressure turbine (HPT) section 48A and a low pressure turbine (LPT) section 48B (also sometimes referred to as a power turbine section).

The engine sections <NUM>-48B are arranged sequentially along the core axis <NUM> within an engine housing <NUM>. This engine housing <NUM> includes an inner case <NUM> (e.g., a core case) and an outer case <NUM> (e.g., a fan case). The inner case <NUM> may house one or more of the engine sections <NUM>-48B; e.g., the engine core <NUM>. The outer case <NUM> may house the first propulsor rotor <NUM>. The outer case <NUM> of <FIG> also axially overlaps and extends circumferentially about (e.g., completely around) the inner case <NUM> thereby at least partially forming a (e.g., annular) bypass flowpath <NUM> radially between the inner case <NUM> and the outer case <NUM>.

Each of the engine sections <NUM>, 48A and 48B includes a bladed rotor <NUM>-<NUM> within that respective engine section <NUM>, 48A, 48B. Each of these bladed rotors <NUM>-<NUM> includes a plurality of rotor blades arranged circumferentially around and connected to one or more respective rotor disks. The rotor blades, for example, may be formed integral with or mechanically fastened, welded, brazed, adhered and/or otherwise attached to the respective rotor disk(s).

The compressor rotor <NUM> is connected to the HPT rotor <NUM> through a high speed shaft <NUM>. At least (or only) these engine components <NUM>, <NUM> and <NUM> collectively form a high speed rotating structure <NUM>. This high speed rotating structure <NUM> is rotatable about the core axis <NUM>. The LPT rotor <NUM> is connected to a low speed shaft <NUM>. At least (or only) these engine components <NUM> and <NUM> collectively form a low speed rotating structure <NUM>. This low speed rotating structure <NUM> is rotatable about the core axis <NUM>. The low speed rotating structure <NUM> and, more particularly, its low speed shaft <NUM> may project axially through a bore of the high speed rotating structure <NUM> and its high speed shaft <NUM>.

The aircraft propulsion system <NUM> of <FIG> includes a powertrain <NUM> that couples the low speed rotating structure <NUM> to the first propulsor rotor <NUM> and that couples the low speed rotating structure <NUM> to the second propulsor rotor <NUM>. The powertrain <NUM> of <FIG> includes a geartrain <NUM>, a transmission <NUM> and a gearing <NUM>; e.g., bevel gearing. The powertrain <NUM> of <FIG> also includes one or more shafts <NUM>-<NUM> and/or other intermediate torque transmission devices for coupling the geartrain <NUM> to the second propulsor rotor <NUM>. The powertrain <NUM> may also include one or more intermediate torque transmission devices for coupling the geartrain <NUM> to the first propulsor rotor <NUM>.

An input to the geartrain <NUM> is coupled to the low speed rotating structure <NUM> and its low speed shaft <NUM>, where the low speed rotating structure <NUM> forms a power input for the geartrain <NUM>. A first output from the geartrain <NUM> is coupled to the first propulsor rotor <NUM>, where the first propulsor rotor <NUM> forms a first power output (e.g., load) for the geartrain <NUM>. A second output from the geartrain <NUM> is coupled to the second propulsor rotor <NUM> through the powertrain elements <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, where the second propulsor rotor <NUM> forms a second power output (e.g., load) for the geartrain <NUM>.

An output of the transmission <NUM> is connected to the gearing <NUM> through the transmission output shaft <NUM>. This transmission <NUM> may be configured to selectively couple (e.g., transfer mechanical power between) the geartrain output shaft <NUM> and the transmission output shaft <NUM>. During the first mode of operation, for example, the transmission <NUM> may be configured to decouple the geartrain output shaft <NUM> from the transmission output shaft <NUM>, thereby decoupling the low speed rotating structure <NUM> from the second propulsor rotor <NUM>. During the second mode of operation (and the third mode of operation), the transmission <NUM> may be configured to couple the geartrain output shaft <NUM> with the transmission output shaft <NUM>, thereby coupling the low speed rotating structure <NUM> with the second propulsor rotor <NUM>. The transmission <NUM> may be configured as a clutched or clutchless transmission.

An output of the gearing <NUM> is connected to the second propulsor rotor <NUM> through the second propulsor shaft <NUM>. This gearing <NUM> provides a coupling between the transmission output shaft <NUM> rotating about the axis <NUM>, <NUM> and the second propulsor shaft <NUM> rotating about the second rotor axis <NUM>. The gearing <NUM> may also provide a speed change mechanism between the transmission output shaft <NUM> and the second propulsor shaft <NUM>. The gearing <NUM>, however, may alternatively provide a <NUM>:<NUM> rotational coupling between the transmission output shaft <NUM> and the second propulsor shaft <NUM> such that these shafts <NUM> and <NUM> rotate at a common (e.g., the same) speed. Furthermore, in some embodiments, the gearing <NUM> and the transmission output shaft <NUM> may be omitted where the functionality of the gearing <NUM> is integrated into the transmission <NUM>. In still other embodiments, the transmission <NUM> may be omitted where decoupling of the second propulsor rotor <NUM> is not required and/or where an optional additional speed change between the second output of the geartrain <NUM> and the second propulsor rotor <NUM> is not required.

During operation of the aircraft propulsion system <NUM>, air enters the engine core <NUM> through the airflow inlet <NUM>. This air is directed into a (e.g., annular) core flowpath <NUM> which extends sequentially through the compressor section <NUM>, the combustor section <NUM>, the HPT section 48A and the LPT section 48B to the exhaust <NUM>. The air within this core flowpath <NUM> may be referred to as core air.

The core air is compressed by the compressor rotor <NUM> and directed into a (e.g., annular) combustion chamber <NUM> of a (e.g., annular) combustor <NUM> in the combustor section <NUM>. Fuel is injected into the combustion chamber <NUM> through one or more fuel injectors <NUM> (one visible in <FIG>) and mixed with the compressed core air to provide a fuel-air mixture. This fuel-air mixture is ignited and combustion products thereof flow through and sequentially cause the HPT rotor <NUM> and the LPT rotor <NUM> to rotate. The rotation of the HPT rotor <NUM> drives rotation of the high speed rotating structure <NUM> and its compressor rotor <NUM>. The rotation of the LPT rotor <NUM> drives rotation of the low speed rotating structure <NUM>. The rotation of the low speed rotating structure <NUM> drives rotation of the first propulsor rotor <NUM> through the geartrain <NUM> during a select mode or modes of operation; e.g., the first and the third modes of operation. The rotation of the low speed rotating structure <NUM> drives rotation of the second propulsor rotor <NUM> through the geartrain <NUM> during a select mode or modes of operation; e.g., the second and the third modes of operation. During the first mode of operation, the transmission <NUM> may decouple the low speed rotating structure <NUM> from the second propulsor rotor <NUM> such that the low speed rotating structure <NUM> does not drive rotation of the second propulsor rotor <NUM>. The second propulsor rotor <NUM> may thereby be stationary (or windmill) during the first mode of operation.

During the first and the third modes of operation, the rotation of the first propulsor rotor <NUM> propels bypass air (separate from the core air) through the aircraft propulsion system <NUM> and its bypass flowpath <NUM> to provide the first direction propulsion; e.g., the forward, horizontal thrust. During the second and the third modes of operation, the rotation of the second propulsor rotor <NUM> propels additional air (separate from the core air and the bypass air) to provide the second direction propulsion; e.g., vertical lift. The aircraft may thereby takeoff, land and/or otherwise hover during the second and the third modes of operation, and the aircraft may fly forward or otherwise move during the first and the third modes of operation.

Referring to <FIG>, the geartrain <NUM> may include multiple (e.g., epicyclic) interconnected gear systems <NUM> and <NUM>. Referring to <FIG> and <FIG>, the first gear system <NUM> includes a first sun gear <NUM>, a first ring gear <NUM>, a plurality of first intermediate gears <NUM> and a first carrier <NUM>. The first sun gear <NUM> is rotatable about a rotational axis <NUM> of the geartrain <NUM>, which rotational axis <NUM> may be parallel (e.g., coaxial) with the axis <NUM>, <NUM>. The first ring gear <NUM> circumscribes the first sun gear <NUM> and is rotatable about the axis <NUM>, <NUM>, <NUM>. Each of the first intermediate gears <NUM> is disposed between and meshed with the first sun gear <NUM> and the first ring gear <NUM>. Each of the first intermediate gears <NUM> is rotatably mounted to the first carrier <NUM>. The first carrier <NUM> is rotatable about the axis <NUM>, <NUM>, <NUM>.

Referring to <FIG> and <FIG>, the second gear system <NUM> includes a second sun gear <NUM>, a second ring gear <NUM>, a plurality of second intermediate gears <NUM> and a second carrier <NUM>. The second sun gear <NUM> is rotatable about the axis <NUM>, <NUM>, <NUM>. This second sun gear <NUM> is coupled to (e.g., via a shaft <NUM> and/or another coupling device) and rotatable with the first sun gear <NUM>. The second ring gear <NUM> circumscribes the second sun gear <NUM> and is rotatable about the axis <NUM>, <NUM>, <NUM>. This second ring gear <NUM> is coupled to (e.g., via a shaft <NUM> and/or another coupling device) and rotatable with the first carrier <NUM>. Each of the second intermediate gears <NUM> is disposed between and meshed with the second sun gear <NUM> and the second ring gear <NUM>. Each of the second intermediate gears <NUM> is rotatably mounted to the second carrier <NUM>. The second carrier <NUM> is rotatable about the axis <NUM>, <NUM>, <NUM>.

Referring to <FIG>, the first propulsor rotor <NUM> is coupled to and is configured to be rotatably driven by the first carrier <NUM>. The first propulsor rotor <NUM> of <FIG>, for example, is connected to the shaft <NUM> extending between and connected to the first carrier <NUM> and the second ring gear <NUM>. The first propulsor rotor <NUM> may thereby be coupled to the geartrain <NUM> (e.g., and positioned) between the first gear system <NUM> and the second gear system <NUM>. The second propulsor rotor <NUM> (see also <FIG>) is coupled to and is configured to be rotatably driven by the second sun gear <NUM> and, thus, the first sun gear <NUM>. The low speed rotating structure <NUM> and its LPT rotor <NUM> are coupled to and are configured to rotatably drive the first ring gear <NUM>. With this arrangement, the first gear system <NUM> is between and couples the low speed rotating structure <NUM> and the first propulsor rotor <NUM>. The geartrain <NUM> along with its first and its second gear systems <NUM> and <NUM> are between and couple the low speed rotating structure <NUM> and the second propulsor rotor <NUM> (see also <FIG>). The low speed rotating structure <NUM> and its LPT rotor <NUM> may thereby power / drive rotation of the first propulsor rotor <NUM> and/or the second propulsor rotor <NUM> (see also <FIG>) through the geartrain <NUM> and its interconnected gear systems <NUM> and <NUM>. Including the multiple gear systems <NUM> and <NUM> within a common gearbox may facilitate torque sharing between the first gear system <NUM> and the second gear system <NUM>. This torque sharing may facilitate a reduction in sizing of the first gear system <NUM> and/or the second gear system <NUM>, compared to a gearbox with a single gear system.

The aircraft propulsion system <NUM> may include one or more brakes 120A and 120B (generally referred to as "<NUM>") and/or one or more lock devices 122A and 122B (generally referred to as "<NUM>"). The first brake 120A and/or the first lock device 122A may be located at a first location 124A, or another suitable location. The second brake 120B and/or the second lock device 122B may be located at a second location 124B, or another suitable location.

The first brake 120A of <FIG> is configured to brake (e.g., slow and/or stop) rotation of the second carrier <NUM> about the axis <NUM>, <NUM>, <NUM>. The first lock device 122A is configured to lock (e.g., fix, prevent) rotation of the second carrier <NUM> about the axis <NUM>, <NUM>, <NUM>, for example, following the braking of the second carrier <NUM> to a zero rotational speed about the axis <NUM>, <NUM>, <NUM> using the first brake 120A. When the second carrier <NUM> is rotationally fixed (e.g., during the second mode of operation of <FIG>), a rotational speed of the first propulsor rotor <NUM> may decrease (compared to when the second carrier <NUM> is free to rotate).

Reducing the rotational speed of the first propulsor rotor <NUM> during, for example, the second mode of operation reduces or substantially eliminates (e.g., de minimis) the first direction propulsive thrust generated by the first propulsor rotor <NUM>. Reducing first propulsor rotor thrust may, in turn, increase power available for driving rotation of the second propulsor rotor <NUM> and/or facilitate substantial second direction aircraft movement; e.g., without first direction aircraft movement. However, maintaining some rotation of the first propulsor rotor <NUM> may maintain lubrication of one or more bearings (e.g., bearings <NUM> in <FIG>) supporting the first propulsor rotor <NUM> and/or prevent bearing related damage. For example, when a component supported by a bearing is not rotating, shock loads may damage one of more internal components of the bearing. Examples of such bearing damage may include, but are not limited to, brinelling and false brinelling. Maintaining some rotation of the first propulsor rotor <NUM> of <FIG> may also or alternatively prevent an exhaust backflow through the bypass flowpath <NUM> into the inlet <NUM>. Maintaining some rotation of the first propulsor rotor <NUM> may still also or alternatively prevent debris (e.g., sand, dirt, dust, etc.) from entering the inlet <NUM> during the second mode of operation where the aircraft is more likely to be near the ground; e.g., for landing or takeoff.

The second brake 120B of <FIG> is configured to brake (e.g., slow and/or stop) rotation of the second propulsor rotor <NUM> about the axis <NUM> (see <FIG>) and, thus, the sun gears <NUM> and <NUM>. The second lock device 122B is configured to lock (e.g., fix, prevent) rotation of the second propulsor rotor <NUM> about the axis <NUM> (see <FIG>) (and rotation of the sun gears <NUM> and <NUM> about the axis <NUM>, <NUM>, <NUM>), for example, following the braking of the second propulsor rotor <NUM> to a zero rotational speed about the axis <NUM> using the second brake 120B. When the second propulsor rotor <NUM> of <FIG> is rotationally fixed (e.g., during the first mode of operation of <FIG>), the geartrain <NUM> may transfer (e.g., all, minus losses in the powertrain <NUM>) the power output from the low speed rotating structure <NUM> and its LPT rotor <NUM> to the first propulsor rotor <NUM> and any powertrain element(s) therebetween (when included).

To enter the third mode of operation from the first mode of operation, the second lock device 122B may be disengaged and/or the second brake 120B may be released. The second propulsor rotor <NUM> may thereby begin to rotate along with the already rotating first propulsor rotor <NUM>. Similarly, to enter the third mode of operation from the second mode of operation, the first lock device 122A may be disengaged and/or the first brake 120A may be released. The first propulsor rotor <NUM> may thereby begin to rotate faster along with the already rotating second propulsor rotor <NUM>. When both of the propulsor rotors <NUM> and <NUM> are rotating / free to rotate (e.g., during the third mode of operation of <FIG>), the geartrain <NUM> may transfer (e.g., all, minus losses in the powertrain <NUM>) the power output from the low speed rotating structure <NUM> and its LPT rotor <NUM> to (I) the first propulsor rotor <NUM> and the powertrain element(s) therebetween and (II) the second propulsor rotor <NUM> and the powertrain element(s) therebetween.

Referring to <FIG>, the first brake 120A and/or the second brake 120B may each be configured as or otherwise include a disk brake <NUM>. The disk brake <NUM> of <FIG> includes a brake rotor <NUM> and one or more brake pads <NUM>. The brake rotor <NUM> is configured rotatable with the respective propulsor rotor <NUM>, <NUM>. The brake rotor <NUM>, for example, may be connected to and rotatable with the respective shaft <NUM>, <NUM>, or another rotating element (directly or indirectly) rotatable with the respective propulsor rotor <NUM>, <NUM>. The brake pads <NUM> are anchored to a stationary structure <NUM>, which may be part of the engine housing <NUM> and/or an airframe of the aircraft (see <FIG>). The brake pads <NUM> may be actuated by one or more brake actuators <NUM> (e.g., hydraulic brake actuators) to move the brake pads <NUM> from an open position to a closed position. In the open position, the brake pads <NUM> are spaced from and do not engage (e.g., contact) the brake rotor <NUM> (see position of <FIG>). In the closed position, the brake pads <NUM> engage (e.g., contact) and clamp onto (e.g., squeeze) the brake rotor <NUM>. Frictional rubbing between the brake pads <NUM> and the brake rotor <NUM> is operable to brake rotation of the brake rotor <NUM> and, thus, the respective shaft <NUM>, <NUM> (or another rotating element) connected thereto. The first and the second brakes <NUM> of the present disclosure, however, are not limited to such an exemplary disk brake configuration. Furthermore, it is contemplated the first and/or the second brake <NUM> may alternatively be configured as another type of brake such as, for example, a drum brake or a set of clutch plates.

Referring to <FIG>, the first lock device 122A and/or the second lock device 122B may each be configured as a splined lock device <NUM>; e.g., a splined coupling. The lock device <NUM> of <FIG>, for example, includes an inner lock element <NUM> (e.g., a splined shaft), an outer lock element <NUM> (e.g., a splined sleeve) and an actuator <NUM>. The inner lock element <NUM> is rotatable about the axis <NUM>, <NUM>, <NUM>. The outer lock element <NUM> is rotationally fixed about the axis <NUM>, <NUM>, <NUM>. However, the actuator <NUM> is configured to move (e.g., axially translate) the outer lock element <NUM> along the axis <NUM>, <NUM>, <NUM> and the inner lock element <NUM> between an unlocked position (see dashed line in <FIG>) and a locked position (see solid line in <FIG>; see also <FIG>). At the unlocked position, inner splines <NUM> of the outer lock element <NUM> are disengaged (e.g., spaced) from outer splines <NUM> of the inner lock element <NUM>. At the locked position, the inner splines <NUM> of the outer lock element <NUM> are engaged (e.g., meshed) with the outer splines <NUM> of the inner lock element <NUM> (see also <FIG>). With this arrangement, when the lock device <NUM> is unlocked and its outer lock element <NUM> is in the unlocked position, the inner lock element <NUM> may rotate (e.g., freely, unencumbered by the outer lock element <NUM>) about the axis <NUM>, <NUM>, <NUM>. However, when the lock device <NUM> is locked and its outer lock element <NUM> is in the locked position of <FIG>, the outer lock element <NUM> is meshed with the inner lock element <NUM> and prevents rotation of the inner lock element <NUM> about the axis <NUM>, <NUM>, <NUM>.

Referring to <FIG> and <FIG>, the inner lock element <NUM> of the first lock device 122A may be configured as part of or may be attached (directly or indirectly) to the shaft <NUM>, or any other element rotatable therewith. The inner lock element <NUM> of the second lock device 122B may be configured as part of or may be attached (directly or indirectly) to the geartrain output shaft <NUM>, or any other element rotatable therewith. While the inner lock element <NUM> of <FIG> and <FIG> is described as the rotating element and the outer lock element <NUM> is described as the rotationally fixed element, the operation of these elements may be switched in other embodiments. In particular, the inner lock element <NUM> may alternatively be configured as the rotationally fixed element and axially translatable by the actuator <NUM>, and the outer lock element <NUM> may be configured as the rotating element. Furthermore, various other types of rotational lock devices are known in the art, and the present disclosure is not limited to any particular ones thereof.

In some embodiments, referring to <FIG>, the geartrain <NUM> and its gear systems <NUM> and <NUM> may be arranged within a nacelle <NUM> for the aircraft propulsion system <NUM>. This nacelle <NUM> may be configured discrete from an airframe of the aircraft. The aircraft propulsion system <NUM> and its nacelle <NUM>, for example, may be mounted to a component of the airframe (e.g., a fuselage, a wing, etc.) by a pylon. In other embodiments, referring to <FIG>, the second gear system <NUM> may be arranged remote from the engine core <NUM> and the front gear system <NUM>. The first propulsor rotor <NUM>, the engine core <NUM> and the first gear system <NUM> of <FIG>, for example, may be arranged in the nacelle <NUM>. The second gear system <NUM> of <FIG>, by contrast, may be arranged in or otherwise with a component <NUM> of the aircraft airframe; e.g., a fuselage, a wing, etc. Of course, in still other embodiments, at least the engine core <NUM> and geartrain <NUM> including its first and second gear systems <NUM> and <NUM> may be arranged within the aircraft airframe.

In some embodiments, referring to <FIG>, the low speed rotating structure <NUM> may be configured without a compressor rotor. In other embodiments, referring to <FIG>, the low speed rotating structure <NUM> may include a low pressure compressor (LPC) rotor <NUM>' arranged within a low pressure compressor (LPC) section 46A of the compressor section <NUM>. In such embodiments, the compressor rotor <NUM> may be a high pressure compressor (HPC) rotor within a high pressure compressor (HPC) section 46B of the compressor section <NUM>.

The engine core <NUM> (e.g., see <FIG>) may have various configurations other than those described above. The engine core <NUM>, for example, may be configured with a single spool, with two spools (e.g., see <FIG>), or with more than two spools. The engine core <NUM> may be configured with one or more axial flow compressor sections, one or more radial flow compressor sections, one or more axial flow turbine sections and/or one or more radial flow turbine sections. The engine core <NUM> may be configured with any type or configuration of annular, tubular (e.g., CAN), axial flow and/or reverser flow combustor. The present disclosure therefore is not limited to any particular types or configurations of gas turbine engine cores. Furthermore, it is contemplated the engine core <NUM> of the present disclosure may drive more than the two propulsor rotors <NUM> and <NUM>, or a single one of the propulsor rotors <NUM> and <NUM> and/or one or more other mechanical loads; e.g., electric machines, electric generators, electric motors, etc. The aircraft propulsion system <NUM>, for example, may include two or more of the first propulsor rotors <NUM> and/or two or more of the second propulsor rotors <NUM>. For example, the aircraft propulsion system <NUM> of <FIG> includes multiple second propulsor rotors <NUM> rotatably driven by the low speed rotating structure <NUM>. These second propulsor rotors <NUM> may rotate about a common axis. Alternatively, each second propulsor rotor <NUM> may rotate about a discrete axis where, for example, the second propulsor rotors <NUM> are laterally spaced from one another and coupled to the low speed rotating structure <NUM> through a power splitting geartrain <NUM>.

Claim 1:
An assembly for an aircraft, comprising:
a geartrain (<NUM>) including a first gear system (<NUM>) and a second gear system (<NUM>);
the first gear system (<NUM>) including a first sun gear (<NUM>), a first ring gear (<NUM>), a plurality of first intermediate gears (<NUM>) and a first carrier (<NUM>), the first ring gear (<NUM>) rotatable about an axis (<NUM>, <NUM>, <NUM>), the plurality of first intermediate gears (<NUM>) between and meshed with the first sun gear (<NUM>) and the first ring gear (<NUM>), each of the plurality of first intermediate gears (<NUM>) rotatably mounted to the first carrier (<NUM>), and the first carrier (<NUM>) rotatable about the axis (<NUM>, <NUM>, <NUM>);
the second gear system (<NUM>) including a second sun gear (<NUM>), a second ring gear (<NUM>), a plurality of second intermediate gears (<NUM>) and a second carrier (<NUM>), the plurality of second intermediate gears (<NUM>) between and meshed with the second sun gear (<NUM>) and the second ring gear (<NUM>), and each of the plurality of second intermediate gears (<NUM>) rotatably mounted to the second carrier (<NUM>);
a first propulsor rotor (<NUM>) coupled to the first carrier (<NUM>); and
a rotating structure (<NUM>) coupled to the first ring gear (<NUM>) and comprising a turbine rotor (<NUM>), the rotating structure (<NUM>) configured to drive rotation of the first propulsor rotor (<NUM>) through the geartrain (<NUM>), characterised in that
the second ring gear (<NUM>) is rotatable about the axis (<NUM>, <NUM>, <NUM>) and coupled to the first carrier (<NUM>).