Abstract: A vibratory motion reduction system for a pylon assembly includes an inner member having an opening extending therein that receives a first end of the pylon assembly, an outer member moveably attached to the inner member, a tuning mass attached to the inner member and the outer member such that a vibratory motion of the pylon assembly accelerates the tuning mass, a spring member that couples to a second end of the pylon assembly, and the spring member and the tuning mass reduce the vibratory motion of the pylon assembly.

Abstract: A driveshaft misalignment measurement system for a drivetrain of an aircraft includes a driveshaft having a first end forming a driveshaft spline and a drivetrain subsystem including a spline adapted to connect to the driveshaft spline to form a splined connection. Rotational energy is transferred between the drivetrain subsystem and the driveshaft via the splined connection. The driveshaft misalignment measurement system also includes accelerometers coupled to the drivetrain configured to detect acceleration data and a flight control computer configured to measure misalignment at the splined connection using the acceleration data.

Abstract: A driveshaft misalignment measurement system for a drivetrain of an aircraft includes a driveshaft having a first end forming a driveshaft spline and a drivetrain subsystem including a spline adapted to connect to the driveshaft spline to form a splined connection. Rotational energy is transferred between the drivetrain subsystem and the driveshaft via the splined connection. The driveshaft misalignment measurement system also includes accelerometers coupled to the drivetrain configured to detect acceleration data and a flight control computer configured to measure misalignment at the splined connection using the acceleration data.

Abstract: A vibratory motion reduction system for a pylon assembly includes an inner member having an opening extending therein that receives a first end of the pylon assembly, an outer member moveably attached to the inner member, a tuning mass attached to the inner member and the outer member such that a vibratory motion of the pylon assembly accelerates the tuning mass, a spring member that couples to a second end of the pylon assembly, and the spring member and the tuning mass reduce the vibratory motion of the pylon assembly.

Abstract: An engine mount assembly for coupling an engine to an airframe includes a torsion bar, a lateral movement control assembly and a vertical movement control assembly. The torsion bar has a torsional stiffness and is coupled between the engine and the airframe such that torsional movement of the engine causes torsion in the torsion bar. The lateral movement control assembly has a lateral stiffness and is coupled between the torsion bar and the airframe such that lateral movement of the engine causes rotation of the torsion bar which reacts on lateral movement control assembly. The vertical movement control assembly has a vertical stiffness and is coupled between the engine and the airframe such that vertical movement of the engine reacts on the vertical movement control assembly. The engine mount assembly, thereby enables torsional, lateral and vertical movement of the engine to be independently controlled.

Abstract: A propulsion system for a tiltrotor aircraft includes an engine supported by the airframe and a fixed gearbox operably coupled to the engine. Inboard and outboard pedestals are supported by the airframe and positioned above the wing. A pylon assembly is rotatably coupled between the inboard and outboard pedestals. The pylon assembly includes a spindle gearbox having an input gear, a mast operably coupled to the input gear and a proprotor assembly operable to rotate with the mast. The spindle gearbox is rotatable about a conversion axis to selectively operate the tiltrotor aircraft between helicopter and airplane modes. A common shaft, rotatable about the conversion axis, is configured to transfer torque from an output gear of the fixed gearbox to the input gear of the spindle gearbox. Each of the inboard and outboard pedestals includes a journal bearing that provides a stiff coupling with the pylon assembly.

Abstract: According to one embodiment, an empennage attachment system features an aft attachment mechanism and a forward attachment system. The aft attachment mechanism is configured to be coupled to a tail section of a body of an aircraft and to an empennage proximate to an aft spar of the empennage. The aft attachment mechanism defines a pitch axis such that the aft attachment mechanism allows the empennage to rotate about the pitch axis. The forward attachment system is configured to be coupled to the tail section of the body and to the empennage proximate to a forward spar of the empennage. The forward attachment system is configured to restrict rotation of the empennage about the pitch axis to an allowable range of motion.

Abstract: A propulsion system for a tiltrotor aircraft includes an engine supported by the airframe and a fixed gearbox operably coupled to the engine. Inboard and outboard pedestals are supported by the airframe and positioned above the wing. A pylon assembly is rotatably coupled between the inboard and outboard pedestals. The pylon assembly includes a spindle gearbox having an input gear, a mast operably coupled to the input gear and a proprotor assembly operable to rotate with the mast. The spindle gearbox is rotatable about a conversion axis to selectively operate the tiltrotor aircraft between helicopter and airplane modes. A common shaft, rotatable about the conversion axis, is configured to transfer torque from an output gear of the fixed gearbox to the input gear of the spindle gearbox. Each of the inboard and outboard pedestals includes a journal bearing that provides a stiff coupling with the pylon assembly.

Abstract: A propulsion system for a tiltrotor aircraft includes an engine supported by the airframe and a fixed gearbox operably coupled to the engine. Inboard and outboard pedestals are supported by the airframe and positioned above the wing. A pylon assembly is rotatably coupled between the inboard and outboard pedestals. The pylon assembly includes a spindle gearbox having an input gear, a mast operably coupled to the input gear and a proprotor assembly operable to rotate with the mast. The spindle gearbox is rotatable about a conversion axis to selectively operate the tiltrotor aircraft between helicopter and airplane modes. A common shaft, rotatable about the conversion axis, is configured to transfer torque from an output gear of the fixed gearbox to the input gear of the spindle gearbox. Each of the inboard and outboard pedestals includes a journal bearing that provides a stiff coupling with the pylon assembly.

Abstract: A propulsion system for a tiltrotor aircraft includes an engine supported by the airframe and a fixed gearbox operably coupled to the engine. Inboard and outboard pedestals are supported by the airframe and positioned above the wing. A pylon assembly is rotatably coupled between the inboard and outboard pedestals. The pylon assembly includes a spindle gearbox having an input gear, a mast operably coupled to the input gear and a proprotor assembly operable to rotate with the mast. The spindle gearbox is rotatable about a conversion axis to selectively operate the tiltrotor aircraft between helicopter and airplane modes. A common shaft, rotatable about the conversion axis, is configured to transfer torque from an output gear of the fixed gearbox to the input gear of the spindle gearbox. Each of the inboard and outboard pedestals includes a journal bearing that provides a stiff coupling with the pylon assembly.

Abstract: An engine mount assembly for coupling an engine to an airframe includes a torsion bar, a lateral movement control assembly and a vertical movement control assembly. The torsion bar has a torsional stiffness and is coupled between the engine and the airframe such that torsional movement of the engine causes torsion in the torsion bar. The lateral movement control assembly has a lateral stiffness and is coupled between the torsion bar and the airframe such that lateral movement of the engine causes rotation of the torsion bar which reacts on lateral movement control assembly. The vertical movement control assembly has a vertical stiffness and is coupled between the engine and the airframe such that vertical movement of the engine reacts on the vertical movement control assembly. The engine mount assembly, thereby enables torsional, lateral and vertical movement of the engine to be independently controlled.

Abstract: According to one embodiment, an empennage attachment system features an aft attachment mechanism and a forward attachment system. The aft attachment mechanism is configured to be coupled to a tail section of a body of an aircraft and to an empennage proximate to an aft spar of the empennage. The aft attachment mechanism defines a pitch axis such that the aft attachment mechanism allows the empennage to rotate about the pitch axis. The forward attachment system is configured to be coupled to the tail section of the body and to the empennage proximate to a forward spar of the empennage. The forward attachment system is configured to restrict rotation of the empennage about the pitch axis to an allowable range of motion.