Bell Helicopter Textron Inc. | Date: 2015-02-16
A flight control system having a control law, the control law operable to generate a modified pitch command, the modified pitch command representing a greater amount of collective pitch compared to an amount of collective pitch generated by a first pitch command, the modified pitch command being generated because a vertical descent speed of the rotorcraft at a given forward airspeed is greater than a threshold. A method of avoiding entry into an undesired vertical descent speed region during operation of a rotorcraft, including measuring a forward airspeed; evaluating a vertical descent of the rotorcraft; and generating a modified collective pitch command in respond to a first collective pitch command having a collective pitch value that would cause the rotorcraft to experience a vertical descent rate greater than a threshold value at the forward airspeed of the rotorcraft.
Bell Helicopter Textron Inc. | Date: 2015-05-19
A method for fabricating a repair laminate for a composite part having an exposed surface includes applying a bonding material to the exposed surface and forming an uncured ply stack assembly on the bonding material. The uncured ply stack assembly is formed by forming and compacting a series of uncured ply stacks. The ply stack assembly and bonding material are then cured.
Bell Helicopter Textron Inc. | Date: 2015-01-20
A vibration control system for a rotor hub provides vibration attenuation in an aircraft by reducing the magnitude of rotor induced vibratory. The system can include a force generating device attached to a rotor hub which rotates along with the rotor at the rotational speed of the rotor. Vibratory shear force is generated by rotating unbalanced weights each about an axis non-concentric with the rotor hub axis at high speed to create large centrifugal forces. The rotational speed of the weights can be a multiple of the rotor rotational speed to create shear forces for canceling rotor induced vibrations. The amplitude of the generated shear force is controlled by indexing the positions of the unbalanced weights relative to each other, while the phase of the shear force is adjusted by equally phasing each weight relative to the rotor.
Bell Helicopter Textron Inc. | Date: 2015-06-23
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.
Bell Helicopter Textron Inc. | Date: 2015-07-14
In some embodiments, a rotor system for a rotorcraft includes a yoke, a blade, and a grip that is configured to couple the blade to the yoke. The grip has a plurality of baseline layers and a compliant layer. The baseline layers each have a plurality of fibers disposed in a first polymeric matrix. The compliant layer has a plurality of fibers disposed in a second polymeric matrix. The compliant layer is stronger than the baseline layer and the first polymeric matrix has a different chemical composition than the second polymeric matrix.