Upper attachment for trimmable horizontal stabiliser actuator

An upper attachment system for a trimmable horizontal stablizer actuator (THSA), the upper attachment comprising:

• a housing holding a yoke and a ballscrew;
• a nut coupled to the housing and cooperating with the ballscrew such that rotation of the ballscrew relative to the nut results in linear motion of the ballscrew;
• a recess formed between the yoke and the ballscrew and arranged to receive, in use, an upper part of a tie bar of the secondary load path of the actuator;
• and
• a biasing mechanism arranged such that, in use, when no axial load is applied to the tie bar, the yoke and the ballscrew are held by balanced forces from the biasing mechanism in a position within the recess, and such that when, in use, an axial load is applied to the yoke by the upper part of the tie bar, the balanced forces from the biasing mechanism are overcome and the axial load along with the biasing mechanism results in linear motion of the ballscrew in a first axial direction relative to the nut, wherein the linear motion moves the ballscrew toward the yoke and closes the recess around the upper part of the tie bar;
• comprising a no back system for preventing reverse rotation of the ballscrew relative to the nut, wherein the no back system is a friction disc arranged to provide a friction force resisting rotation of the nut.

An upper attachment system for a trimmable horizontal stablizer actuator (THSA), the upper attachment comprising:

• a housing holding a yoke and a ballscrew;
• a nut coupled to the housing and cooperating with the ballscrew such that rotation of the ballscrew relative to the nut results in linear motion of the ballscrew;
• a recess formed between the yoke and the ballscrew and arranged to receive, in use, an upper part of a tie bar of the secondary load path of the actuator;
• and
• a biasing mechanism arranged such that, in use, when no axial load is applied to the tie bar, the yoke and the ballscrew are held by balanced forces from the biasing mechanism in a position within the recess, and such that when, in use, an axial load is applied to the yoke by the upper part of the tie bar, the balanced forces from the biasing mechanism are overcome and the axial load along with the biasing mechanism results in linear motion of the ballscrew in a first axial direction relative to the nut, wherein the linear motion moves the ballscrew toward the yoke and closes the recess around the upper part of the tie bar;
• wherein the upper attachment further comprises a locking system to avoid inadvertent actuation of the system;
• and
• wherein the locking system includes a latch device mounted resiliently between the ballscrew and the housing, and wherein sufficient axial force on the ballscrew will overcome the resilience of the latch device and allow relative axial movement of the ballscrew and the housing.