Upper attachment for trimmable horizontal stabiliser actuator

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

• a housing that holds 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 a 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.