Aircraft Brake Tube Adjuster Mechanism

In modern multi-disc aircraft brakes, the Tube Adjuster is a key component of the automatic wear adjustment system, ensuring consistent brake performance as the brake discs and linings wear over time.

Function Overview:

During brake operation, as the pistons push the pressure plate to squeeze the brake discs, a small amount of material wears off the friction surfaces.
To maintain a constant clearance between the piston and the discs, the Tube Adjuster automatically compensates for this wear.

Main Components:

1. Tube Adjuster:
   A threaded or ratcheting sleeve that moves incrementally to reset the piston’s “rest” position after each braking cycle.
2. Housing:
   Encloses and supports the adjuster assembly, ensuring alignment with the piston and torque tube.
3. Follower / Pawl Mechanism:
   Engages with the adjuster when piston movement exceeds a preset limit, allowing a controlled step adjustment.
4. Return Spring:
   Returns the adjuster and follower to their initial position when hydraulic pressure is released.

Working Principle:

1. Brake Application:
   Hydraulic pressure moves the piston forward, applying the brake discs.
   When wear occurs, the piston travels slightly farther than normal.
2. Adjustment:
   If this extra travel exceeds a specific distance, the adjuster mechanism engages, advancing the tube adjuster to take up the slack caused by wear.
3. Brake Release:
   When hydraulic pressure is removed, the return spring restores the assembly to its normal position — now with a corrected piston-to-disc clearance.

Importance:

The Tube Adjuster ensures:

• Consistent brake pedal feel and efficiency
• Automatic compensation for lining and disc wear
• Reduced maintenance frequency and increased safety