What was found
(CAN) DURING A ROUTINE COCKPIT UNDER FLOOR INSPECTION, IT WAS FOUND THERE WAS EXCESSIVE WEAR ON THE LEFT POWER BRAKE VALVE TORQUE TUBE. THE WEAR WAS DIFFICULT TO DETECT AS IT WAS HIDDEN BY A PHENOLIC GUIDE BLOCK HOLDING THE LOWER PORTION OF THE TUBE STEADY. THE WEAR AFFECTS 50 PERCENT OF THE CIRCUMFERENCE AND 80 PERCENT OF THE TUBE THICKNESS. FAILURE OF THE PART COULD CAUSE A SERIOUS BRAKE PROBLEM.