to prevent excess air pressure loss but not enough to hinder  movement of the cable. Pressure seals should be inspected  at regular intervals to determine that the retaining rings are  in place. If a retaining ring comes off, it may slide along the  cable and cause jamming of a pulley.  [Figure 2-74] Control surfaces should move a certain distance in either  direction from the neutral position. These movements must  be synchronized with the movement of the flight deck  controls. The flight control system must be adjusted (rigged)  to obtain these requirements. The tools for measuring surface  travel primarily include protractors, rigging fixtures, contour  templates, and rulers. These tools are used when rigging  flight control systems to assure that the desired travel has  been obtained. Generally speaking, the rigging consists of  the following: Fairleads may be made from a nonmetallic material, such as  phenolic, or a metallic material, such as soft aluminum. The  fairlead completely encircles the cable where it passes through  holes in bulkheads or other metal parts. Fairleads are used to  guide cables in a straight line through or between structural  members of the aircraft. Fairleads should never deflect the  alignment of a cable more than 3° from a straight line. Pressure seals are installed where cables (or rods) move  through pressure bulkheads. The seal grips tightly enough  1.  Positioning the flight control system in neutral and  temporarily locking it there with rig pins or blocks; 2.  Adjusting system cable tension and maintaining  rudder, elevator, and ailerons in the neutral position;  and 3.  Adjusting the control stops to the aircraft manufacturer’s  specifications. Figure 2-73.  Pulley wear patterns.  Figure 2-74.  Cable guides. 2-44 Travel Adjustment Excessive cable tension Pully wear from misalignment Pully too large for cable Cable misalignment Frozen bearing Normal condition Guard pin Pulley Bracket Solid fairlead Rubstrip Split fairlead Fairlead Control cable Bulkhead groove Bulkhead Air seal Retaining rings Pressurized Unpressurized