Actual Aircraft Maintenance Practices

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Next we could adjust Rudder Control Cables RA and RB. First, we should make sure that the R4 (Fig.505and 502) rig pin can be easily installed in the feel, centering and trim mechanism and adjust the turnbuckles for cables RA and RB at the same time to 270 +-18 pounds. Make sure that rig pin R3 (Fig.503) can be easily installed in the left forward quadrant. Then, ensure that none of the cable seals bend the cables and adjust the cables if it is necessary. Then remove the rig pins R3 and R4. Next, cycle the rudder pedals through their full travel 25 times and check that the cables are not bent by the fairleads, rub strips, or grommets that are in the system. Make sure that the cable guards are installed correctly and that the pulleys turn freely, the cables are installed through the necessary grommets and air pressure seals. Then, the cable should be lubricated for full travel over their pulleys, grommets, fair leads, and quadrants. After finished these steps, we could Install rig pin R4 and adjust the cable tension to the load shown in (Fig. 502) and confirm that rig pin R3 can be easily installed. Then remove the rig pins and move the pedals through one full travel cycle and do a check of the cable tension. If the cable tension loading is correct, we could install clip locks on all the turnbuckles and ask the qualified person to check the safety.

After we finished the adjustment of the control cables, we could adjust the Rudder Power Control Actuator (PCA) now. This procedure will make sure that the rudder trailing edge does not move (use a tolerance of 0.10 inch (2.54 mm) left or right of the rudder neutral position) when only one PCA is powered at a time. First, we should turn the rudder trim switch counterclockwise until the trim position indicator shows 3 to 5 units of left trim. This is because due to the large tolerance of rig pin hole R4, trim is input into the system during initial adjustment to ensure a good repeatable position of the rudder trailing at the neutral position.

Then, manually turn the feel, centering and trim aft quadrant clockwise against the spring force until rig pin R4 can be installed. This will make a stable position for the PCA adjustment procedure because the mechanism springs hold the rig pin hole to positively ground the ratio-changer mechanism. Next step is disconnected the bottom end of the YELLOW (right) control rod from the yaw damper summing lever and install rig pin R5 in the middle PCA input crank. Then, use a bungee cord to put a load on the top PCA torque tube assembly in a clockwise direction, to remove the backlash in the top PCA linkage. Next, adjust the BLACK (left) control rod between the yaw damper summing lever and the bottom PCA. Make sure that rig pin R8 fits loosely in the load limiter/cam at the yaw damper linkage and this step is to remove removes the backlash from the middle and bottom PCA linkages. Then, Remove rig pin R8 but do not tighten the lock nuts because the lock nuts will be tightened after the control rod is adjusted in the Yaw Damper Summing Lever adjustment procedure. Then supply pressure to the left hydraulic system only and make sure that all the person and equipments were clear from the area to prevent injury or damage. Now, the middle PCA was powered and this step is for the middle PCA adjustment only.

To adjust the PCA, first step is loosen the lock nut to let you adjust the PCA rod and this will let you move the rudder left or right of neutral a small distance. If increase the length of the PCA input rod to move the rudder left of neutral a small distance and turn the input rod in the clockwise direction to move the rudder to the right and counterclockwise to move it to the left. Then stop for three minutes or move the top and bottom PCA input rods across the neutral position, to bleed the unwanted pressure from the center and right hydraulic systems. This will make the rudder position become stable. Make sure that the Rudder position is very near neutral and the Rudder trailing edge is not out of the groove in the rudder index plate (Fig. 502). Then, tighten the lock nuts and the input rod bolts and make sure that the Rudder does not move from its neutral position when the lock nuts are tightened and make sure that the Rudder does not move from the datum position when the top and bottom PCAs are adjusted.

Then we could remove the power from the left hydraulic system and supply pressure to the center hydraulic system only for the adjustment of the Top Rudder PCA. After top PCA was powered, we could use the middle PCA adjustment procedure to adjust the top PCA but do not disconnect and move the other PCA input rods once the PCA has been adjusted, stop for three minutes to bleed the unwanted hydraulic pressure. Then repeat the procedure above to adjust the bottom Rudder PCA.

If a large adjustment is necessary to move the rudder to a position that an input rod end must be turned one - half turn at a time to move the rudder trailing edge very near neutral and the hydraulic system must be powered after each turn to do a check of the rudder position. First step is switch the tail flight control shutoff valve to OFF, then disconnect the PCA input rod end and turn it one-half turn at a time until the rudder is very near neutral and check the rudder position after connect the input rod and the tail flight control shutoff valve was ON. When the rudder is very near neutral, connect and tighten the PCA input rod end bolt and carry out small adjustment. Remember that do not disconnect all 3 of the Rudder PCA input rods with the hydraulic power was on because the Rudder will move quickly to its full left position and it is very dangerous.

After adjust the single Rudder PCA, we could adjust the Three Rudder PCAs System. First, only supply one hydraulic power each time to the relative Rudder PCA to check the rudder is in its neutral position as the datum and keep a record. Then, make sure that position was same of the three PCA. If not, do the above step again to carry out the small adjustment. Then, lockwire the lock nuts on the middle, top and bottom PCA input rods and connect the bottom end of the YELLOW control rod to the yaw damper summing lever. If it is necessary, adjust the rod until the bolt can be easily installed and tighten the lock nut. Next, remove rig pins R4, R5 and the bungee cord and inspection on all the control rods. Make sure that control rod threads can be seen in at least one-half of the control rod inspection hole.

Then, we could do the adjustment procedure for the Rudder Ratio Changer Mechanism. First, disconnect the bottom end of the BLUE (left) control rod nearest the trim actuator from the feel, centering, and trim mechanism and supply pressure to the left, center, and right hydraulic systems and clear the working area. Then, install rig pin