ports inside the MFC. These pressure ports direct thefuel flow to the vane actuators via tubing.This timing is accomplished by pumping the vanesto the full open position and maintaining 100 to 200 psigon the system. At the same time, be sure you check tosee if the bottom of the rig plates are parallel with eachother. NEVERrelax the pressure on the system whileperforming the rig plate check. If the pressure isrelaxed, the feedback lever may drift and the rig will beincorrect.When the system is full open, and 100 psig isapplied, try to move the bolt back and forth on theforward end of the cable at the bellcrank. If the boltcannot be moved, it most likely indicates a binding atthe front section of the cable assembly. Of course, this“assumes” that the bolt is of the correct diameter and isnormally free to move. If the bolt cannot be moved backand forth, reverse the pump selector handle to the RE(rod end) position. You then need to apply a few strokesto move the vanes slightly towards the closed position.If the bolt becomes free to move, the forward section ofthe cable assembly is definitely binding. Binding iseasily connected by loosening the jamnut on the forwardrod end bearing and rotating the rod end bearing a halfturn at a time. This adjustment shortens the distance(right-hand rotation) and usually solves the problem.Reinstall and recheck the rigging. If the rigging is stillslightly off, use the trimmer bracket adjustment to makethe correction.ThebottomlineWhat are you really trying to accomplish? Look atit this way. The system is pumped full open, and thepiston inside each actuator is physically bottomed out.This in turn fixes the position of the bellcrank bolt holewhen a minimum of 100 psig is maintained. If youmanually hold the feedback lever arm in order to matchthe bottom of the rig plates, the plates become parallelto each other. The two fixed ends now have a fixeddistance between them. By adjusting the length of thecable assembly, you will maintain a proper fit betweenthe two fixed points.You have now successfully accomplished a VSVfeedback cable rigging. You were able to do so by acombination of adjusting the fore and aft rod endbearings within the limitations and following thepublished trimmer bracket instructions.VSV SCHEDULINGVSV scheduling is verified by using the variablevane protractor (1C5714). You must check theprotractor for accuracy before every use on the engine.The check will detect any inaccuracies due to damage,wear, and so forth. Use the protractor setmaster(9441M67G01) to accomplish this test. The protractoris installed on the master vane located at the 9 o’clocksplit line, aft looking forward.CAUTIONDo not check the vane angle if idle speedis less than 4,900 rpm, or greater than 5,000rpm. Before adjusting the idle rpm screw onthe MFC, assure PLA mechanical andelectrical rigging is connect.Once the protractor’s accuracy has been verified,you are now ready to install the protractor on the engine.Install the protractor locator on the engine and ensure itmounts correctly (it will only goon one way correctly).If installed incorrectly, the shaft cannot be threadedon the vane stud. If the locator is wiggled around so thatthe shaft can be threaded on the vane stud, it will becocked, but the protractor can still be installed over thelocator. However, the vane angle is now 4° too far open.If the protractor is left in this position, the angle willbe 4° more open when checked at idle rpm than whencompared to the table.This means a perfectlyserviceable engine could be rejected because it failed theangle check. When installed correctly, the locator isflush to the lever and, at the same time, the shaft can bethreaded on the vane stud without wiggling it around.GAS TURBINE PRESERVATION ANDCORROSION CONTROLModern gas turbines and their support equipmentare dependent upon the structural soundness of themetals from which they are fabricated. The greatestthreat to the structural integrity of this equipment ismetal corrosion. With the higher demands being madeon these metals, both in strength and in closer tolerances,this equipment would rapidly deteriorate and becomeinoperativecontrol.without regular attention to corrosion2-33
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