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AUTOMATIC BLADE FOLDING SYSTEM MAINTENANCE
CHAPTER 11 AIRCRAFT WHEELS, TIRES, AND TUBES

Aviation Structural Mechanic (H&S) 3&2 - How airplanes are built and how to maintain them
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cyclic pitch stick in neutral. Visually examine the control lock cylinder to make sure that the pin is aligned with its hole. When the controls are positioned, trip the FOLD manual override on the blade fold control valve and hold it in this position. No action should result. Release the override. Position the SAFETY VALVE switch to OPEN. Check that the SAFETY VALVE OPEN light comes on. Trip the manual override again. The dampers will position, the control lockpin will engage, and the blade lockpin will disengage. The blade will fold, and the PRI SERVO PRESS light will go off. WARNING Ensure that the path of the blade is clear before tripping the manual override. Failure to do so could result in personal injury or damaged to the aircraft. The cyclic control stick may have to be moved slightly around neutral to engage the control lockpin. Check the lights on the blade fold panel. CONT LOCKPIN ADV, BLADE FOLDED, CHECK BLADE FOLD, SAFETY VALVE OPEN, AND ACCESS DR ON lights should be lighted. The BLADE SPREAD light should be off. Trip the manual override button to SPREAD. The blade will spread and the lockpin will engage. The control lockpin will disengage.    The BLADE SPREAD and CHECK BLADE FOLD lights will come on. Position the SAFETY VALVE switch to CLOSED. Check to see that the SAFETY VALVE OPEN and CHECK BLADE FOLD lights go off within 1 1/2 seconds and that the FLIGHT POS light comes on. Release the rotor brake to make sure that the ROTOR BRAKE ON light goes off. Manually reposition the No. 1 blade to the right of the helicopter centerline. Position the safety valve switch to OPEN and the master switch to ON. Make sure that SAFETY VALVE OPEN and FOLD PWR ON lights come on. Check to see that the ACCESSORY DR ON light is on. The rotor brake should disengage automatically. Hydraulic pressure should disengage the blade positioner drive unit from the rotor brake disc. The final movements of blade positioning may result in a position hunting motion or chatter. If this chatter is sustained for more than 3 seconds, investi- gate the cause. Position the blade fold switch to FOLD. The No. 1 BLADE POSITION light will come on. Apply the rotor brake manually. Damper- positioners will position, the control lockpin will engage, and the CONT LOCKPIN ADV light will illuminate. The blade lockpin will retract, and the BLADE SPREAD light will go off. The BLADE FOLDED and CHECK BLADE FOLD lights will come on. NOTE: Automatic fold cycle time is approximatey 30 seconds for the rotary-wing positioning. The normal time for damper positioning is 5 seconds, and normal time for blade folding is 27 to 41 seconds. Make sure that the accumulator gauge on the No. 1 blade sleeve spindle maintains 3,000 psi. The damper-positioners should remain in full extended or autorotative position. The blades should remain folded. Position the blade fold switch to SPREAD, and check the reversing of operation. When the BLADE SPREAD light comes on, position the safety valve switch to CLOSED (SAFETY VALVE OPEN and FOLD PWR ON lights should then go out). Position MASTER and BLADE FOLD switches to OFF. CHECK BLADE FOLD light will go off, and FLIGHT POS light will come on. Visually check control lockpin for disengagement. Move the No. 1 blade to the left of the helicopter centerline. Repeat the automatic folding sequence. Following the hydraulic testing, inspect all components for external leakage. 10-20







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