jpanside Posted February 12, 2014 Posted February 12, 2014 This is a follow up question regarding this thread: http://helicopterforum.verticalreference.com/topic/15012-cyclic-trim/ iChris explained beautifully what the MD 500 One Way Lock does, but I am left wondering...how?! http://download.mdhelicopters.com/etm/500/tech_manuals/md500pdf/500pubs/com/67/671010/pp1001.pdf What does the reservoir do? And, how does this system mechanically make it easier on the cyclic? My guess is that force applied to one end (not sure which end) of the lock exerts even greater force on the other end. Thus, a small force (cyclic) can be turned into a much larger force. If someone can explain this whole system, it would be a real treat, but I am thinking that MD does not want us to know. Would like to know more about how it works mechanically and about how it counters blowback and other helicopter behaviors. Thank you! 1 Quote
iChris Posted February 13, 2014 Posted February 13, 2014 This is a follow up question regarding this thread: http://helicopterforum.verticalreference.com/topic/15012-cyclic-trim/ iChris explained beautifully what the MD 500 One Way Lock does, but I am left wondering...how?! http://download.mdhelicopters.com/etm/500/tech_manuals/md500pdf/500pubs/com/67/671010/pp1001.pdf What does the reservoir do? And, how does this system mechanically make it easier on the cyclic? My guess is that force applied to one end (not sure which end) of the lock exerts even greater force on the other end. Thus, a small force (cyclic) can be turned into a much larger force. If someone can explain this whole system, it would be a real treat, but I am thinking that MD does not want us to know. Would like to know more about how it works mechanically and about how it counters blowback and other helicopter behaviors. Thank you! The one-way lock assembly is a self-contained hydraulic unit connected in series with the longitudinal control system. The one-way lock assembly functions as a control rod during longitudinal movement of the cyclic control stick. The piston of the assembly connects to the longitudinal idler bellcrank on the control support bracket and the input shaft connects to the cyclic interconnection torque tube. It mounts in the aircraft at an angle. The one-way lock assembly consists of a piston, a shaft, a spring loaded ball check valve, and a spring-loaded relief sleeve. The piston is inside a housing assembly serves as a hydraulic chamber supplied by the reservoir. The one-way lock prevents aft rotor system feedback forces from moving the cyclic control stick aft. Any tendency to pull the piston aft by a force acting on the lower rod end bearing will be resisted by a hydraulic lock formed by the ball check valve and hydraulic fluid trapped in the aft chamber. During forward control inputs, the piston acts as a simple control rod. Fluid is displaced around the ball check valve as pressure differentials warrant. When the pilot applies an aft cyclic control input to the forward rod end bearing and shaft, the shoulder of the shaft will travel aft to the limit of free play set by the nut before any pressure is exerted on the shaft. This travel of the shaft allows its plunger to unseat the ball check as long as aft control input is maintained. When control input is removed, a force still remains (feedback in an aft direction from the main rotor head), which will cause the ball check valve to reseat itself and "lock out" this unwanted feedback force. Rotor head forces up to 200 ±25 pounds that exert an aft motion to the cyclic control stick are hydraulically locked out of the control A relief mechanism built into the one-way lock assembly relieves the lock at forces above the design limit. If the one-way lock has a push rod shaft or check valve seizure in the closed valve position, a pull of to 10 to 20 pounds will be necessary to open the hydraulic relief valve and bypass the check valve. This additional pull will be required for each subsequent longitudinal movement of the cyclic stick. Temporary forces as high as 40 pounds may be experienced when flying in turbulence. This is outlined in the 500’s emergency procedures. (CLICK PHOTO TO ENLARGE) 1 Quote
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