stroke piston will cause tilt to be put on the tiltplate, and the A-end will cause the mount to trainright.Figure 12-7 is a simplified block diagramshowing the main element of the hydraulic powerdrive system under automatic control forclockwise and counterclockwise rotation.There are two principal problems in posi-tioning a gun to fire. One is to get an accurategun-order signal. This problem is solved by thedirector-computer combination. The otherproblem is to transmit the director signal promptlyto the gun so that the position and movementsof the gun will be synchronized with the signalsfrom the director.The problem of transforming gun-ordersignals to mount movements is solved by thepower drive and its control—the indicatorregulator. The indicator regulator controls thepower drive, and this, in turn, controls themovement of the gun.The indicator regulator receives an initialelectrical gun-order from the director-computer,compares it to the existing mount position, andsends an error signal to the hydraulic controlmechanism in the regulator. The hydraulic controlmechanism controls the flow to the stroke controlshaft, which positions the tilting box in the A-endof the transmission. Its tilt controls the volumeand direction of fluid pumped to the B-end and,therefore, the speed and direction of the driveshaft of the B-end. Through mechanical linkage,the B-end output shaft moves the gun in thedirection determined by the signal. At the sametime, B-end response is transmitted to theindicator regulator and continuously combineswith incoming gun-order signals to give theerror between the two. This error is modifiedhydraulically, according to the system ofmechanical linkages and valves in the regulator.When the gun is lagging behind the signal, itsmovement is accelerated; and when it begins tocatch up, its movement is slowed down so thatit will not overrun excessively.LANDING GEAR EMERGENCYSYSTEMIf the landing gear in a naval aircraft fails toextend to the down and locked position, theaircraft has an emergency method to extend thelanding gear. This text will cover the nitrogensystem.The nitrogen storage bottle system is aone-shot system powered by nitrogen pressurestored in four compressed nitrogen bottles(fig. 12-8). When the landing gear control handleis used to actuate the emergency landing gearsystem, a cable between the control and themanually operated nitrogen bottle opens theemergency gear down release valve on the bottle.Nitrogen from this bottle actuates the releasevalves on the other three bottles so that theydischarge. Nitrogen flows from the manuallyoperated bottle, actuates the dump valves, andcauses the shuttles within the shuttle valves on theFigure 12-7.—Operation of the hydraulic power drive.12-8
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