to receive a pivot pin. The pivot pin passes through the lever and through two mounting holes in the stanchion. The bottom of the lower lever is fitted with a roller that bears on the stem screw on top of the valve sleeve. The vertical position of the roller on the lower lever determines the vertical distance that the valve sleeve may move. Thus, it controls the size of the initial opening of the control valve. The levers are mounted in such a way that, as the upper lever is withdrawn, the lever arm ratio of both levers is increased by an equal amount. When the upper lever is fully withdrawn, the ratio of each lever is 2:1, and the ratio through the lever system (upper and lower levers) is 4:1. In this case the initial control valve opening is minimum. A plunger movement of 1 inch, acting through the upper lever, would move the lower lever 1/2 inch; the lower lever, in turn, would move the valve sleeve and stem 1/4 inch downward. A critical point to consider is the position of the levers when the valve stem is seated by cam action at the termination of each arrestment stroke. The levers are so mounted and adjusted that the bearing surfaces of the levers are level when the valve is seated. When the bearing surfaces are level, the distance across the lever system is the same regardless of the ratio setting. Because of this, the point of closing of the valve is independent of the aircraft weight selector. It is a function of the cam only; therefore, it is constant. As the engine is retracted, the upper lever rises a distance equal to the movement of the plunger. If the ratio is 1:1, the valve sleeve rises the same distance. In this case the initial valve opening is maximum. If the ratio is 4:1, however, the valve sleeve rises only one-fourth the distance that the plunger moves. In this case the initial valve opening is minimum. The lever setting may be adjusted to any setting within the two extremes previously discussed; the particular setting used is dependent upon the weight of the aircraft to be arrested. The weight setting is made with the engine in battery position prior to landing the aircraft. Adjustment of the setting determines the position of the valve sleeve. Therefore, it also sets the amount the valve will open at the beginning of the arrestment stroke. Similarly, it determines the rate of closure during the stroke so that the valve will always seat at the same runout. The valve stem sleeve allows a relatively unloaded and cushioned opening at the beginning of the stroke. The lever system, if set for a heavy aircraft, reduces the allowable valve stem opening and thus increases the resistance of the valve to the flow of fluid. The energy of the aircraft is dissipated by forcing fluid through the restricted valve opening. Electrical System The electrical system provides, controls, and safeguards the distribution of electrical energy to the weight selector motor and the synchro indicators. The electrical circuits (fig. 3-5) are the control valve weight selector circuit and the indicator circuit. Control Valve Weight Selector Circuit Due to the varying weights and landing speeds of carrier-based aircraft, it is necessary to vary the initial opening of the CRO valve and have a smaller initial opening for heavier aircraft than for lighter aircraft. The variation of the setting of the CRO valve is the function of the aircraft weight selector motor unit. (See fig. 3-5.) Normally, the settings are made electrically by depressing an increase or decrease push button located at the control valve. The settings can also be accomplished manually by a handwheel at the control valve. The aircraft weight selector is motor operated from the 440-volt, 60-hertz, 3-phase ship’s power supply. A fused switch box or breaker is provided to energize or de-energize the control circuit. To increase and decrease settings, the direction of the aircraft weight selector motor rotation is controlled by the motor controller. Should an electrical failure occur, the settings can be made manually by pulling out on the handwheel and turning in either the increase or the decrease direction. Settings on the aircraft weight selector are monitored locally at the control valve motor unit dial and remotely by synchro receivers located at Pri-Fly and the deckedge control station. 3-8