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D. Starter shutoff valve
(Ref. Fig. 004)
(1) Closing operation The starter shutoff valve remains closed with the solenoid de-energized. Inlet air pressure is routed through a downstream facing probe and regulator orifice to chamber "A". This pressure is routed through the de-energized solenoid (position shown) and into chamber "B". Since the pressures on both sides of diaphragm "B" are equal, no net force remains. The pressure in chamber "A" exerts a force on diaphragm "A"; this force, in combination with the closing torsion spring force, closes the starter control valve.
(2) Opening operation The starter shutoff valve is opened by energizing either of the solenoid coils. Energizing the solenoid actuates the solenoid ball to the position opposite that shown. The chamber "A" pressure is then blocked at the solenoid and the chamber "B" pressure is vented to ambient through the open rating orifice. With chamber "B" vented, the chamber "A" pressure is sensed on both diaphragms "A" and "B". Since diaphragm "B" is larger than diaphragm "A" the valve will actuate to the butterfly open position when the valve inlet pressure is sufficient to overcome the closing torsion spring. The starter shutoff valve opening rate is controlled by the rate at which chamber "B" vents to ambient. These rates are controlled by the regulator orifice and the open rating orifice, respectively.
(3) Manual override operation The starter shutoff valve is manually opened by first pushing the wrench button and then rotating the lever. Pushing the wrench button vents chamber "A" and "B" past the manual override vent ball. Since the manual override vent is large compared the regulator orifice, the chamber "A" and "B" pressure decreases to ambient pressure and thus there is no diaphragm force in the actuator. The handle can be rotated against the closing torsion spring to open the butterfly. The manual override lever is constructed so that the wrench button is automatically retained in the pressed position as long as the lever is manually rotated to the valve-open position. When the handle is released, the torsion spring turns the shaft to the butterfly closed position and the button is automatically returned to the closed position by the action of the vent ball spring and the valve returns to normal operation.
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Starter Shutoff Valve - Schematic Cross Section
Figure 004
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D. Starter shutoff valve
(Ref. Fig. 004A)
(1) Closing operation The starter air valve remains closed with the solenoid de-energized. Inlet air pressure is routed through a downstream facing probe and an opening rate orifice in a chamber solenoid closed by non-return valve (position shown). The pressure in opening chambers is vented to ambient through the solenoid ball and the closing-rate orifice. The pressure in chambers at opposite position of the opening chambers is vented to ambient through the vent orifices. The internal springs of the pneumatic actuators in combination with the closing torsion spring force, closes the starter control valve.
(2) Opening operation The starter air valve is opened by energizing either of the solenoid coils. Energizing the solenoid actuates the solenoid ball to the position opposite that shown and open the non-return valve. Inlet air pressure is routed in the opening chambers, then is sensed on both diaphragms and pistons of the pneumatic actuators. The pressure increase in the opening chambers and actuate the pistons when the pressure is sufficient to overcome the internal springs and the closing torsion spring. The pistons actuate to the butterfly open position. The starter air valve opening rate is controlled by the rate at which chambers at opposite position of the opening chambers vents to ambient. These rates are controlled by the open rating orifice, the purging orifice and the closing rate orifice.
(3) Manual override operation The starter air valve is manually opened by rotating the lever because there is no diaphragm force and pressure in the pneumatic actuators. The handle can be rotated against the closing torsion spring to open the butterfly. When the handle is released, the torsion spring turns the shaft to the butterfly closed position and the valve returns to normal operation. 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：A320飛機維護手冊 AMM 起動 STARTING(7)
