Question 226Motor Plants - 1st Asst/Chief

The correct answer is C) Valve D, when depressed, allows the retained pneumatic pressure within the shutdown servomotor to be relieved. This is correct because the pneumatic circuit shown is likely part of an engine shutdown or emergency control system. Valve D is likely a manual override valve that, when depressed, releases the pneumatic pressure in the shutdown servomotor, allowing the engine to be restarted or the system to be reset. The other answer choices are incorrect because they do not accurately describe the function of this specific pneumatic circuit. The circuit is not used for camshaft position adjustment (A), the piston labeled A is not providing a low-pressure signal (B), and the circuit is not designed to nullify an actuating signal due to diminished oil pressure (D).