The pneumatic circuit shown in the illustration is part of a complex large low speed engine control system. Which of the following statements describes the function of this circuit? Illustration MO-0117

Correct Answer: Option C — Valve D, when depressed, allows the retained pneumatic pressure within the shut-down servo motor to be relieved.

Manual depression of valve D vents retained pneumatic control air from the shut-down servo motor, allowing the engine to return to an operational status or resetting the safety shutdown circuit.