Question 37 3AE01 - Third Assistant Engineer

The Correct Answer is B **Explanation for Option B (Compressed air):** Compressed air starting systems often utilize vane-type fluid motors (also known as air motors or rotary vane motors) to convert the pneumatic energy (high-pressure air) into mechanical rotation. * **Vane Motor Mechanism:** In a vane-type fluid motor, the compressed air pushes against retractable vanes mounted eccentrically within a rotor housed inside a cylinder. This pressure differential causes the rotor to spin rapidly. * **Application:** This spinning motion is then transmitted via a gear train (often including a Bendix drive or similar mechanism) to engage and turn the flywheel, thereby starting the internal combustion engine. Vane motors are preferred in many heavy-duty, industrial, or marine compressed air starting systems due to their high power-to-weight ratio and immediate torque. **Explanation for Incorrect Options:** **A) Jet flow:** "Jet flow" (or sometimes "air-jet") is not a common nomenclature for a primary engine starting system mechanism. If it refers generally to the flow of air, it describes the medium, not the type of motor mechanism used to convert the energy (which is the vane motor). **C) Electric:** Electric starting systems use electric motors (DC motors), which convert electrical energy into mechanical rotation using magnetic fields and commutation (e.g., permanent magnet motors or series-wound motors). They do not use vane-type fluid motors. **D) Centrifugal:** Centrifugal force is a principle sometimes used within the engagement mechanism (like a centrifugal clutch or Bendix drive) of an engine starter motor (whether electric or pneumatic), but it does not describe the primary motor that converts the input energy into rotational motion.