Question 4 UFIV01 - Chief Engineer - UFIV

The Correct Answer is C ### Explanation of Correct Option (C) Option C is correct because it describes the standard procedure for visually inspecting the upper cylinder liner bore through the scavenging-air ports in a two-stroke engine (the type typically used for main propulsion and often featuring scavenging ports, as implied by the inspection method). 1. **Positioning the Piston at BDC (Bottom Dead Center):** To inspect the upper liner bore, the piston must be moved down to BDC. When the piston is at BDC, the scavenging-air ports are fully uncovered, allowing visual access to the critical wear area of the liner (the upper portion where the rings primarily operate during combustion). 2. **Removing the Air Box Handhole Cover:** The scavenging-air ports are located in the cylinder liner wall and communicate with the surrounding air box (also known as the scavenging belt or receiver). To gain access to the ports for inspection, the handhole covers on the air box must be removed. 3. **Inspecting Through Scavenging-Air Ports:** This is the specific pathway used for visual inspection of the liner condition (e.g., scoring, pitting, wear step) without dismantling the cylinder head or pulling the piston. ### Explanation of Incorrect Options **A) With the particular piston positioned at BDC and the corresponding oil pan handhole cover removed, inspect the upper liner bore through the scavenging-air ports.** * **Incorrect Element:** Removing the **oil pan** handhole cover provides access to the crankcase, connecting rod, and piston skirt from below, but it does not provide access to the **scavenging-air ports**, which are located on the cylinder liner wall, separate from the crankcase. **B) With the particular piston positioned at TDC and the corresponding oil pan handhole cover removed, inspect the upper liner bore through the scavenging-air ports.** * **Incorrect Elements:** * **Piston Position:** When the piston is at **TDC (Top Dead Center)**, it covers the scavenging-air ports, making inspection impossible. The piston must be at BDC. * **Handhole Cover:** Access requires removal of the **air box** cover, not the oil pan cover. **D) With the particular piston positioned at TDC and the corresponding air box handhole cover removed, inspect the upper liner bore through the scavenging-air ports.** * **Incorrect Element:** The piston must be positioned at **BDC (Bottom Dead Center)** to fully expose the scavenging-air ports and the critical upper section of the liner for inspection. Positioning it at TDC blocks the ports.