🔍 Key Concepts

• Fixed-pitch vs controllable-pitch propellers and how direction (ahead/astern) is obtained • Difference between reversing and non-reversing diesel engines • Typical use of slow-speed vs medium-speed diesels on large ships with reduction gears

💭 Think About

• If the reduction gear is nonreversing and the propeller is fixed-pitch, where must the ability to go astern come from? • On large oceangoing ships, which speed class of diesel (slow-speed or medium-speed) is more commonly used with reduction gears instead of direct drive? • Match the needed engine feature (reversing or non-reversing) with the propeller type (fixed-pitch) and the gear type (nonreversing).

✅ Before You Answer

• Be certain how a fixed-pitch propeller changes direction of thrust (what must change to go from ahead to astern?). • Confirm which engine type is typically direct-coupled without reduction gears on large ships (slow-speed vs medium-speed). • Verify that your choice has an engine type whose reversing/non-reversing capability logically matches a nonreversing gear and fixed-pitch propeller.