🔍 Key Concepts

• Engine operating envelope shown by the shaded region and boundary lines • Difference between preferred continuous operating area (A) and limited/intermittent area (B) on a load diagram • Relationship between engine speed (% n), brake mean effective pressure (bmep), and load indicator (%)

💭 Think About

• Look at how areas A and B are positioned relative to the 100% MCR point and the % engine power lines. Which area appears to be the normal continuous rating? • Ask yourself: is the diagram suggesting that all shaded regions are equally desirable, or that some ranges are only allowed for short periods? • Consider what operating an engine for a long time at high bmep and relatively low rpm does to temperature and stress. Which labeled area corresponds to that condition?

✅ Before You Answer

• Identify which region on the diagram is closest to manufacturer-recommended continuous service (normal) operation. • Check whether the arrow drawn through area B suggests wide variation in speed at roughly constant bmep and what that implies for long‑term operation. • Verify that any statement allowing operation "until maintenance requirements become apparent" conflicts with the preventive maintenance and rating limits implied by the diagram.