We’re comparing two different climb speeds — Page 214, Lesson 253

This is the tail end of a question set on climb performance, and I want to make sure you understand what these four options are actually describing, because they’re testing a very specific distinction. We’re comparing two different climb speeds. Option (i) is the speed for the best rate of climb, and option (iii) is the speed for the best angle of climb. Those are two different speeds, and they give you two different results. The best rate of climb gives you the greatest gain in altitude per unit of time — that’s your fastest way to get high, and it’s what you use for normal en-route climbs. The best angle of climb gives you the greatest gain in altitude per unit of horizontal distance — that’s your steepest climb path, and it’s what you use to clear an obstacle. Now, the question is asking what happens if you use a slightly reduced speed compared to each of those optimum speeds. If you fly slightly slower than the best rate-of-climb speed, you get a slightly reduced rate of climb. You’re still climbing, but you’re not gaining altitude as quickly per unit of time. If you fly slightly slower than the best angle-of-climb speed, you get a slightly reduced angle of climb. You’re still climbing, but your flight path is not as steep — you’re not gaining as much altitude per unit of horizontal distance. So the pattern is: a small speed reduction below the best rate speed costs you rate, and a small speed reduction below the best angle speed costs you angle. That’s the relationship the options are testing. Now, the second part of the excerpt, item (d), is a separate question, and it’s asking you to match four statements to the correct climb condition. The four statements are: a good rate of climb, the best rate of climb, a good angle of climb, and the best angle of climb. The key distinction here is between “good” and “best.” A good rate of climb is a rate that is acceptable but not the maximum — it’s a climb rate you might get at a speed that isn’t the optimum. The best rate of climb is the maximum rate, achieved only at the specific best-rate speed. Similarly, a good angle of climb is a climb angle that is acceptable but not the steepest, while the best angle of climb is the steepest, achieved only at the specific best-angle speed. So when you’re matching those four statements, you need to think about which speed gives you the best value and which speed gives you merely a good value. The best values come only at the optimum speeds; the good values come at speeds that are close but not exact. That’s the substance of this excerpt — it’s the distinction between rate and angle, and between best and good, and how a small speed reduction affects each one.