You are cruising at Speed X, EAS for maximum range. When you climb and target maximum range, your speed should be:

• A. Faster than X
• B. Equal to X
• C. Slower than X
• D. Unchanged from X

Answer: (C)

Maximum range is achieved at the speed that gives the best lift-to-drag ratio (L/D max). When you climb, air density falls, which changes the drag balance and the speed at which L/D max occurs. To stay on the most efficient point in thinner air, you need to operate at a lower equivalent airspeed than your cruise value. In other words, the speed for maximum range should be reduced as you climb. Flying faster would increase drag drag relative to lift and reduce range; staying at the same speed wouldn’t place you at the optimal L/D max in the thinner air. So, you should fly slower than your cruise EAS to pursue maximum range while climbing.