Making the grade

After that, achieving the highest climb rate affords more options should an engine anomaly occur; altitude is life, after all. Best angle and best rate airspeeds, though, can make engines run hot. So, when the aircraft has sufficient altitude to handle emergencies, the pilot can lower the nose to a cruise climb airspeed that provides better engine cooling and forward visibility while maintaining a reasonable climb rate.

In “Engine Out: Optimizing Performance in a Glide” (November 2025 AOPA Pilot), I explored optimal gliding airspeeds and shared their interesting properties. We’ll do the same here for optimal climbing airspeeds.

The sidebar figures explain how the best angle of climb airspeed V_X and the best rate of climb airspeed V_Y are defined and determined in flight tests. Best angle of climb V_X occurs at the airspeed that maximizes excess thrust. (See Figures 1 and 2, below.) Best rate of climb V_Y is found at the airspeed that maximizes excess power. (See Figure 3, below.) During certification, test pilots fly the aircraft at maximum power and record the vertical speed across a wide range of airspeeds to produce the curve in Figure 4, from which both V_X and V_Y can be determined.

These curves betray interesting properties about optimal climbing airspeeds. V_Y divides the front and back side of the power curve. While some define airspeeds below the maximum endurance airspeed as the back side of the power curve, using V_Y as the boundary instead has added benefits. At airspeeds faster than V_Y, pulling back on the yoke causes the airplane to ascend and pushing forward makes the aircraft descend. Most flight is spent in cruise flight, so correcting altitude deviations with the yoke is intuitive. But flying below V_Y means these controls act backward in that pulling back on the yoke makes the aircraft descend and pushing forward results in a climb (see “Are We There Yet?” March 2022 AOPA Pilot). The effects of power, however, are constant throughout the airspeed spectrum.

Optimizing engine care and forward visibility

The shape of the curve in Figure 4 (below) shows that climb rate isn’t terribly sensitive to small deviations from V_Y. In my own Beechcraft Bonanza, I convert from the 96-knot best rate airspeed to a cruise climb at 120 knots. In most situations, the climb rate is still acceptable. It’s worth noting, however, that POH climb performance typically assumes adhering to V_Y so if making a climb gradient is critical in a departure procedure, ensure that your airplane can still offer acceptable performance at a higher climb speed.

Wind effects

V_Y is not affected by air movement during a climb, but the published V_X almost never achieves the best angle of climb when winds are at play (see Figure 4). When flying into a headwind or upwardly moving air, a pilot can enjoy the increased climb angle and improve it further by flying a bit slower. With a tailwind or downdraft, however, climb angle suffers and the optimal airspeed is slightly faster.