Basics, Climbing

Chapter 7.1

Climb Speeds

Two climb speeds are defined when climbing with an airplane: the first is the highest angle of climb and the second is the highest gain in height over time.

Dependence of Vx and Vy on Flight Altitude

The change of Vx and Vy depending on the flight altitude

The graph below shows the variations in airspeed with respect to altitude:

In most AFMS, the increase in Vx, or the decrease in Vy, respectively, when the flight altitude is increased is not published.

As a general rule:

Vx increases by about 1/2 kt for each 1000 ft gain in altitude

Vy decreases by about 1 kt for each 1000 ft gain in altitude

Constant Climb Speed vs Constant Climb Rate

A climb flight with a basic school airplane is carried out at full power and at constant airspeed. There is no possibility of increasing the power with the increase in altitude.

The rate of climb decreases with altitude because of the decrease in power.

Influence of the wind during the climb

These three climbs take place over the same time period with the same indicated airspeed. The rate of climb remains unchanged. However the ground distance changes with the wind.

Questions

What is Vx and when do you fly that speed?

• The airspeed for the best angle of climb
• After take-off, to pass over a possible obstacle

What is Vy and when do you fly that speed?

• The airspeed for the best climb rate
• When the maximum height must be reached in a minimum amount of time

How does the rate of climb of the aircraft vary with an increase in altitude?

• It decreases

At what Indicated Airspeed must you fly, when you would like to climb with Vy and there is a strong headwind?

• The same Indicated Airspeed as when there is no wind