Airplane manufacturers have done a lot of work carefully testing their planes to find out how they perform. It is important to become familiar with their findings to improve safety and performance. Vx and Vy are very important speeds to understand.
Vx – Best Angle
The best angle of climb (Vx) is the airspeed at which the aircraft will gain the most altitude per unit of distance flown. This means that a plane flown at Vx will make a steeper climb than at any other speed.
Vy – Best Rate
The best rate of climb (Vy) is the speed at which the aircraft will gain the most altitude per unit of time. This means that a plane flown at Vy will make a faster climb than at any other speed.
When are these used?
These speeds are most useful during takeoff. If you need to clear an obstacle, use Vx. If you are just trying to reach a higher altitude during most normal takeoffs climb at Vy.
If you are flying any distance it is usually preferable to climb at Vy until you are above pattern altitude. Then you can let the nose down and climb at a higher speed. This is often called a cruise climb. Refer to the POH to get an idea of a good cruise climb speed.
Using a cruise climb has several advantages. It gives you better visibility over the nose of the plane. The higher airspeed also allows you to cover more ground quicker and provides more airflow to cool the engine.