• Opening the airbrakes leads to an increase in rate of descent (a steeper glide angle)
  
• Maintain the correct airspeed with the stick and control the glide path with the airbrakes
  
• Once you’ve unlocked the airbrakes, keep holding the lever

In this exercise you will learn about the effect of the airbrakes. Gliders have a long range; a glide ratio of 40:1 is not uncommon: a range of about 40 times your height. If you arrived at your airfield at 300 feet and didn’t use your airbrakes, you wouldn’t be on the ground until 2 or more miles later - assuming no headwind (and no obstacles). Few airfields are that long. Thanks to the airbrakes, we can land exactly where we want to.

USING THE AIRBRAKES

The airbrake lever is coloured blue in every glider. When you pull the lever, they open. The further you open them, the more air resistance (drag) they provide. If you push the lever all the way forward, you can feel and hear the lever going through a lock; after that they will remain closed. In many training gliders, the airbrake lever is combined with the wheel brake, and if you pull the lever all the way back you also operate the wheel brake.

It is important to keep holding the lever when you operate the airbrakes. If you let go, they often will not remain in the desired position, and they might even get sucked open completely. In the air, you should only let go when the lever is in the locked position.

You will start this lesson by trimming for a normal landing airspeed. After setting the trimmer, you will not need it again during this exercise. Open the airbrakes with your left hand. You will see a change in pitch and  an increase in your rate of sink. Close the airbrakes and repeat the first exercise, but now try to maintain the desired airspeed using the elevator. You will find that when you open the airbrakes you have to keep the nose a little further down, below the horizon (a lower pitch attitude). If you reduce the amount of airbrakes, you will need to adopt a slightly higher pitch attitude to continue flying at the desired airspeed. Finally, try to operate the airbrakes over their entire range, from closed to fully opened and back again, while using the stick to maintain a constant airspeed. The airbrakes create variable amounts of additional drag. They make it possible to land exactly where you want to land.

Lesson 4.24 has a warning on the use of airbrakes at higher airspeeds.