4. LESSON 23 - SLOW FLIGHT AND STALLS

Key points:

  • If the stick will not raise the nose, ease it forward
  • If the stick will not lift a wing, ease it forward
  • Recognizing and preventing a stall is better than having to deal with one
  • Before deliberately stalling, be sure that pilot and glider are prepared

During the following exercises you will experience what happens when the glider’s wing stalls. You will learn to recognize the symptoms of an approaching stall, so that you can take action to avoid stalling, and recover promptly from an inadvertent stall.

THEORY SUMMARY

Chapter 2 – Basic Aerodynamics, gave a fuller description of the theory for stalling. A pilot can stall the glider by trying to get the wing to do more than it is capable of.
The wing’s capability is determined by:

  • original shape – as manufactured
  • changed shape – by bugs or rain
  • speed – controlled by the pilot
  • angle of attack – controlled by the pilot.

A pilot’s demands on the wing often consist of little more than carrying the weight of the glider plus crew. These demands can be increased by: 

  • winch launching
  • steep turns
  • pulling up from a dive 
  • most aerobatics
  • increased weight/ballast

Do note that stalling is caused by something the pilot does to the glider, typically when distracted.
Once a stall happens, an instinctive reaction to a nose drop is to move the stick back further, or to a wing drop to try using the stick (ailerons) to pick it up. This lesson is all about helping you to understand the consequences of distraction and to change your instinctive response, should you stall the glider.

If you move the stick back and the glider does not respond by pitching up, or you move it sideways and the glider does not respond, ease the stick forwards.

THREE EXERCISES – THE PREPARATION

Before you undertake exercises that involve large changes in speed and altitude, you will have to perform the pre-manoeuvre/aerobatic checklist (see Lesson 4.3). To save valuable flying time, you can prepare for the checklist before flight, but you will have to actually perform it just before the exercise. In addition, we advise you to trim the glider for a normal speed and to not perform exercises in the direction of the sun – the bright light would limit your vision.

1 STALL AND RECOVERY

You will start this exercise by flying clearing turns; normal turns left then right (or vice versa) that allow you to look all around and vertically downwards to make sure that no other aircraft are near or beneath you. After these turns, your instructor will show you the symptoms of the approaching stall with the wings level, while you follow through on the controls.

If the nose is raised even a little above the normal attitude (1), the glider’s airspeed will reduce, and the noise of the airflow will change, becoming quieter. The effects of the ailerons may change, and the glider may buffet. In spite of the instructor’s attempts to hold up the nose with the elevator, it will drop (2). To recover from the stall, the stick is eased forward to regain normal flying speed (3), and is then used to return the glider to the normal gliding attitude.

If you move the stick back and the glider does not respond by pitching up, ease the stick forwards.

2 MUSHING STALL

Your instructor will have already shown you what to do if the stick will not raise the nose. This is the same if the nose has dropped or not. The second case we call a mushing stall.
Recognition is the same; recovery is the same. If you move the stick back and the glider does not respond by pitching up, ease the stick forwards. 

3 RECOVERING FROM A WING DROP

Your instructor will now show you what to do if the ailerons do not pick up a wing (perhaps better described as not rolling the glider). Recognition is the same; recovery is the same.

If you move the stick sideways and the glider does not respond, ease the stick forwards.

We don’t like telling you what not to do, but it’s worth emphasising in this case that you shouldn’t try to use either ailerons or rudder to pick up a wing.

It is important that you are able to recognize and react to the warning signs of an impending stall, so that you will always recover quickly. Your instructor will ask you to practice stalls and recoveries very often, perhaps every flight. This is to ensure that recognition of an approaching stall becomes second nature, and you will instinctively recover quickly if this ever happens unexpectedly in your later flying career.

MUCH MORE IMPORTANT: STALL PREVENTION

If you do allow yourself to get distracted, particularly when stressed, you can unthinkingly apply the control inputs that stall the glider. Always pay close attention to the airspeed when flying and react to the warning signs of an impending stall at any stage by moving the stick forward.