4. LESSON 25 – SPIRAL DIVES AND SPINS
- You need to be able to recognise and deal with spiral dives and spins without difficulty; frequent practice can help maintain these skills
- Prevention is best
- Before deliberately flying these manoeuvres be sure that pilot and glider are prepared
In this lesson, we will practice spiral dives and spins. This serves several purposes:
- You will learn to recognize their symptoms quickly
- With practice, recovery can become second nature, enabling your return to a normal flight condition at an early stage, with minimal altitude loss
- Most importantly, practice will help prevent these from happening to you.
Human feelings can be very important. This lesson could be the first time you encounter extreme attitudes, speeds or g-forces and if you are feeling apprehensive that’s perfectly understandable. If encountered by mistake these manoeuvres can be alarming, which can result in a sudden sensation of fear, which is so strong as to dominate or prevent reason and logical thinking. The manoeuvres in this exercise might, at first, feel uncomfor- table and disorienting. With knowledge, training and practice, however, we can master those human responses, leaving you able to follow the simple advice below. Once trained and practiced, you will probably even find these manoeuvres enjoyable – many pilots do.
Dealing with spiral dives and spins is straightforward, but the glider loses height, perhaps rapidly, while the pilot does so.It is VITAL that training is done only when there is enough height to spare: included with other preparations in the pre-manoeuvre checks detailed in Lesson 4.3.
When there is not enough height to spare pilots should do everything they can to avoid inadvertent manoeuvres.
A spiral dive is a situation that a glidercan get into without any help from the pilot, sometimes surprisingly quickly. It can get there, for example, if the nose is allowed to drop when banking for a turn, or if spin recovery is not fully completed.
Spiral Dive Recognition
A spiral dive is a very steep turn with a high and increasing airspeed:
- Indicated on ASI
- Airflow noise
- Increasing g-force
- Heavy, but effective flight controls
- BUT back-pressure on the stick will fly the glider further into thespiral dive
- a slower rotation than a spin
Spiral Dive Recovery
- Roll wings level with coordinated stick and rudder
- Ease out of the dive
If concerned about high speed, pulling back a little harder with wings level is better for the glider’s structure than using the airbrakes.
Spiral Dive Prevention
Maintain the attitude you want, in balance. If you do allow yourself to get distracted, you can unthinkingly allow a spiral dive to develop.
A spin can develop if you make the glider roll or yaw while stalled. The roll and yaw then reinforce each other rotating and descending vertically. The rate at which each of these occurs can vary between gliders and between different centre of gravity positions (pilot weights or dedicated spin ballast provision).
Each manufacturer selects a balance between difficult entry, enhancing safety for day-to-day flying, and easier ones which help demonstration and practice. Similarly, spin recovery actions can vary a little. The BGA teaches a standard spin recovery technique as a proven method of recovering from a spin. Each glider flight manual will detail a spin recovery technique, which in some cases may vary from the standard spin recovery and therefore must be memorised.
When the nose is alarmingly low, a natural, involuntary human reaction can be to hold the stick hard back, holding the glider into the spin. Training and practice at the standard spin recovery can overcome this.
A spin can be recognized as a disorienting combination of roll, yaw and pitch:
- Low airspeed
- Modest g-force
- Stick will not raise either the nose or the wing
Unless the flight manual says otherwise:
- Full opposite rudder (this can be heavy)
- Centralise ailerons
- Ease stick centrally forward until rotation stops (gently, make sure you move the stick far enough forward)
- As soon as rotation stops: centralise the rudder
- Ease out of dive (gently!)
Maintain the speed you want, in coordinated flight. Manage the workload. If you do allow yourself to get distracted, particularly when stressed, you can unthinkingly apply the control inputs that will spin the glider.
The main differences between a spin and a spiral dive are that in a spin the g-forces are not high and the ailerons are ineffective, whereas in a spiral dive the g-forces are high and the flight controls are heavy and effective. With plenty of practice the recovery methods described above will come to feel normal over time. Should you ever accidentally get into any of these situations you will need less time to ‘think’ and will gain time to act fast. But most likely recognizing the symptoms early will prevent you from accidentally ending up in a spin or spiral dive in the first place.