Pilot safety and SIV training course – David Eyraud

MEMO

Asymmetric Stalls

 

There are 3 different exercises. Click on the link to go directly to the chosen exercise:
 
 
 
 
 

 

A – Cravat Removal

Practice performing asymmetric stalls to remove cravats.

Slow down symmetrically by at least 30 cm (after the contact point) and wait to stabilize the pendulum movements.

For a right asymmetric stall:

Weight shift to the left.
Look at your right wingtip.
Right arm: raise your elbow above your hand (to gain strength).
Bring down your right hand sharply! Quickly and completely: arm extended under your buttocks while watching the wing.
During this time: maintain counter (weight shift and brake) on the left to avoid turning.

At the moment of the asymmetric stall:

  • the wing distorts (the wingtip warps backwards)
  • the right brake pressure softens
  • you feel a sideslip on the yaw axis

And also:

  • the wing deflates
  • you feel a slight imbalance in the harness

 

Release both brakes immediately, quickly and completely: “hands up!”

The goal is to not deviate from your heading (less than 45° heading change).
 

Let the wing begin its surge (aerodynamic surge)…

Catching the surge:

Most of the time catching is not necessary.
But the greater the heading change, the more strong the surge will be.

Wait until the wing is at least 30° forward before braking.
The braking is like a brake pump:

  • A very quick gesture!
  • About 50 cm amplitude.
  • Not held: very short duration!
  • Released quickly and completely…

 

Warning! The wing is very sensitive to dynamic stall when catching an aerodynamic surge.
 

Multiple attempts will be possible. Start with very short duration actions. As you practice, you’ll need to keep your hand low longer to create deeper asymmetric stalls (without deviating from your heading).

Be aware of the double sensation of an asymmetric stall:

  • the brake pressure softens
  • feeling of sideslip on the yaw axis.

 

Examples of asymmetric stalls:
 

 

Be careful not to unhook your reserve handle!
 
 

 

 

B – Avoidance Maneuver

Practice performing sharp turns between 1/4 and 1/2 turn, to avoid a collision.

Multiple attempts will be possible. It’s recommended to start with moderate direction changes. As you practice, you’ll need to turn more and more. The goal is to be able to make a 1/2 turn (but no more).

Initiating the maneuver

To create a surprise effect, David will indicate either “right!” or “left!”.
At the signal, bring down the brake sharply, quickly and completely on the indicated side.
 

If this sharp action causes an asymmetric stall:

  • the brake pressure softens
  • the wing turns very quickly on the yaw axis (sideslip)

 

Hold the brake down for at least 1/4 turn.
Release quickly and completely “hands up!”
Let the wing reinflate and begin its surge (aerodynamic surge).

Catching the surge:

The greater the heading change, the more dynamic the surge will be.

Wait until the wing is at least 30° forward before braking.
The braking is like a brake pump:

  • A very quick gesture!
  • About 50 cm amplitude.
  • Not held: very short duration!
  • Released quickly and completely…

 

Warning! The wing is very sensitive to dynamic stall when catching an aerodynamic surge.
 

Examples of successful avoidance maneuvers:

 

Sometimes this sharp action doesn’t cause an asymmetric stall. In this case, the brake pressure stays firm. You get a simple turn that might look like the beginning of a spiral. There’s no aerodynamic surge when releasing the brake, just a simple exit from rotation.

 

Examples where the wing doesn’t stall (simple turn):

 

 

C – Flight Incident in Turn

Practice feeling an asymmetric stall that occurs accidentally during a turn, and practice reacting correctly.

Choose a direction of rotation and start turning as if thermalling.

It’s possible to “cheat” by watching the wing for the first attempts. But the goal is to be able to feel the asymmetric stall without looking at the wing.

The wing should roll and turn.
You need to brake on the outside to prevent the wing from engage into a spiral (pitch angle).
On the turning side (= inside), the hand goes down slowly but more and more.
The more you brake inside, the more you need to dose the outside brake to prevent the wing from gaining speed.

If the wing enters a spiral (pitch angle and speed increase) abort! Hands up and exit the spiral…

Be aware of brake pressure…

After a while, and suddenly, the wing stalls on the turning side!

  • The brake pressure softens.
  • Feeling of sideslip on the yaw axis.
Release both brakes immediately: quick and complete hands up!

Warning! This exercise cannot be remote controlled. Don’t wait for David to say “hands up” or you’ll be 1/2 second late!

If you release immediately, there’s practically no surge. The longer you take to react, the stronger the surge will be!

Catching the surge:

The greater the heading change was, the more dynamic the surge will be.

Wait until the wing is at least 30° forward before braking.
The braking is like a brake pump:

  • a very quick gesture
  • about 50 cm amplitude
  • not held: very short duration
  • released quickly and completely.

 

Warning! The wing is very sensitive to dynamic stall when catching an aerodynamic surge.
 

Examples of asymmetric stalls in turns: