Deep Stall, Parachutal Stall or Parachutage
Sept 15, 2006 | Chapter 4, 19
When the wing is fully formed but slows down and starts dropping
vertically, it is in Parachutal Stall. Airflow on your face becomes nil and
the glider may start to spin.
Power aggravates the possibility as
does having an old glider, misrigged lines, high porosity and being light on
the glider. Older
designs were more prone to parachutal stall than newer designs.
The cure is to
immediately go hands up and reduce power. Most pilots won't have time for
the next steps which are: tweak the A's (palms forward, twist them down),
release the trimmers and step on the speedbar (if installed).
quite rare in free flight but, being light on an old glider is still asking
for it. That may have been what happened in the video
It's unfortunately quite common in motoring and is usually a
combination of slowing down with brakes, power, torque, turbulence and other factors. Most often it can be
attributed to being heavy handed. While it's properly called a
spin if a twisting develops but I consider the initiating stall
parachutal when the wing does not deform.
Regardless of the definition, the prevention is being very careful when applying brake
and the cure is getting off the throttle and reducing brake pressure. If you feel like you're
slowing down, reduce power and reduce pressure! And be very leery turning against your
motor's torque direction.
Here is a free flight stall so you can see that
it does happen, even without a motor.
In the video, you can see by the
trailing that he is not pulling any significant brake. Then the wing starts
descending vertically and stops flying forward as he swings a bit out in
front. The useless brake pull doesn't start until he's about to hit the
ground--more a reaction than anything else. Once near the ground, say within
50 feet, it is better NOT to try recovering since the glider will surge
forward and you will then free fall the last 30 feet--far worse.