Hang Gliding and Paragliding Volume 44 / Issue 2: February 2014 | Page 37

HG401

Advanced Techniques & Concepts

Pushing

OU T
by

I

t’s easy to define the (only) two times when less
experienced pilots should push out—when they want
to land (flare) and when they want to crash. Pushing
out reduces airspeed by raising the angle of attack of
our wing, which drastically impacts the roll response of
our glider and hinders in-flight lateral control. New and
low-airtime pilots should be flying forgiving single-surface
wings, which do a great job of finding the appropriate
“trim” position and speed for nearly every situation.

R YA N V OIG H T

attack and fly faster, more of the wing actually sees a negative
angle of attack, shortening the effective wingspan of a glider.
This is pretty complex and something fairly unique to hang
gliders. But changes in effective wingspan can have a HUGE
impact on handling. In simple terms, shorter wings roll easier.
Loss of lateral control isn’t even the biggest risk in pushing
out. The more you push out, the easier it is for your glider
to tumble. Again, the cause is two-fold. First, pushing out
changes the center of mass of the wing. There is a direct

“As we decrease our angle of attack and fly faster,
more of the wing actually sees a negative angle of
attack, shortening the effective wingspan of a glider.”
However, some advanced techniques involve pushing
out. I will describe a few, but first, I would like to identify
some risks involved. The first and most obvious is the greatly
reduced lateral control that accompanies pushing out. The
cause of this is two-fold: The more air we have flowing over
our wings, the more force the same amount of “deflection” is
created in the sail. (Easy example: sticking your hand out the
car window at 20 mph compared to 80 mph: more airflow,
more force.) The less recognized factor comes from flying
tail-less aircraft and having swept wings with washout, where
the tips are at a much lower angle of attack than the center
of the wing. When we push out and fly very slowly, more of
the wing is at a positive angle of attack, making the effective
wingspan of the glider larger. As we decrease our angle of

relationship between center of mass and pitch stability. A
simple example is a dart (heavy at one end, very light with
lots of drag at the other). No matter how you throw a dart, it
will eventually stabilize in a “nose down” orientation. The opposite example is a sheet of paper; each side is balanced, with
equal weight and equal drag. Hold up a sheet of paper and
drop it, and it will not stabilize in any particular orientation
at all. Pulling in, in a hang glider, drastically increases pitch
stability, while pushing out reduces it considerably. It does
not matter if a glider is certified to be “pitch stable”; when you
push out, you alter the stability.
The other factor that increases the risk of tumble comes
from the very low airspeed associated with pushing out and
how our pitch-stability systems work. Pitch-stability systems

OPPOSITE Pushing out