I used just the basic drag data for a man published by
Horner many years ago. The drag area (CD*S) varies from
3 to 9 sq ft. Then I added a little lift, carefully
adjusted to give just the right amount of 'tracking'
ability. If anyone has better data I'd like to see it.
The arms move with the G or gear command because that
was easy to animate. There is a change in drag and in
pitch moment which has a slight effect on trim angle.
The legs move with the flap control. They change lift,
drag and pitch moment (trim angle). The / key deploys
the pilot chute which would pull out the Parafoil in
a real situation. The pilot chute is intended only as
a brief, temporary condition.
Steady Speeds at Various Positions:
Vertical Speed (fps):
________________Arm Position
_____________Fwd________Back
Legs Up____ -166 -191
Legs Down__ -118 -135
Total Speed (fps):
________________Arm Position
_____________Fwd________Back
Legs Up____ 166 193
Legs Down__ 123 146
This indicates with arms back and legs down the forward
speed was 55.6 fps and the glide ratio was 0.41.
(The glide ratio is the ratio of distance moved forward
to altitude lost.)
During the descent, the speed for any stable attitude
decreases gradually as the air density increases. The jumper
is supported by nearly 1 g of acceleration from the total
aerodynamic force. He is essentially in steady state. In
a jump from 20,000 ft to 8,000 ft, these speeds were
observed just below 15,000 ft. At the highest drag or
lowest speed position (arms fwd and legs down), stability
is low but you can hold that position if you work at it.
Roll control is used to determine heading of your glide.
Use a short pulse with the stick to start the motion and
then the opposite way to stop it.
