Pilot Chute Hesitation

 

How do skydivers deploy their main canopies ? The first thing that comes on non-jumper's mind is "pulling a ring". Even though it is true for student and reserve parachutes, regular skydivers use enother method. Pilot chute is simply stowed in the bottom of the container. It is completely hidden inside with an exception of one little handle sticking out :

 

When it's time to deploy, you simply grab the handle, pull the pilot chute out, and throw it to the air. Pilot chute is connected to the bridle, which is linked to the canopy on its other side(actually, to the bag which has the parachute in it, to be excact).

Some calculations :

A pilot chute with radius R=34 cm at the terminal speed will have a drag

d=(1/2))CpAv^2, where C- drag coefficient (varies from 0.4 to 1.0), p- density of the air(1 kg/m^3), v is velocity, and A is effective cross-section.

d= (1/2)(.8)(1kg/m^3)(.34m)^2(3.14)(50m/s)^2 = 363 N

But here is the potential problem. A skydiver falling at a big speed necessary has an area of low pressure behind his back. Density of the air in that area is significally lower, which does not provide enough drag force in order to lift the parachute.

 

Two things can be done to prevent this malfunction. When you pull the pilot chute out, do not just let it go, but throw it to the side, where there is enough air. If hesitation happened, turn to your side, and the air pressure would increase.