SIGMA TANDEM SYSTEM OWNER’S MANUAL
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Section 2: Equipment • Chapter 1 - Description 11301 - 00.00.0000
THE SIGMA DROGUE COLLAPSE SEQUENCE
The collapse sequence on the Sigma drogue is the same as on previous Vector drogues. The drogue partially collapses,
at a controlled rate during bag lift-off, yielding just the right amount of force for an orderly deployment. However, the
method of collapse is slightly different.
The drogue bridle and kill line now both end at the same place, a rapid link connected to the top of the deployment
bag. When the drogue is set (or cocked) during the packing sequence, the Kevlar drogue bridle below the disk is
“scrunched up”, effectively making the bridle shorter than the kill line. When the drogue is deployed, it can inflate
because the kill line is longer than the bridle. When a ripcord is pulled to end droguefall, the container opens and the
disk is released, allowing the “scrunched up” section of the bridle below the disk to extend to its full length, thus
making the bridle longer than the kill line. This inverts the drogue apex, collapsing the drogue.
Because both the drogue bridle and kill line are made of non-stretch materials, the drogue collapse sequence is
“stopped” automatically, at just the right point. No ring, slamming into a “stop ring” at high speed is needed, and the
bridle moves over the kill line for a much shorter distance than on the previous design. This means less friction is
generated, so everything lasts longer. And with no stop ring, the kill line is much less complicated and easier to
replace. Also, because both the drogue bridle and kill line end at the same place, it is impossible to twist one independent
of the other. This means no more time consuming untwisting of the kill line at pack time.
HOW TO CHECK IF YOUR DROGUE KILL LINE IS THE CORRECT
LENGTH
For this system to work correctly, a precise relationship between the length of the drogue bridle and the length of the
kill line must be maintained. To check this relationship:
Anchor the rapid link at the deployment bag end of the drogue bridle. Both the drogue bridle and kill line should be
connected to this link.
Extend the drogue bridle fully.
Put a finger on either side of the kill line guide grommet at the base of the drogue, and apply about 10 lbs. of tension
against the Kevlar bridle.
With the other hand apply the same tension on the kill line by pulling on the kill line attachment bridle or the drogue
handle. The larks head knot at the bottom of the kill line attachment bridle should be 1½ ” above the kill line guide
grommet.
You can notice this relationship less formally each time you pick up your drogue after landing.
If this distance is more than 2” greater, the drogue may not fully collapse, yielding a higher snatch force, increased
chance of malfunction due to line dump, and increased chance of canopy damage. If you notice a kill line that is over
2” too long, a simple overhand knot, tied within the finger-locked section of the kill line, at the deployment bag end, will
effectively shorten it almost 2”, and bring your drogue collapse system back into trim.
If this distance is more than 1” less, the larks head knot will impact the guide grommet at high speed, quickly causing
damage to both. However, in this instance, deployment, while slightly slower, will still happen more or less normally.
Drouge collapse is calibrated for average weight and fall rates, if you feel the drouge is collapsing to far with longer
than normal “trap door” you may Larkshead a PD Slink onto the bottom of the kill line to reduce the amount of
collapse.
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