How to throw your reserve in a SAT


(Kristopher Holub) #1

We had an interesting and long conversation yesterday on the boulder whatsapp chat (apologies to those who sat through my endless messages) which I wanted to preserve here. The question started off being largely about where the best place to aim your reserve throw should be to minimize the chances of reserve entanglement.

Short answer: Throw the reserve as hard as you possibly can towards and slightly above the horizon WITH the G-forces. In an autorotation this direction will be more towards your feet. In a flat spin or stall, it will be off to your side. NEVER throw it at the ground or in the direction that your lines run towards your canopy ( which is towards the G forces)

Here’s my analysis:

First, it is important to understand the distinction between a spiral and a SAT. The most important difference is that a spiral rotates about an axis “above” the canopy, and a SAT rotates about an axis somewhere between the canopy and the pilot. See below, where in each case the glider rotates about an axis coming perpendicular out of the screen at the blue bullseye. The glider and lines sweep an area outlined in red as it descends vertically (into the screen). This “keep out” area is a huge risk to reserve entanglement, so the goal is to get the reserve outside of it as quickly as possible, reaching line stretch and deploying before something can foul it

Spiral:

Sat:

Note that what makes a SAT particularly dangerous is that you are inside of the keep out zone and the reserve has to make it outside before something catches it. In a spiral, you are outside in “clean” air so a successful deployment is much more likely.

In a spiral, the decision is easy. You throw to the outside of the spiral and the g forces carry the reserve into clean air. If the G forces are high your throw almost doesnt matter, it will deploy very rapidly.

In a sat, the conventional wisdom is to “throw at the trialing edge of the glider”, the rationale being that the glider will not be there by the time the reserve arrives. What is wrong about this advice is that (1) in doing so you are throwing against the G forces and (2), your body is accelerating into this direction, which puts slack into the reserve bridle and delays the opening, and (3) the reserve must traverse a longer path through the keep out zone, increasing the risk of entanglement. In the event of a weak throw, the wing will make it all the way around and catch the reserve anyway before it clears the keep out zone.

Bad SAT throw
Sat%20throw%20bad

In contrast, if you throw in the “same” direction as a spiral, the G forces work in your favor to stretch the bridle out and get the reserve open. Yes, the glider will be “closer” to the reserve, but it doesnt matter if the reserve is already at line stretch and opening. Plus in a good throw, it will be outside of the keep out area.

Good SAT throw
Sat%20throw%20good

The tricky party is identifying the right location. In a high stress situation it is exceedingly difficult to process visual information, so its best to have a simple plan that you can execute reliably. Whenever the g forces are high, your feet will be pointing roughly towards the horizon, so the throw direction is generally towards your feet. In a slower speed malfunction such as a stall or spin, the g forces are lower and the correct direction to throw relative to your body is sideways. In both cases the reserve still goes out towards the horizon, away from the vertical keep out column.