Using a collapsible pilot chute will improve the performance of your canopy. The increase in performance gained depends on the size of the canopy and the wing loading. It is a balance between the two, rather than wing loading or canopy size individually, as the pilot chute size generally remains constant rather than reducing with the canopy size.
There are two types of collapsing systems in common use; the ‘kill line’ system and the ‘bungee’ system. We prefer the kill line, however, the bungee is easier to operate and requires less packing.
If you are using a class 3 or below (eg below 1.25 PSF) or canopies above 160 sf, this gain will be minimal and possibly not worth the complication (as in a student canopy situation). For Class 4 (1.25-1.65 PSF), or canopies between 160 and 120 sf, we recommend a collapsible pilot chute. Either a bungee system or a kill line is OK. For Class 5 and above (above 1.65 sf), and canopies below 120 sf, it is a a necessity. This situation requires a kill line, rather than a bungee, as the speeds you can reach leave a smaller range between a subterminal opening and a hell of acanopy swoop.
On small canopies, collapsing the pilot chute has a double effect. Firstly, the drag of the pilot chute has gone and secondly, when the pilot chute is inflated, it will drag the center of the canopy back – putting a slight ‘V’ in the canopy planform. This ‘V’ configuration increases the canopy drag considerably, as the flow of air is no longer running directly down the cell (which is relatively smooth), but at an angle across it (which is very rough due to the cells bulging between the ribs).
Imagine the cross section of a canopy at any point, then imagine the cross section 10 degrees off true – this should illustrate the need for a collapsing pilot chute in this situation.
Another effect of an inflated pilot chute is to reduce the canopy’s recovery arc. On a highly loaded canopy with a large recovery arc, this arc may be reduced by as much as 30%, by pulling the canopy up short and not letting it dive for very long. This becomes especially relevant in two situations:
- If you have been flying your canopy with an inflated pilot chute, then put a collapsing system on, you will need to increase the height of your hook turn as your canopy will be diving more and require more time to recover. This is a potentially dangerous trap. You will also be coming in faster horizontally, as your canopy will have accelerated more through this longer recovery arc and through less drag. It will be behaving like a smaller canopy.
- If you are using a bungee system that may or may not stay collapsed during your swoop, you will have lost control of the height that your recovery arc will level out at. This is especially problematical if your pilot chute has been inflating behind you, without you knowing.