Using a collapsible pilot chute will improve the performance of your canopy. The increase in performance you will gain 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 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 (below 1.25 PSF) or canopies above 160 sf this gain will be minimal and possibly not worth the complication (like 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 pretty much a necessity. This situation should be used with a kill line rather than a Bungee as the speeds you can reach are leaving a smaller range between a subterminal opening and a hell canopy swoop.
On small canopies collapsing the pilotchute has a double effect, first 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 and you will understand the need for a collapsing pilot chute in this situation.
Another effect an inflated pilot chute has is to reduce the canopies recovery arc. On a highly loaded canopy with a large recovery arc it may reduce the arc be as much as 30% by pulling the canopy up short and not letting the canopy dive for very long. This becomes especially relevant in two situations. 1) If you have been flying your canopy with an inflated pilotchute 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 (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 behaving like a smaller canopy). 2) If you are using a Bungee system that may or may not stay collapsed during your swoop you have now lost control of the height that your recovery arc will level out at, especially a problem if your pilot chute has been inflating behind you without you knowing.