The trimmers are one of the basic controls. Despite the fact that principles of their operation are broadly understood, we need to underline some basic safety rules.
The trimmers are always to be released (activated) symmetrically. Full release of just the left or right one will cause the paraglider to enter a turn, and in extreme cases even a spiral. Reaction time can be vary a lot, depending on the paraglider model and current take-off weight (the greater weight, the faster reactions).
The only justified exception from the rule of symmetric trimmers operation are minor differences needed for flight path corrections.
When you want to open the trimmers, use following procedure:
a/ take trimmer buckles in your hands,
b/ press the blocking parts with your thumbs,
c/ when you feel both locks to ease, allow the risers to slip out.
In this way you will be able to release your trimmers exactly how much you wanted to, with full control over the process.
When pulling the trimmers in, do it symmetrically as well.
Activate the trimmers at safe altitude, to have some margin for corrections in case of an error.
If you happen to release the trimmer not symmetrically:
a/ correct your heading with a brake,
b/ release the other trimmer (altitude permitting), or close the released one.
Power Attack system is a steering system component, automatically merging action of the speed system and the trimmers. Lines and pulleys of both the speed and PowerAttack systems have to be visually checked during each launch preparation. Accidental breaking a Power Attack line can bring about a situation equivalent to asymmetric release of one trimmer!