Unknown Armies:Skill Checks
Minor skill checks
For minor skill checks, you need a 15% or higher skill rating for an automatic success—no dice needed. These are situations where you have plenty of time and no risk, like taking a photograph of your house or reading up on Greek history.
Significant skill checks
Higher skill levels are important for significant skill checks. These happen when you aren't in an intense situation such as combat, but there's still some pressure on you or what you're doing has a high element of uncertainty. Spending a day hacking an unfamiliar operating system, keeping an eye on your husband in a big crowd, or studying for a weekly test could qualify. For these tasks, you have a strong success if you roll under your skill level. If you fail the roll, you get a weak success if that roll is still under the related stat. You only fail completely if you roll above your stat.
Major skill checks
Major skill checks are the big ones, and in the occult underground they happen all the time. All combat rolls are major checks, as are any actions you attempt under stress and risk. If it really matters, it's a major check.
Unskilled Actions
Sometimes you need to do things that you don't know how to do—you don't have the right skill, or even the right skill penumbra. You may be in luck if the dice are on your side.
For minor and significant skill checks, you can roll against the appropriate stat. But your stat has a -30 shift. If you make it, you succeed but only barely—pat yourself on the back and next time, find somebody who knows what she's doing.
For major checks, you can roll a Hail Mary against the appropriate stat. Only matched successes and crits succeed. You don't get to treat the results as a match or a crit, either—they just give you a half-assed, marginal success.
Any unskilled failure is unusually bad. The GM comes up with an appropriate screw job as you bumble your way to disaster.
But some things are just plain impossible. Even if you have all day to sit in the cockpit of an F-15, humming to yourself and pushing buttons in relaxed comfort, you're just not going to get it off the ground.